bldc motor, esc and battery draw, nominal vs peakHow to size wire gauge for BLDC motorMaking ESC for RC truck; Max motor Amp unkownCan small wire gauge restrict current? powering a brushless motorHow to drop voltage in a variable amperage 48 vdc ebike motor circuitIdentifying the bottleneck component in a Quadcopter build [Jerking motors]What does changing the throttle to a BLDC ESC actually do?Can I use this BLDC controller for RC motor for friction drive eBike?What's the meaning of current rating of BLDC motor and it's relation to a phase peak and RMS current?Why does my BLDC motor change behavior at high speed?I have designed and 3D printed a new motor that was based on a video i saw earlier, however motor keeps stuttering and wont turn, what went wrong?
Endgame puzzle: How to avoid stalemate and win?
Why did WWI include Japan?
Disabling quote conversion in docstrings
Looking for sci-fi book based on Hinduism/Buddhism
Where did Lovecraft write about Carcosa?
Game artist computer workstation set-up – is this overkill?
Is there a word that describes the unjustified use of a more complex word?
Why does blending blueberries, milk, banana and vanilla extract cause the mixture to have a yogurty consistency?
Why does sound not move through a wall?
Meaning of the (idiomatic?) expression "seghe mentali"
All superlinear runtime algorithms are asymptotically equivalent to convex function?
What happens if I accidentally leave an app running and click "Install Now" in Software Updater?
How did the Apollo guidance computer handle parity bit errors?
Madam I m Adam..please don’t get mad..you will no longer be prime
Why would a military not separate its forces into different branches?
Should homeowners insurance cover the cost of the home?
no sense/need/point
Should I simplify my writing in a foreign country?
Make me a minimum magic sum
Would a small hole in a Faraday cage drastically reduce its effectiveness at blocking interference?
Is disk brake effectiveness mitigated by tyres losing traction under strong braking?
How to remap repeating commands i.e. <number><command>?
Has the Hulk always been able to talk?
Dangerous workplace travelling
bldc motor, esc and battery draw, nominal vs peak
How to size wire gauge for BLDC motorMaking ESC for RC truck; Max motor Amp unkownCan small wire gauge restrict current? powering a brushless motorHow to drop voltage in a variable amperage 48 vdc ebike motor circuitIdentifying the bottleneck component in a Quadcopter build [Jerking motors]What does changing the throttle to a BLDC ESC actually do?Can I use this BLDC controller for RC motor for friction drive eBike?What's the meaning of current rating of BLDC motor and it's relation to a phase peak and RMS current?Why does my BLDC motor change behavior at high speed?I have designed and 3D printed a new motor that was based on a video i saw earlier, however motor keeps stuttering and wont turn, what went wrong?
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
$begingroup$
I want to better understand how Electronic Speed Controllers (ESC) work for BLDC motors. Specifically, I am trying to understand battery current draw.
Question 1:
When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Question 2:
If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that? I'm now thinking the draw will be more along the RMS value of the output pulse wave. This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
Question 3: (slightly off topic)
To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear. I just want to understand the theory of how ESC's work at a high level.
Much thanks!
current brushless-dc-motor motor-controller
asked Apr 26 at 16:30
twegnertwegner
111
$endgroup$
add a comment |
$begingroup$
I want to better understand how Electronic Speed Controllers (ESC) work for BLDC motors. Specifically, I am trying to understand battery current draw.
Question 1:
When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Question 2:
If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that? I'm now thinking the draw will be more along the RMS value of the output pulse wave. This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
Question 3: (slightly off topic)
To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear. I just want to understand the theory of how ESC's work at a high level.
Much thanks!
current brushless-dc-motor motor-controller
asked Apr 26 at 16:30
twegnertwegner
111
$endgroup$
$begingroup$
"When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC." - the 'silicone' insulation used on most ESC wires can handle higher temperature than PVC, so the current rating is higher, eg. 180A for 8AWG 4-max.co.uk/silicone-wire.htm
$endgroup$
– Bruce Abbott
Apr 27 at 0:50
add a comment |
$begingroup$
I want to better understand how Electronic Speed Controllers (ESC) work for BLDC motors. Specifically, I am trying to understand battery current draw.
Question 1:
When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Question 2:
If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that? I'm now thinking the draw will be more along the RMS value of the output pulse wave. This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
Question 3: (slightly off topic)
To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear. I just want to understand the theory of how ESC's work at a high level.
Much thanks!
current brushless-dc-motor motor-controller
asked Apr 26 at 16:30
twegnertwegner
111
$endgroup$
I want to better understand how Electronic Speed Controllers (ESC) work for BLDC motors. Specifically, I am trying to understand battery current draw.
Question 1:
When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Question 2:
If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that? I'm now thinking the draw will be more along the RMS value of the output pulse wave. This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
Question 3: (slightly off topic)
To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear. I just want to understand the theory of how ESC's work at a high level.
Much thanks!
current brushless-dc-motor motor-controller
current brushless-dc-motor motor-controller
asked Apr 26 at 16:30
twegnertwegner
111
asked Apr 26 at 16:30
twegnertwegner
111
asked Apr 26 at 16:30
twegnertwegner
111
asked Apr 26 at 16:30
twegnertwegner
111
asked Apr 26 at 16:30
twegnertwegner
111
111
$begingroup$
"When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC." - the 'silicone' insulation used on most ESC wires can handle higher temperature than PVC, so the current rating is higher, eg. 180A for 8AWG 4-max.co.uk/silicone-wire.htm
$endgroup$
– Bruce Abbott
Apr 27 at 0:50
add a comment |
$begingroup$
"When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC." - the 'silicone' insulation used on most ESC wires can handle higher temperature than PVC, so the current rating is higher, eg. 180A for 8AWG 4-max.co.uk/silicone-wire.htm
$endgroup$
– Bruce Abbott
Apr 27 at 0:50
$begingroup$
"When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC." - the 'silicone' insulation used on most ESC wires can handle higher temperature than PVC, so the current rating is higher, eg. 180A for 8AWG 4-max.co.uk/silicone-wire.htm
$endgroup$
– Bruce Abbott
Apr 27 at 0:50
$begingroup$
"When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC." - the 'silicone' insulation used on most ESC wires can handle higher temperature than PVC, so the current rating is higher, eg. 180A for 8AWG 4-max.co.uk/silicone-wire.htm
$endgroup$
– Bruce Abbott
Apr 27 at 0:50
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Without a datasheet we're guessing but the 500 A peak current is likely to occur during start-up and this may last one or more tenths of a second. A capacitor to supply 500 A for 0.1 s at a useful voltage will be very large.
It's much more likely that any capacitors on the DC input stage are acting as short-term filters to pass high-frequency noise to ground.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
It will need to draw enough to power the motor. It completely depends on the load the motor is given.
This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
This may be a warning sign that you have a low quality product.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear.
The ESC will operate using pulse-width modulation (PWM) as it results in very low losses in the switching transistors. PWM applies pulses of 100% voltage to the motor for a short period, switches off, waits and then repeats the process.
Figure 1. PWM signal transitioning from high pulse width (75%) to low (25%) and back again. Note amplitude remains constant.
answered Apr 26 at 16:41
TransistorTransistor
90.6k788195
$endgroup$
$begingroup$
Q2 "It completely depends on the load the motor is given". Would that not be the nominal 200 amp rating? Assuming it is, would it then be drawing the RMS of the PWM wave? Also, you are likely correct that I have a low quality product, thanks for raising this point.
$endgroup$
– twegner
Apr 26 at 16:50
$begingroup$
Both the question and to some degree this attempted answer are making the fundamental mistake of assuming that the rating is a current draw. It is not, rather it is a "rating" (likely overly optimistic) of what the FETs on the ESC can handle. This has nothing to do with what the circuit may draw, which might be far less in proper operation, or substantially more in misapplication, leading to failure of whatever part of the installation is weakest (hopefully a user-provided fuse).
$endgroup$
– Chris Stratton
Apr 26 at 17:20
$begingroup$
@twegner: What I'm saying is that the load on the motor (bike going up a hill, winch lifting a load, etc.) determines the current requirement. If there is a light load then the current will be reduced. The maximum load that you can drive will be determined by the motor limit or ESC limit - whichever is the lower.
$endgroup$
– Transistor
Apr 26 at 18:00
$begingroup$
@Transistor: Yes, I understand. I should have phrased that as Max Throttle and full load - like heavy acceleration against a high resistance. So in this case, I assume the 200 amp nominal rating is what is being output (if that - according to Chris Stratton) from the ESC to the motor.
$endgroup$
– twegner
Apr 26 at 18:50
$begingroup$
@ChrisStratton: I didn't mean to imply the ESC rating is current draw. Rather I was questioning if the ESC's 200 amp output is what I should expect to be pulled from the battery pack or if it was more along the lines of the RMS of the output that would be pulled from the battery. Thanks for you input. Again, I was just looking for some high level theory, so this helps.
$endgroup$
– twegner
Apr 26 at 18:56
add a comment |
$begingroup$
All answers assume you're talking about "hobby" ESCs, as used in planes, boats, cars, robots, etc.
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps?
No. For the most part, the ESC draws what it draws given the motor, battery and load on the motor.
Some of the better ESC's do have current limiting, but experience in the flying field is that if you dork the thing into the dirt at full throttle, chances are that you'll damage the electronics due to overcurrent.
An ESC could be designed to limit current in such a way (I've designed industrial motor controllers that do), but AFAIK ESC's don't.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
See answer to question 1.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage?
Neither. At the level of the throttle command to motor, it supplies a fixed PWM to the motor -- essentially it chops the battery voltage and hands it to the motor.
This is complicated by the fact that some ESC's have a governor function, that servos the motor speed to the signal coming in -- but they still have an internal throttle command that works as above.
answered Apr 26 at 16:52
TimWescottTimWescott
7,5391417
$endgroup$
$begingroup$
Your Q3 response. I'm trying to understand this better. Are you saying the current is fixed and that the PWM is just shortened? (Like Transistors PWM graph) Basically the duty cycle is reduced but the current is not, but essentially this means less power is used.
$endgroup$
– twegner
Apr 26 at 19:08
$begingroup$
The PWM duty cycle is fixed by the "throttle" command. Cheaper ESCs don't even have a current sensor (other than the current-to-smoke converters that come free with every power electronics device in the world).
$endgroup$
– TimWescott
Apr 26 at 22:12
add a comment |
$begingroup$
The max operating temperature or heat rise above 25'C is what limits the nominal continuous current rating. The peak is an absolute maximum which may or may not be protected and should never be exceeded, such as starting a couple of these motors below at full throttle.
One must mind the rated peak currents to prevent damage to the electronics.
Similarily, a motor full load current rating is defined by the same method of temperature rise above 25'C for the winding hot spots. However every market does not use the same hot spot temperature for a long useful life and if no standards are given or not temp rise is specified, you might guess they don't want you to know.
However it is quite common to give the peak motor current as surge, start or locked rotor current. These are all the same as is simply Ohm's Law applied to the DC resistance or DCR, so Imax= V/DCR. This is typically Imax = 8 to 12 times the rated current in modern BLDC, high-efficiency DC motors.
Here they generously rate the motor current with a 180 second limit. This would be at max internal temperature.
answered Apr 26 at 18:49
Sunnyskyguy EE75Sunnyskyguy EE75
72.9k228103
$endgroup$
$begingroup$
If I'm reading the Tech sheet right, they are doing P=IV, so 885.4 watts = 4.2 vdc (not 3.7) * 4 cells * 52.7 amps. I understand your locked rotor 360 amp (V/R=I) calculation. So are you saying that as soon as the rotor locks, like if the parking brake was on (just go with it), that this motor should be paired with an ESC that can handle at least 360 amps? Which is way more than the Max Current on the spec sheet indicates. Also, thanks for providing a real world example. Yours and all the other answers are beginning to clear up my muddy understanding of this.
$endgroup$
– twegner
Apr 26 at 19:34
$begingroup$
The 885W is the motor power doing work if the batteries did not drop from a full charge at 4.2V for 120s, which seems unlikely even if they were 8P4S arrays as I believe it would drop to 3.6V at this current @ 120s. The 113 watts I calculated is DCR loss that makes the inefficiency 12.8% = 113/885W that produces heat while accelerating or braking until speed induced BEMF reduces the net voltage across the winding. So the ESC must use current feedback to regulate constant current to match this motor spec. limit. I expect ESC current-mode feedback limits torque and voltage regulates speed.
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:43
$begingroup$
I would expect an ESC of this caliber to have current limit control and voltage control. But I can't say for sure. AWG8= 2 mohm/m or 4mOhm/m pair
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:45
add a comment |
Your Answer
StackExchange.ifUsing("editor", function ()
return StackExchange.using("schematics", function ()
StackExchange.schematics.init();
);
, "cicuitlab");
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "135"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f435606%2fbldc-motor-esc-and-battery-draw-nominal-vs-peak%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Without a datasheet we're guessing but the 500 A peak current is likely to occur during start-up and this may last one or more tenths of a second. A capacitor to supply 500 A for 0.1 s at a useful voltage will be very large.
It's much more likely that any capacitors on the DC input stage are acting as short-term filters to pass high-frequency noise to ground.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
It will need to draw enough to power the motor. It completely depends on the load the motor is given.
This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
This may be a warning sign that you have a low quality product.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear.
The ESC will operate using pulse-width modulation (PWM) as it results in very low losses in the switching transistors. PWM applies pulses of 100% voltage to the motor for a short period, switches off, waits and then repeats the process.
Figure 1. PWM signal transitioning from high pulse width (75%) to low (25%) and back again. Note amplitude remains constant.
answered Apr 26 at 16:41
TransistorTransistor
90.6k788195
$endgroup$
$begingroup$
Q2 "It completely depends on the load the motor is given". Would that not be the nominal 200 amp rating? Assuming it is, would it then be drawing the RMS of the PWM wave? Also, you are likely correct that I have a low quality product, thanks for raising this point.
$endgroup$
– twegner
Apr 26 at 16:50
$begingroup$
Both the question and to some degree this attempted answer are making the fundamental mistake of assuming that the rating is a current draw. It is not, rather it is a "rating" (likely overly optimistic) of what the FETs on the ESC can handle. This has nothing to do with what the circuit may draw, which might be far less in proper operation, or substantially more in misapplication, leading to failure of whatever part of the installation is weakest (hopefully a user-provided fuse).
$endgroup$
– Chris Stratton
Apr 26 at 17:20
$begingroup$
@twegner: What I'm saying is that the load on the motor (bike going up a hill, winch lifting a load, etc.) determines the current requirement. If there is a light load then the current will be reduced. The maximum load that you can drive will be determined by the motor limit or ESC limit - whichever is the lower.
$endgroup$
– Transistor
Apr 26 at 18:00
$begingroup$
@Transistor: Yes, I understand. I should have phrased that as Max Throttle and full load - like heavy acceleration against a high resistance. So in this case, I assume the 200 amp nominal rating is what is being output (if that - according to Chris Stratton) from the ESC to the motor.
$endgroup$
– twegner
Apr 26 at 18:50
$begingroup$
@ChrisStratton: I didn't mean to imply the ESC rating is current draw. Rather I was questioning if the ESC's 200 amp output is what I should expect to be pulled from the battery pack or if it was more along the lines of the RMS of the output that would be pulled from the battery. Thanks for you input. Again, I was just looking for some high level theory, so this helps.
$endgroup$
– twegner
Apr 26 at 18:56
add a comment |
$begingroup$
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Without a datasheet we're guessing but the 500 A peak current is likely to occur during start-up and this may last one or more tenths of a second. A capacitor to supply 500 A for 0.1 s at a useful voltage will be very large.
It's much more likely that any capacitors on the DC input stage are acting as short-term filters to pass high-frequency noise to ground.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
It will need to draw enough to power the motor. It completely depends on the load the motor is given.
This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
This may be a warning sign that you have a low quality product.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear.
The ESC will operate using pulse-width modulation (PWM) as it results in very low losses in the switching transistors. PWM applies pulses of 100% voltage to the motor for a short period, switches off, waits and then repeats the process.
Figure 1. PWM signal transitioning from high pulse width (75%) to low (25%) and back again. Note amplitude remains constant.
answered Apr 26 at 16:41
TransistorTransistor
90.6k788195
$endgroup$
$begingroup$
Q2 "It completely depends on the load the motor is given". Would that not be the nominal 200 amp rating? Assuming it is, would it then be drawing the RMS of the PWM wave? Also, you are likely correct that I have a low quality product, thanks for raising this point.
$endgroup$
– twegner
Apr 26 at 16:50
$begingroup$
Both the question and to some degree this attempted answer are making the fundamental mistake of assuming that the rating is a current draw. It is not, rather it is a "rating" (likely overly optimistic) of what the FETs on the ESC can handle. This has nothing to do with what the circuit may draw, which might be far less in proper operation, or substantially more in misapplication, leading to failure of whatever part of the installation is weakest (hopefully a user-provided fuse).
$endgroup$
– Chris Stratton
Apr 26 at 17:20
$begingroup$
@twegner: What I'm saying is that the load on the motor (bike going up a hill, winch lifting a load, etc.) determines the current requirement. If there is a light load then the current will be reduced. The maximum load that you can drive will be determined by the motor limit or ESC limit - whichever is the lower.
$endgroup$
– Transistor
Apr 26 at 18:00
$begingroup$
@Transistor: Yes, I understand. I should have phrased that as Max Throttle and full load - like heavy acceleration against a high resistance. So in this case, I assume the 200 amp nominal rating is what is being output (if that - according to Chris Stratton) from the ESC to the motor.
$endgroup$
– twegner
Apr 26 at 18:50
$begingroup$
@ChrisStratton: I didn't mean to imply the ESC rating is current draw. Rather I was questioning if the ESC's 200 amp output is what I should expect to be pulled from the battery pack or if it was more along the lines of the RMS of the output that would be pulled from the battery. Thanks for you input. Again, I was just looking for some high level theory, so this helps.
$endgroup$
– twegner
Apr 26 at 18:56
add a comment |
$begingroup$
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Without a datasheet we're guessing but the 500 A peak current is likely to occur during start-up and this may last one or more tenths of a second. A capacitor to supply 500 A for 0.1 s at a useful voltage will be very large.
It's much more likely that any capacitors on the DC input stage are acting as short-term filters to pass high-frequency noise to ground.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
It will need to draw enough to power the motor. It completely depends on the load the motor is given.
This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
This may be a warning sign that you have a low quality product.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear.
The ESC will operate using pulse-width modulation (PWM) as it results in very low losses in the switching transistors. PWM applies pulses of 100% voltage to the motor for a short period, switches off, waits and then repeats the process.
Figure 1. PWM signal transitioning from high pulse width (75%) to low (25%) and back again. Note amplitude remains constant.
answered Apr 26 at 16:41
TransistorTransistor
90.6k788195
$endgroup$
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps? I'm rationalizing this in my head by assuming the capacitors in the ESC are just discharging more current than normal for short durations when this 'peak' value is experienced. I'm also assuming it will never try to pull 500 amps from the battery pack. If this isn't right, please explain.
Without a datasheet we're guessing but the 500 A peak current is likely to occur during start-up and this may last one or more tenths of a second. A capacitor to supply 500 A for 0.1 s at a useful voltage will be very large.
It's much more likely that any capacitors on the DC input stage are acting as short-term filters to pass high-frequency noise to ground.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
It will need to draw enough to power the motor. It completely depends on the load the motor is given.
This would explain why the ESC input wires from the battery pack are relatively small in relation to the output current rating. When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC.
This may be a warning sign that you have a low quality product.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage? I assume it is current, I just want verification. Let's say the throttle is at 10% and assume the throttle curve is linear.
The ESC will operate using pulse-width modulation (PWM) as it results in very low losses in the switching transistors. PWM applies pulses of 100% voltage to the motor for a short period, switches off, waits and then repeats the process.
Figure 1. PWM signal transitioning from high pulse width (75%) to low (25%) and back again. Note amplitude remains constant.
answered Apr 26 at 16:41
TransistorTransistor
90.6k788195
answered Apr 26 at 16:41
TransistorTransistor
90.6k788195
answered Apr 26 at 16:41
TransistorTransistor
90.6k788195
answered Apr 26 at 16:41
TransistorTransistor
90.6k788195
90.6k788195
$begingroup$
Q2 "It completely depends on the load the motor is given". Would that not be the nominal 200 amp rating? Assuming it is, would it then be drawing the RMS of the PWM wave? Also, you are likely correct that I have a low quality product, thanks for raising this point.
$endgroup$
– twegner
Apr 26 at 16:50
$begingroup$
Both the question and to some degree this attempted answer are making the fundamental mistake of assuming that the rating is a current draw. It is not, rather it is a "rating" (likely overly optimistic) of what the FETs on the ESC can handle. This has nothing to do with what the circuit may draw, which might be far less in proper operation, or substantially more in misapplication, leading to failure of whatever part of the installation is weakest (hopefully a user-provided fuse).
$endgroup$
– Chris Stratton
Apr 26 at 17:20
$begingroup$
@twegner: What I'm saying is that the load on the motor (bike going up a hill, winch lifting a load, etc.) determines the current requirement. If there is a light load then the current will be reduced. The maximum load that you can drive will be determined by the motor limit or ESC limit - whichever is the lower.
$endgroup$
– Transistor
Apr 26 at 18:00
$begingroup$
@Transistor: Yes, I understand. I should have phrased that as Max Throttle and full load - like heavy acceleration against a high resistance. So in this case, I assume the 200 amp nominal rating is what is being output (if that - according to Chris Stratton) from the ESC to the motor.
$endgroup$
– twegner
Apr 26 at 18:50
$begingroup$
@ChrisStratton: I didn't mean to imply the ESC rating is current draw. Rather I was questioning if the ESC's 200 amp output is what I should expect to be pulled from the battery pack or if it was more along the lines of the RMS of the output that would be pulled from the battery. Thanks for you input. Again, I was just looking for some high level theory, so this helps.
$endgroup$
– twegner
Apr 26 at 18:56
add a comment |
$begingroup$
Q2 "It completely depends on the load the motor is given". Would that not be the nominal 200 amp rating? Assuming it is, would it then be drawing the RMS of the PWM wave? Also, you are likely correct that I have a low quality product, thanks for raising this point.
$endgroup$
– twegner
Apr 26 at 16:50
$begingroup$
Both the question and to some degree this attempted answer are making the fundamental mistake of assuming that the rating is a current draw. It is not, rather it is a "rating" (likely overly optimistic) of what the FETs on the ESC can handle. This has nothing to do with what the circuit may draw, which might be far less in proper operation, or substantially more in misapplication, leading to failure of whatever part of the installation is weakest (hopefully a user-provided fuse).
$endgroup$
– Chris Stratton
Apr 26 at 17:20
$begingroup$
@twegner: What I'm saying is that the load on the motor (bike going up a hill, winch lifting a load, etc.) determines the current requirement. If there is a light load then the current will be reduced. The maximum load that you can drive will be determined by the motor limit or ESC limit - whichever is the lower.
$endgroup$
– Transistor
Apr 26 at 18:00
$begingroup$
@Transistor: Yes, I understand. I should have phrased that as Max Throttle and full load - like heavy acceleration against a high resistance. So in this case, I assume the 200 amp nominal rating is what is being output (if that - according to Chris Stratton) from the ESC to the motor.
$endgroup$
– twegner
Apr 26 at 18:50
$begingroup$
@ChrisStratton: I didn't mean to imply the ESC rating is current draw. Rather I was questioning if the ESC's 200 amp output is what I should expect to be pulled from the battery pack or if it was more along the lines of the RMS of the output that would be pulled from the battery. Thanks for you input. Again, I was just looking for some high level theory, so this helps.
$endgroup$
– twegner
Apr 26 at 18:56
$begingroup$
Q2 "It completely depends on the load the motor is given". Would that not be the nominal 200 amp rating? Assuming it is, would it then be drawing the RMS of the PWM wave? Also, you are likely correct that I have a low quality product, thanks for raising this point.
$endgroup$
– twegner
Apr 26 at 16:50
$begingroup$
Q2 "It completely depends on the load the motor is given". Would that not be the nominal 200 amp rating? Assuming it is, would it then be drawing the RMS of the PWM wave? Also, you are likely correct that I have a low quality product, thanks for raising this point.
$endgroup$
– twegner
Apr 26 at 16:50
$begingroup$
Both the question and to some degree this attempted answer are making the fundamental mistake of assuming that the rating is a current draw. It is not, rather it is a "rating" (likely overly optimistic) of what the FETs on the ESC can handle. This has nothing to do with what the circuit may draw, which might be far less in proper operation, or substantially more in misapplication, leading to failure of whatever part of the installation is weakest (hopefully a user-provided fuse).
$endgroup$
– Chris Stratton
Apr 26 at 17:20
$begingroup$
Both the question and to some degree this attempted answer are making the fundamental mistake of assuming that the rating is a current draw. It is not, rather it is a "rating" (likely overly optimistic) of what the FETs on the ESC can handle. This has nothing to do with what the circuit may draw, which might be far less in proper operation, or substantially more in misapplication, leading to failure of whatever part of the installation is weakest (hopefully a user-provided fuse).
$endgroup$
– Chris Stratton
Apr 26 at 17:20
$begingroup$
@twegner: What I'm saying is that the load on the motor (bike going up a hill, winch lifting a load, etc.) determines the current requirement. If there is a light load then the current will be reduced. The maximum load that you can drive will be determined by the motor limit or ESC limit - whichever is the lower.
$endgroup$
– Transistor
Apr 26 at 18:00
$begingroup$
@twegner: What I'm saying is that the load on the motor (bike going up a hill, winch lifting a load, etc.) determines the current requirement. If there is a light load then the current will be reduced. The maximum load that you can drive will be determined by the motor limit or ESC limit - whichever is the lower.
$endgroup$
– Transistor
Apr 26 at 18:00
$begingroup$
@Transistor: Yes, I understand. I should have phrased that as Max Throttle and full load - like heavy acceleration against a high resistance. So in this case, I assume the 200 amp nominal rating is what is being output (if that - according to Chris Stratton) from the ESC to the motor.
$endgroup$
– twegner
Apr 26 at 18:50
$begingroup$
@Transistor: Yes, I understand. I should have phrased that as Max Throttle and full load - like heavy acceleration against a high resistance. So in this case, I assume the 200 amp nominal rating is what is being output (if that - according to Chris Stratton) from the ESC to the motor.
$endgroup$
– twegner
Apr 26 at 18:50
$begingroup$
@ChrisStratton: I didn't mean to imply the ESC rating is current draw. Rather I was questioning if the ESC's 200 amp output is what I should expect to be pulled from the battery pack or if it was more along the lines of the RMS of the output that would be pulled from the battery. Thanks for you input. Again, I was just looking for some high level theory, so this helps.
$endgroup$
– twegner
Apr 26 at 18:56
$begingroup$
@ChrisStratton: I didn't mean to imply the ESC rating is current draw. Rather I was questioning if the ESC's 200 amp output is what I should expect to be pulled from the battery pack or if it was more along the lines of the RMS of the output that would be pulled from the battery. Thanks for you input. Again, I was just looking for some high level theory, so this helps.
$endgroup$
– twegner
Apr 26 at 18:56
add a comment |
$begingroup$
All answers assume you're talking about "hobby" ESCs, as used in planes, boats, cars, robots, etc.
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps?
No. For the most part, the ESC draws what it draws given the motor, battery and load on the motor.
Some of the better ESC's do have current limiting, but experience in the flying field is that if you dork the thing into the dirt at full throttle, chances are that you'll damage the electronics due to overcurrent.
An ESC could be designed to limit current in such a way (I've designed industrial motor controllers that do), but AFAIK ESC's don't.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
See answer to question 1.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage?
Neither. At the level of the throttle command to motor, it supplies a fixed PWM to the motor -- essentially it chops the battery voltage and hands it to the motor.
This is complicated by the fact that some ESC's have a governor function, that servos the motor speed to the signal coming in -- but they still have an internal throttle command that works as above.
answered Apr 26 at 16:52
TimWescottTimWescott
7,5391417
$endgroup$
$begingroup$
Your Q3 response. I'm trying to understand this better. Are you saying the current is fixed and that the PWM is just shortened? (Like Transistors PWM graph) Basically the duty cycle is reduced but the current is not, but essentially this means less power is used.
$endgroup$
– twegner
Apr 26 at 19:08
$begingroup$
The PWM duty cycle is fixed by the "throttle" command. Cheaper ESCs don't even have a current sensor (other than the current-to-smoke converters that come free with every power electronics device in the world).
$endgroup$
– TimWescott
Apr 26 at 22:12
add a comment |
$begingroup$
All answers assume you're talking about "hobby" ESCs, as used in planes, boats, cars, robots, etc.
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps?
No. For the most part, the ESC draws what it draws given the motor, battery and load on the motor.
Some of the better ESC's do have current limiting, but experience in the flying field is that if you dork the thing into the dirt at full throttle, chances are that you'll damage the electronics due to overcurrent.
An ESC could be designed to limit current in such a way (I've designed industrial motor controllers that do), but AFAIK ESC's don't.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
See answer to question 1.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage?
Neither. At the level of the throttle command to motor, it supplies a fixed PWM to the motor -- essentially it chops the battery voltage and hands it to the motor.
This is complicated by the fact that some ESC's have a governor function, that servos the motor speed to the signal coming in -- but they still have an internal throttle command that works as above.
answered Apr 26 at 16:52
TimWescottTimWescott
7,5391417
$endgroup$
$begingroup$
Your Q3 response. I'm trying to understand this better. Are you saying the current is fixed and that the PWM is just shortened? (Like Transistors PWM graph) Basically the duty cycle is reduced but the current is not, but essentially this means less power is used.
$endgroup$
– twegner
Apr 26 at 19:08
$begingroup$
The PWM duty cycle is fixed by the "throttle" command. Cheaper ESCs don't even have a current sensor (other than the current-to-smoke converters that come free with every power electronics device in the world).
$endgroup$
– TimWescott
Apr 26 at 22:12
add a comment |
$begingroup$
All answers assume you're talking about "hobby" ESCs, as used in planes, boats, cars, robots, etc.
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps?
No. For the most part, the ESC draws what it draws given the motor, battery and load on the motor.
Some of the better ESC's do have current limiting, but experience in the flying field is that if you dork the thing into the dirt at full throttle, chances are that you'll damage the electronics due to overcurrent.
An ESC could be designed to limit current in such a way (I've designed industrial motor controllers that do), but AFAIK ESC's don't.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
See answer to question 1.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage?
Neither. At the level of the throttle command to motor, it supplies a fixed PWM to the motor -- essentially it chops the battery voltage and hands it to the motor.
This is complicated by the fact that some ESC's have a governor function, that servos the motor speed to the signal coming in -- but they still have an internal throttle command that works as above.
answered Apr 26 at 16:52
TimWescottTimWescott
7,5391417
$endgroup$
All answers assume you're talking about "hobby" ESCs, as used in planes, boats, cars, robots, etc.
Question 1: When an ESC is rated at 200 amps nominal and 500 amps peak is it safe to assume that the draw on the battery pack will not exceed 200 amps?
No. For the most part, the ESC draws what it draws given the motor, battery and load on the motor.
Some of the better ESC's do have current limiting, but experience in the flying field is that if you dork the thing into the dirt at full throttle, chances are that you'll damage the electronics due to overcurrent.
An ESC could be designed to limit current in such a way (I've designed industrial motor controllers that do), but AFAIK ESC's don't.
Question 2: If the motor is run indefinitely at max throttle (theoretically) will the ESC draw 200 amps from the battery continuously or less than that?
See answer to question 1.
Question 3: (slightly off topic) To modulate motor speed does the ESC restrict current flow or voltage?
Neither. At the level of the throttle command to motor, it supplies a fixed PWM to the motor -- essentially it chops the battery voltage and hands it to the motor.
This is complicated by the fact that some ESC's have a governor function, that servos the motor speed to the signal coming in -- but they still have an internal throttle command that works as above.
answered Apr 26 at 16:52
TimWescottTimWescott
7,5391417
answered Apr 26 at 16:52
TimWescottTimWescott
7,5391417
answered Apr 26 at 16:52
TimWescottTimWescott
7,5391417
answered Apr 26 at 16:52
TimWescottTimWescott
7,5391417
7,5391417
$begingroup$
Your Q3 response. I'm trying to understand this better. Are you saying the current is fixed and that the PWM is just shortened? (Like Transistors PWM graph) Basically the duty cycle is reduced but the current is not, but essentially this means less power is used.
$endgroup$
– twegner
Apr 26 at 19:08
$begingroup$
The PWM duty cycle is fixed by the "throttle" command. Cheaper ESCs don't even have a current sensor (other than the current-to-smoke converters that come free with every power electronics device in the world).
$endgroup$
– TimWescott
Apr 26 at 22:12
add a comment |
$begingroup$
Your Q3 response. I'm trying to understand this better. Are you saying the current is fixed and that the PWM is just shortened? (Like Transistors PWM graph) Basically the duty cycle is reduced but the current is not, but essentially this means less power is used.
$endgroup$
– twegner
Apr 26 at 19:08
$begingroup$
The PWM duty cycle is fixed by the "throttle" command. Cheaper ESCs don't even have a current sensor (other than the current-to-smoke converters that come free with every power electronics device in the world).
$endgroup$
– TimWescott
Apr 26 at 22:12
$begingroup$
Your Q3 response. I'm trying to understand this better. Are you saying the current is fixed and that the PWM is just shortened? (Like Transistors PWM graph) Basically the duty cycle is reduced but the current is not, but essentially this means less power is used.
$endgroup$
– twegner
Apr 26 at 19:08
$begingroup$
Your Q3 response. I'm trying to understand this better. Are you saying the current is fixed and that the PWM is just shortened? (Like Transistors PWM graph) Basically the duty cycle is reduced but the current is not, but essentially this means less power is used.
$endgroup$
– twegner
Apr 26 at 19:08
$begingroup$
The PWM duty cycle is fixed by the "throttle" command. Cheaper ESCs don't even have a current sensor (other than the current-to-smoke converters that come free with every power electronics device in the world).
$endgroup$
– TimWescott
Apr 26 at 22:12
$begingroup$
The PWM duty cycle is fixed by the "throttle" command. Cheaper ESCs don't even have a current sensor (other than the current-to-smoke converters that come free with every power electronics device in the world).
$endgroup$
– TimWescott
Apr 26 at 22:12
add a comment |
$begingroup$
The max operating temperature or heat rise above 25'C is what limits the nominal continuous current rating. The peak is an absolute maximum which may or may not be protected and should never be exceeded, such as starting a couple of these motors below at full throttle.
One must mind the rated peak currents to prevent damage to the electronics.
Similarily, a motor full load current rating is defined by the same method of temperature rise above 25'C for the winding hot spots. However every market does not use the same hot spot temperature for a long useful life and if no standards are given or not temp rise is specified, you might guess they don't want you to know.
However it is quite common to give the peak motor current as surge, start or locked rotor current. These are all the same as is simply Ohm's Law applied to the DC resistance or DCR, so Imax= V/DCR. This is typically Imax = 8 to 12 times the rated current in modern BLDC, high-efficiency DC motors.
Here they generously rate the motor current with a 180 second limit. This would be at max internal temperature.
answered Apr 26 at 18:49
Sunnyskyguy EE75Sunnyskyguy EE75
72.9k228103
$endgroup$
$begingroup$
If I'm reading the Tech sheet right, they are doing P=IV, so 885.4 watts = 4.2 vdc (not 3.7) * 4 cells * 52.7 amps. I understand your locked rotor 360 amp (V/R=I) calculation. So are you saying that as soon as the rotor locks, like if the parking brake was on (just go with it), that this motor should be paired with an ESC that can handle at least 360 amps? Which is way more than the Max Current on the spec sheet indicates. Also, thanks for providing a real world example. Yours and all the other answers are beginning to clear up my muddy understanding of this.
$endgroup$
– twegner
Apr 26 at 19:34
$begingroup$
The 885W is the motor power doing work if the batteries did not drop from a full charge at 4.2V for 120s, which seems unlikely even if they were 8P4S arrays as I believe it would drop to 3.6V at this current @ 120s. The 113 watts I calculated is DCR loss that makes the inefficiency 12.8% = 113/885W that produces heat while accelerating or braking until speed induced BEMF reduces the net voltage across the winding. So the ESC must use current feedback to regulate constant current to match this motor spec. limit. I expect ESC current-mode feedback limits torque and voltage regulates speed.
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:43
$begingroup$
I would expect an ESC of this caliber to have current limit control and voltage control. But I can't say for sure. AWG8= 2 mohm/m or 4mOhm/m pair
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:45
add a comment |
$begingroup$
The max operating temperature or heat rise above 25'C is what limits the nominal continuous current rating. The peak is an absolute maximum which may or may not be protected and should never be exceeded, such as starting a couple of these motors below at full throttle.
One must mind the rated peak currents to prevent damage to the electronics.
Similarily, a motor full load current rating is defined by the same method of temperature rise above 25'C for the winding hot spots. However every market does not use the same hot spot temperature for a long useful life and if no standards are given or not temp rise is specified, you might guess they don't want you to know.
However it is quite common to give the peak motor current as surge, start or locked rotor current. These are all the same as is simply Ohm's Law applied to the DC resistance or DCR, so Imax= V/DCR. This is typically Imax = 8 to 12 times the rated current in modern BLDC, high-efficiency DC motors.
Here they generously rate the motor current with a 180 second limit. This would be at max internal temperature.
answered Apr 26 at 18:49
Sunnyskyguy EE75Sunnyskyguy EE75
72.9k228103
$endgroup$
$begingroup$
If I'm reading the Tech sheet right, they are doing P=IV, so 885.4 watts = 4.2 vdc (not 3.7) * 4 cells * 52.7 amps. I understand your locked rotor 360 amp (V/R=I) calculation. So are you saying that as soon as the rotor locks, like if the parking brake was on (just go with it), that this motor should be paired with an ESC that can handle at least 360 amps? Which is way more than the Max Current on the spec sheet indicates. Also, thanks for providing a real world example. Yours and all the other answers are beginning to clear up my muddy understanding of this.
$endgroup$
– twegner
Apr 26 at 19:34
$begingroup$
The 885W is the motor power doing work if the batteries did not drop from a full charge at 4.2V for 120s, which seems unlikely even if they were 8P4S arrays as I believe it would drop to 3.6V at this current @ 120s. The 113 watts I calculated is DCR loss that makes the inefficiency 12.8% = 113/885W that produces heat while accelerating or braking until speed induced BEMF reduces the net voltage across the winding. So the ESC must use current feedback to regulate constant current to match this motor spec. limit. I expect ESC current-mode feedback limits torque and voltage regulates speed.
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:43
$begingroup$
I would expect an ESC of this caliber to have current limit control and voltage control. But I can't say for sure. AWG8= 2 mohm/m or 4mOhm/m pair
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:45
add a comment |
$begingroup$
The max operating temperature or heat rise above 25'C is what limits the nominal continuous current rating. The peak is an absolute maximum which may or may not be protected and should never be exceeded, such as starting a couple of these motors below at full throttle.
One must mind the rated peak currents to prevent damage to the electronics.
Similarily, a motor full load current rating is defined by the same method of temperature rise above 25'C for the winding hot spots. However every market does not use the same hot spot temperature for a long useful life and if no standards are given or not temp rise is specified, you might guess they don't want you to know.
However it is quite common to give the peak motor current as surge, start or locked rotor current. These are all the same as is simply Ohm's Law applied to the DC resistance or DCR, so Imax= V/DCR. This is typically Imax = 8 to 12 times the rated current in modern BLDC, high-efficiency DC motors.
Here they generously rate the motor current with a 180 second limit. This would be at max internal temperature.
answered Apr 26 at 18:49
Sunnyskyguy EE75Sunnyskyguy EE75
72.9k228103
$endgroup$
The max operating temperature or heat rise above 25'C is what limits the nominal continuous current rating. The peak is an absolute maximum which may or may not be protected and should never be exceeded, such as starting a couple of these motors below at full throttle.
One must mind the rated peak currents to prevent damage to the electronics.
Similarily, a motor full load current rating is defined by the same method of temperature rise above 25'C for the winding hot spots. However every market does not use the same hot spot temperature for a long useful life and if no standards are given or not temp rise is specified, you might guess they don't want you to know.
However it is quite common to give the peak motor current as surge, start or locked rotor current. These are all the same as is simply Ohm's Law applied to the DC resistance or DCR, so Imax= V/DCR. This is typically Imax = 8 to 12 times the rated current in modern BLDC, high-efficiency DC motors.
Here they generously rate the motor current with a 180 second limit. This would be at max internal temperature.
answered Apr 26 at 18:49
Sunnyskyguy EE75Sunnyskyguy EE75
72.9k228103
answered Apr 26 at 18:49
Sunnyskyguy EE75Sunnyskyguy EE75
72.9k228103
answered Apr 26 at 18:49
Sunnyskyguy EE75Sunnyskyguy EE75
72.9k228103
answered Apr 26 at 18:49
Sunnyskyguy EE75Sunnyskyguy EE75
72.9k228103
72.9k228103
$begingroup$
If I'm reading the Tech sheet right, they are doing P=IV, so 885.4 watts = 4.2 vdc (not 3.7) * 4 cells * 52.7 amps. I understand your locked rotor 360 amp (V/R=I) calculation. So are you saying that as soon as the rotor locks, like if the parking brake was on (just go with it), that this motor should be paired with an ESC that can handle at least 360 amps? Which is way more than the Max Current on the spec sheet indicates. Also, thanks for providing a real world example. Yours and all the other answers are beginning to clear up my muddy understanding of this.
$endgroup$
– twegner
Apr 26 at 19:34
$begingroup$
The 885W is the motor power doing work if the batteries did not drop from a full charge at 4.2V for 120s, which seems unlikely even if they were 8P4S arrays as I believe it would drop to 3.6V at this current @ 120s. The 113 watts I calculated is DCR loss that makes the inefficiency 12.8% = 113/885W that produces heat while accelerating or braking until speed induced BEMF reduces the net voltage across the winding. So the ESC must use current feedback to regulate constant current to match this motor spec. limit. I expect ESC current-mode feedback limits torque and voltage regulates speed.
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:43
$begingroup$
I would expect an ESC of this caliber to have current limit control and voltage control. But I can't say for sure. AWG8= 2 mohm/m or 4mOhm/m pair
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:45
add a comment |
$begingroup$
If I'm reading the Tech sheet right, they are doing P=IV, so 885.4 watts = 4.2 vdc (not 3.7) * 4 cells * 52.7 amps. I understand your locked rotor 360 amp (V/R=I) calculation. So are you saying that as soon as the rotor locks, like if the parking brake was on (just go with it), that this motor should be paired with an ESC that can handle at least 360 amps? Which is way more than the Max Current on the spec sheet indicates. Also, thanks for providing a real world example. Yours and all the other answers are beginning to clear up my muddy understanding of this.
$endgroup$
– twegner
Apr 26 at 19:34
$begingroup$
The 885W is the motor power doing work if the batteries did not drop from a full charge at 4.2V for 120s, which seems unlikely even if they were 8P4S arrays as I believe it would drop to 3.6V at this current @ 120s. The 113 watts I calculated is DCR loss that makes the inefficiency 12.8% = 113/885W that produces heat while accelerating or braking until speed induced BEMF reduces the net voltage across the winding. So the ESC must use current feedback to regulate constant current to match this motor spec. limit. I expect ESC current-mode feedback limits torque and voltage regulates speed.
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:43
$begingroup$
I would expect an ESC of this caliber to have current limit control and voltage control. But I can't say for sure. AWG8= 2 mohm/m or 4mOhm/m pair
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:45
$begingroup$
If I'm reading the Tech sheet right, they are doing P=IV, so 885.4 watts = 4.2 vdc (not 3.7) * 4 cells * 52.7 amps. I understand your locked rotor 360 amp (V/R=I) calculation. So are you saying that as soon as the rotor locks, like if the parking brake was on (just go with it), that this motor should be paired with an ESC that can handle at least 360 amps? Which is way more than the Max Current on the spec sheet indicates. Also, thanks for providing a real world example. Yours and all the other answers are beginning to clear up my muddy understanding of this.
$endgroup$
– twegner
Apr 26 at 19:34
$begingroup$
If I'm reading the Tech sheet right, they are doing P=IV, so 885.4 watts = 4.2 vdc (not 3.7) * 4 cells * 52.7 amps. I understand your locked rotor 360 amp (V/R=I) calculation. So are you saying that as soon as the rotor locks, like if the parking brake was on (just go with it), that this motor should be paired with an ESC that can handle at least 360 amps? Which is way more than the Max Current on the spec sheet indicates. Also, thanks for providing a real world example. Yours and all the other answers are beginning to clear up my muddy understanding of this.
$endgroup$
– twegner
Apr 26 at 19:34
$begingroup$
The 885W is the motor power doing work if the batteries did not drop from a full charge at 4.2V for 120s, which seems unlikely even if they were 8P4S arrays as I believe it would drop to 3.6V at this current @ 120s. The 113 watts I calculated is DCR loss that makes the inefficiency 12.8% = 113/885W that produces heat while accelerating or braking until speed induced BEMF reduces the net voltage across the winding. So the ESC must use current feedback to regulate constant current to match this motor spec. limit. I expect ESC current-mode feedback limits torque and voltage regulates speed.
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:43
$begingroup$
The 885W is the motor power doing work if the batteries did not drop from a full charge at 4.2V for 120s, which seems unlikely even if they were 8P4S arrays as I believe it would drop to 3.6V at this current @ 120s. The 113 watts I calculated is DCR loss that makes the inefficiency 12.8% = 113/885W that produces heat while accelerating or braking until speed induced BEMF reduces the net voltage across the winding. So the ESC must use current feedback to regulate constant current to match this motor spec. limit. I expect ESC current-mode feedback limits torque and voltage regulates speed.
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:43
$begingroup$
I would expect an ESC of this caliber to have current limit control and voltage control. But I can't say for sure. AWG8= 2 mohm/m or 4mOhm/m pair
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:45
$begingroup$
I would expect an ESC of this caliber to have current limit control and voltage control. But I can't say for sure. AWG8= 2 mohm/m or 4mOhm/m pair
$endgroup$
– Sunnyskyguy EE75
Apr 26 at 20:45
add a comment |
Thanks for contributing an answer to Electrical Engineering Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2felectronics.stackexchange.com%2fquestions%2f435606%2fbldc-motor-esc-and-battery-draw-nominal-vs-peak%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
$begingroup$
"When I see 200 amps I think of thick 2/0 awg gauge wire, not the 6 awg or 8 awg gauge wires I see on my ESC." - the 'silicone' insulation used on most ESC wires can handle higher temperature than PVC, so the current rating is higher, eg. 180A for 8AWG 4-max.co.uk/silicone-wire.htm
$endgroup$
– Bruce Abbott
Apr 27 at 0:50