Otdfbt

What is the difference between nullifying your vote and not going to vote at all?

Is it possible to kill all life on Earth?

Where can I find the list of all tendons in the human body?

How to prevent bad sectors?

Why does the UK have more political parties than the US?

When was the expression "Indian file" first used in English?

How did early x86 BIOS programmers manage to program full blown TUIs given very few bytes of ROM/EPROM?

Smart people send dumb people to a new planet on a space craft that crashes into a body of water

How to detach yourself from a character you're going to kill?

How to capture more stars?

Intuition behind eigenvalues of an adjacency matrix

Adding strings in lists together

Biblical Basis for 400 years of silence between old and new testament

How do I subvert the tropes of a train heist?

Lunar orbital rendezvous

My player wants to cast multiple charges of magic missile from a wand

Differences between “pas vrai ?”, “c’est ça ?”, “hein ?”, and “n’est-ce pas ?”

Is having a hidden directory under /etc safe?

How can I offer a test ride while selling a bike?

If a massive object like Jupiter flew past the Earth how close would it need to come to pull people off of the surface?

Draw a checker pattern with a black X in the center

Why would Lupin kill Pettigrew?

count number of files in directory with a certain name

Get LaTeX form from step by step solution

How can I safely determine the output voltage and current of a transformer?

MOT Power supply issuesBuilding a Tesla CoilMy first transformer causing safe fuse to go outMOT Power supply issuesCan multiple IGBTs share voltage?Is there any Phase difference between the current in primary and secondary coils of a transformer?Calculating the core area for a low frequency transformer part 2How can we measure the voltage at the coil of a Slayer Exciter?Tesla Coil Troubleshooting Help!High current low voltage transformer not workingCurrent input and output of transformer

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

1

1

$begingroup$

So I am building a Tesla coil with my partner for a senior design project.

We safely ripped out a transformer from a microwave oven. However, after a good amount of research, we were unable to find the maximum output values from the transformer. We know the input values, the standard 120 V and 60 Hz from a US outlet. We need to know the max/peak kV to figure out the capacitance we will need for our primary coil that we need to construct.

Here is what it looks like:

power-supply transformer high-voltage tesla-coil

share|improve this question

edited May 15 at 18:56

Greenonline

1,13931024

asked May 15 at 18:34

Krutik ShahKrutik Shah

93

$endgroup$

• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  $begingroup$
  We safely ripped out a transformer from a microwave oven Sure but the safety ends at the very moment when you connect the 120 V AC input to mains voltage when you want to use this transformer. Microwave transformers are designed to deliver a high voltage at significant current levels. Because that's the power going into the Magnetron tube. If you have to ask the rating of this transformer I seriously advise you to first get more experience with (high voltage) electronics before you continue.
  $endgroup$
  – Bimpelrekkie
  May 15 at 18:52
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  To be clear: without knowing exactly what you're doing you should not mess with the transformer from any microwave oven. They're LETHAL when connected to AC mains. Are you an electrical engineer? No, then leave these transformers alone. Even electrical engineers don't mess with these.
  $endgroup$
  – Bimpelrekkie
  May 15 at 18:57
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  well we were going to make a faraday cage and enclose the coil inside it before plugging in to the outlet. we can also just make a small-scale tesla coil without having to deal with these big transformers, a student from a previous year did it and we have been using it as a reference but we're not exactly sure how it is getting the job done with only the 120 V input thats connected straight to what looks like the primary winding.
  $endgroup$
  – Krutik Shah
  May 15 at 19:24
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Besides being extremely dangerous, IMO this is a poor senior design project, I am surprised that a professor would approve this. There is a lot of "black magic" involved, since the parasitics are difficult to estimate, you can't use always us rigorous engineering math. IMO a senior design project should involve requirements and math/simulations to back-up the design besides successful execution of the design. What are your requirements, lots of cool sparks?
  $endgroup$
  – Mattman944
  May 15 at 23:04
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Have a friend do the measurements for you.
  $endgroup$
  – copper.hat
  May 16 at 0:31
  

  
  
  
  

 | 
show 2 more comments

1

1

$begingroup$

So I am building a Tesla coil with my partner for a senior design project.

We safely ripped out a transformer from a microwave oven. However, after a good amount of research, we were unable to find the maximum output values from the transformer. We know the input values, the standard 120 V and 60 Hz from a US outlet. We need to know the max/peak kV to figure out the capacitance we will need for our primary coil that we need to construct.

Here is what it looks like:

power-supply transformer high-voltage tesla-coil

share|improve this question

edited May 15 at 18:56

Greenonline

1,13931024

asked May 15 at 18:34

Krutik ShahKrutik Shah

93

$endgroup$

• 
  
  
  

  
  6
  

  
  
  
  
  
  

  
  $begingroup$
  We safely ripped out a transformer from a microwave oven Sure but the safety ends at the very moment when you connect the 120 V AC input to mains voltage when you want to use this transformer. Microwave transformers are designed to deliver a high voltage at significant current levels. Because that's the power going into the Magnetron tube. If you have to ask the rating of this transformer I seriously advise you to first get more experience with (high voltage) electronics before you continue.
  $endgroup$
  – Bimpelrekkie
  May 15 at 18:52
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  To be clear: without knowing exactly what you're doing you should not mess with the transformer from any microwave oven. They're LETHAL when connected to AC mains. Are you an electrical engineer? No, then leave these transformers alone. Even electrical engineers don't mess with these.
  $endgroup$
  – Bimpelrekkie
  May 15 at 18:57
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  well we were going to make a faraday cage and enclose the coil inside it before plugging in to the outlet. we can also just make a small-scale tesla coil without having to deal with these big transformers, a student from a previous year did it and we have been using it as a reference but we're not exactly sure how it is getting the job done with only the 120 V input thats connected straight to what looks like the primary winding.
  $endgroup$
  – Krutik Shah
  May 15 at 19:24
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Besides being extremely dangerous, IMO this is a poor senior design project, I am surprised that a professor would approve this. There is a lot of "black magic" involved, since the parasitics are difficult to estimate, you can't use always us rigorous engineering math. IMO a senior design project should involve requirements and math/simulations to back-up the design besides successful execution of the design. What are your requirements, lots of cool sparks?
  $endgroup$
  – Mattman944
  May 15 at 23:04
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Have a friend do the measurements for you.
  $endgroup$
  – copper.hat
  May 16 at 0:31
  

  
  
  
  

 | 
show 2 more comments

$begingroup$

So I am building a Tesla coil with my partner for a senior design project.

We safely ripped out a transformer from a microwave oven. However, after a good amount of research, we were unable to find the maximum output values from the transformer. We know the input values, the standard 120 V and 60 Hz from a US outlet. We need to know the max/peak kV to figure out the capacitance we will need for our primary coil that we need to construct.

Here is what it looks like:

power-supply transformer high-voltage tesla-coil

share|improve this question

edited May 15 at 18:56

Greenonline

1,13931024

asked May 15 at 18:34

Krutik ShahKrutik Shah

93

$endgroup$

share|improve this question

edited May 15 at 18:56

Greenonline

1,13931024

asked May 15 at 18:34

Krutik ShahKrutik Shah

93

share|improve this question

edited May 15 at 18:56

Greenonline

1,13931024

asked May 15 at 18:34

Krutik ShahKrutik Shah

93

edited May 15 at 18:56

Greenonline

1,13931024

edited May 15 at 18:56

Greenonline

1,13931024

asked May 15 at 18:34

Krutik ShahKrutik Shah

93

asked May 15 at 18:34

Krutik ShahKrutik Shah

93

4 Answers
4

active

oldest

votes

8

$begingroup$

No. Do not use a Microwave Oven Transformer (MOT) for a Tesla coil.

It is the wrong impedance. The output voltage is too low (around 2kV), spark gaps will not fire reliably. The output current is too high (500mA), if it bites you, you will probably die.

The correct transformer to use is an old style (iron core) Neon Sign Transformer (NST). The output voltage of 15kV is plenty to make very forgiving spark gaps. The output current in the low tens of mA may well be survivable if it bites you.

share|improve this answer

answered May 15 at 18:57

Neil_UKNeil_UK

81k285188

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  For clarification, so a microwave transformer is not high enough voltage to easily make spark gaps, but at the same time high enough voltage to produce hazardous sparks and high enough power to have lethal levels of current behind those sparks?
  $endgroup$
  – DKNguyen
  May 15 at 19:00
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @Toor There's a lot of technology to Tesla Coils, technology = knowledge of how to make them work. 2kV will jump very short gaps in air. However, making a reliable gap that size with big copper electrodes to dissipate the heat is hard, it's not something experienced coilers attempt, somebody with no experience is doooomed to failure. It is enough to jump through dry clothing, mains will not do that, which is why mains is relatively safe, and MOTs are lethal. Once an arc has started, that 500mA will start fires (1kW!) and is 10x the level needed to stop a heart.
  $endgroup$
  – Neil_UK
  May 15 at 19:05
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  Toor, 2 kV with current capability of 500 mA will easily kill you, and not by "sparks". It's volts that jolt, but mils that kill.
  $endgroup$
  – Michael Harvey
  May 15 at 19:06
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @MichaelHarvey Isn't that what I said?
  $endgroup$
  – DKNguyen
  May 15 at 19:06
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @KrutikShah these are the games people get into when they try to make a MOT-powered TC, once you're up at 4 MOTs, the spark gaps become reasonable. The power level is totally unreasonable.
  $endgroup$
  – Neil_UK
  May 15 at 19:19
  

  
  
  
  

 | 
show 4 more comments

8

$begingroup$

6170W1D012G is an LG part number. Primary 120v. HT secondary is 2210v 500 mA. If you have to ask, as has been said, you do not know enough to do this safely.

share|improve this answer

edited May 15 at 20:29

answered May 15 at 18:59

Michael HarveyMichael Harvey

1965

$endgroup$

add a comment | 

1

$begingroup$

Consider exciting the high voltage secondary (at 60 Hz) and measuring primary voltage to get an idea of the turns ratio. It should be pretty simple math past that.

I agree with other comments that you might want more experience and/or meaningful oversight from your professors for this project.

share|improve this answer

edited May 15 at 18:54

answered May 15 at 18:53

MondayTuesdayWednesdayMondayTuesdayWednesday

112

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Sure but that does not tell us anything about the power rating of this transformer.
  $endgroup$
  – Bimpelrekkie
  May 15 at 18:54
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  What was the power rating of the microwave? You probably can't establish a rating without input from the manufacturer, nameplate information, or testing and knowledge of the construction (insulation temp ratings mostly).
  $endgroup$
  – MondayTuesdayWednesday
  May 15 at 18:55
  
  

  
  
  
  

add a comment | 

1

$begingroup$

To answer the general question, to suss out the basic specs of a power transformer drive it backwards. This is how we did it in engineering school with pole transformers.

You apply 120vac to the HV secondary of the transformer, then measure the voltage on the primary. (Note: Be sure to fuse the 120v supply.) This will let you calculate the ratio of primary to secondary voltage. There was also a way to roughly calculate the current capacity while doing this, but it's been nearly 50 years, so I've forgotten that detail.

share|improve this answer

answered May 15 at 22:03

Hot LicksHot Licks

62548

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Note: This is a microwave oven transformer. It has an HT secondary winding, and also a 3.15v secondary winding for the magnetron cathode heater filament. If attempting a backward measurement, then identifying the right secondary is important, as applying 120v to the 3.15v winding is likely to cause hazardous voltages to appear at the primary, and/or damage the transformer.
  $endgroup$
  – Michael Harvey
  May 16 at 9:24
  

  
  
  
  

add a comment | 

protected by W5VO♦ May 15 at 21:51

Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).



Would you like to answer one of these unanswered questions instead?

8

$begingroup$

No. Do not use a Microwave Oven Transformer (MOT) for a Tesla coil.

It is the wrong impedance. The output voltage is too low (around 2kV), spark gaps will not fire reliably. The output current is too high (500mA), if it bites you, you will probably die.

The correct transformer to use is an old style (iron core) Neon Sign Transformer (NST). The output voltage of 15kV is plenty to make very forgiving spark gaps. The output current in the low tens of mA may well be survivable if it bites you.

share|improve this answer

answered May 15 at 18:57

Neil_UKNeil_UK

81k285188

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  For clarification, so a microwave transformer is not high enough voltage to easily make spark gaps, but at the same time high enough voltage to produce hazardous sparks and high enough power to have lethal levels of current behind those sparks?
  $endgroup$
  – DKNguyen
  May 15 at 19:00
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @Toor There's a lot of technology to Tesla Coils, technology = knowledge of how to make them work. 2kV will jump very short gaps in air. However, making a reliable gap that size with big copper electrodes to dissipate the heat is hard, it's not something experienced coilers attempt, somebody with no experience is doooomed to failure. It is enough to jump through dry clothing, mains will not do that, which is why mains is relatively safe, and MOTs are lethal. Once an arc has started, that 500mA will start fires (1kW!) and is 10x the level needed to stop a heart.
  $endgroup$
  – Neil_UK
  May 15 at 19:05
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  Toor, 2 kV with current capability of 500 mA will easily kill you, and not by "sparks". It's volts that jolt, but mils that kill.
  $endgroup$
  – Michael Harvey
  May 15 at 19:06
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @MichaelHarvey Isn't that what I said?
  $endgroup$
  – DKNguyen
  May 15 at 19:06
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @KrutikShah these are the games people get into when they try to make a MOT-powered TC, once you're up at 4 MOTs, the spark gaps become reasonable. The power level is totally unreasonable.
  $endgroup$
  – Neil_UK
  May 15 at 19:19
  

  
  
  
  

 | 
show 4 more comments

8

$begingroup$

No. Do not use a Microwave Oven Transformer (MOT) for a Tesla coil.

It is the wrong impedance. The output voltage is too low (around 2kV), spark gaps will not fire reliably. The output current is too high (500mA), if it bites you, you will probably die.

The correct transformer to use is an old style (iron core) Neon Sign Transformer (NST). The output voltage of 15kV is plenty to make very forgiving spark gaps. The output current in the low tens of mA may well be survivable if it bites you.

share|improve this answer

answered May 15 at 18:57

Neil_UKNeil_UK

81k285188

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  For clarification, so a microwave transformer is not high enough voltage to easily make spark gaps, but at the same time high enough voltage to produce hazardous sparks and high enough power to have lethal levels of current behind those sparks?
  $endgroup$
  – DKNguyen
  May 15 at 19:00
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @Toor There's a lot of technology to Tesla Coils, technology = knowledge of how to make them work. 2kV will jump very short gaps in air. However, making a reliable gap that size with big copper electrodes to dissipate the heat is hard, it's not something experienced coilers attempt, somebody with no experience is doooomed to failure. It is enough to jump through dry clothing, mains will not do that, which is why mains is relatively safe, and MOTs are lethal. Once an arc has started, that 500mA will start fires (1kW!) and is 10x the level needed to stop a heart.
  $endgroup$
  – Neil_UK
  May 15 at 19:05
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  Toor, 2 kV with current capability of 500 mA will easily kill you, and not by "sparks". It's volts that jolt, but mils that kill.
  $endgroup$
  – Michael Harvey
  May 15 at 19:06
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @MichaelHarvey Isn't that what I said?
  $endgroup$
  – DKNguyen
  May 15 at 19:06
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @KrutikShah these are the games people get into when they try to make a MOT-powered TC, once you're up at 4 MOTs, the spark gaps become reasonable. The power level is totally unreasonable.
  $endgroup$
  – Neil_UK
  May 15 at 19:19
  

  
  
  
  

 | 
show 4 more comments

$begingroup$

No. Do not use a Microwave Oven Transformer (MOT) for a Tesla coil.

It is the wrong impedance. The output voltage is too low (around 2kV), spark gaps will not fire reliably. The output current is too high (500mA), if it bites you, you will probably die.

The correct transformer to use is an old style (iron core) Neon Sign Transformer (NST). The output voltage of 15kV is plenty to make very forgiving spark gaps. The output current in the low tens of mA may well be survivable if it bites you.

share|improve this answer

answered May 15 at 18:57

Neil_UKNeil_UK

81k285188

$endgroup$

share|improve this answer

answered May 15 at 18:57

Neil_UKNeil_UK

81k285188

answered May 15 at 18:57

Neil_UKNeil_UK

81k285188

answered May 15 at 18:57

Neil_UKNeil_UK

81k285188

8

$begingroup$

6170W1D012G is an LG part number. Primary 120v. HT secondary is 2210v 500 mA. If you have to ask, as has been said, you do not know enough to do this safely.

share|improve this answer

edited May 15 at 20:29

answered May 15 at 18:59

Michael HarveyMichael Harvey

1965

$endgroup$

add a comment | 

8

$begingroup$

6170W1D012G is an LG part number. Primary 120v. HT secondary is 2210v 500 mA. If you have to ask, as has been said, you do not know enough to do this safely.

share|improve this answer

edited May 15 at 20:29

answered May 15 at 18:59

Michael HarveyMichael Harvey

1965

$endgroup$

add a comment | 

$begingroup$

6170W1D012G is an LG part number. Primary 120v. HT secondary is 2210v 500 mA. If you have to ask, as has been said, you do not know enough to do this safely.

share|improve this answer

edited May 15 at 20:29

answered May 15 at 18:59

Michael HarveyMichael Harvey

1965

$endgroup$

share|improve this answer

edited May 15 at 20:29

answered May 15 at 18:59

Michael HarveyMichael Harvey

1965

answered May 15 at 18:59

Michael HarveyMichael Harvey

1965

answered May 15 at 18:59

Michael HarveyMichael Harvey

1965

1

$begingroup$

Consider exciting the high voltage secondary (at 60 Hz) and measuring primary voltage to get an idea of the turns ratio. It should be pretty simple math past that.

I agree with other comments that you might want more experience and/or meaningful oversight from your professors for this project.

share|improve this answer

edited May 15 at 18:54

answered May 15 at 18:53

MondayTuesdayWednesdayMondayTuesdayWednesday

112

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Sure but that does not tell us anything about the power rating of this transformer.
  $endgroup$
  – Bimpelrekkie
  May 15 at 18:54
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  What was the power rating of the microwave? You probably can't establish a rating without input from the manufacturer, nameplate information, or testing and knowledge of the construction (insulation temp ratings mostly).
  $endgroup$
  – MondayTuesdayWednesday
  May 15 at 18:55
  
  

  
  
  
  

add a comment | 

1

$begingroup$

Consider exciting the high voltage secondary (at 60 Hz) and measuring primary voltage to get an idea of the turns ratio. It should be pretty simple math past that.

I agree with other comments that you might want more experience and/or meaningful oversight from your professors for this project.

share|improve this answer

edited May 15 at 18:54

answered May 15 at 18:53

MondayTuesdayWednesdayMondayTuesdayWednesday

112

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Sure but that does not tell us anything about the power rating of this transformer.
  $endgroup$
  – Bimpelrekkie
  May 15 at 18:54
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  What was the power rating of the microwave? You probably can't establish a rating without input from the manufacturer, nameplate information, or testing and knowledge of the construction (insulation temp ratings mostly).
  $endgroup$
  – MondayTuesdayWednesday
  May 15 at 18:55
  
  

  
  
  
  

add a comment | 

$begingroup$

Consider exciting the high voltage secondary (at 60 Hz) and measuring primary voltage to get an idea of the turns ratio. It should be pretty simple math past that.

I agree with other comments that you might want more experience and/or meaningful oversight from your professors for this project.

share|improve this answer

edited May 15 at 18:54

answered May 15 at 18:53

MondayTuesdayWednesdayMondayTuesdayWednesday

112

$endgroup$

share|improve this answer

edited May 15 at 18:54

answered May 15 at 18:53

MondayTuesdayWednesdayMondayTuesdayWednesday

112

answered May 15 at 18:53

MondayTuesdayWednesdayMondayTuesdayWednesday

112

answered May 15 at 18:53

MondayTuesdayWednesdayMondayTuesdayWednesday

112

1

$begingroup$

To answer the general question, to suss out the basic specs of a power transformer drive it backwards. This is how we did it in engineering school with pole transformers.

You apply 120vac to the HV secondary of the transformer, then measure the voltage on the primary. (Note: Be sure to fuse the 120v supply.) This will let you calculate the ratio of primary to secondary voltage. There was also a way to roughly calculate the current capacity while doing this, but it's been nearly 50 years, so I've forgotten that detail.

share|improve this answer

answered May 15 at 22:03

Hot LicksHot Licks

62548

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Note: This is a microwave oven transformer. It has an HT secondary winding, and also a 3.15v secondary winding for the magnetron cathode heater filament. If attempting a backward measurement, then identifying the right secondary is important, as applying 120v to the 3.15v winding is likely to cause hazardous voltages to appear at the primary, and/or damage the transformer.
  $endgroup$
  – Michael Harvey
  May 16 at 9:24
  

  
  
  
  

add a comment | 

1

$begingroup$

To answer the general question, to suss out the basic specs of a power transformer drive it backwards. This is how we did it in engineering school with pole transformers.

You apply 120vac to the HV secondary of the transformer, then measure the voltage on the primary. (Note: Be sure to fuse the 120v supply.) This will let you calculate the ratio of primary to secondary voltage. There was also a way to roughly calculate the current capacity while doing this, but it's been nearly 50 years, so I've forgotten that detail.

share|improve this answer

answered May 15 at 22:03

Hot LicksHot Licks

62548

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Note: This is a microwave oven transformer. It has an HT secondary winding, and also a 3.15v secondary winding for the magnetron cathode heater filament. If attempting a backward measurement, then identifying the right secondary is important, as applying 120v to the 3.15v winding is likely to cause hazardous voltages to appear at the primary, and/or damage the transformer.
  $endgroup$
  – Michael Harvey
  May 16 at 9:24
  

  
  
  
  

add a comment | 

$begingroup$

To answer the general question, to suss out the basic specs of a power transformer drive it backwards. This is how we did it in engineering school with pole transformers.

You apply 120vac to the HV secondary of the transformer, then measure the voltage on the primary. (Note: Be sure to fuse the 120v supply.) This will let you calculate the ratio of primary to secondary voltage. There was also a way to roughly calculate the current capacity while doing this, but it's been nearly 50 years, so I've forgotten that detail.

share|improve this answer

answered May 15 at 22:03

Hot LicksHot Licks

62548

$endgroup$

share|improve this answer

answered May 15 at 22:03

Hot LicksHot Licks

62548

answered May 15 at 22:03

Hot LicksHot Licks

62548

answered May 15 at 22:03

Hot LicksHot Licks

62548