High Voltage Check

[ri]

Hi Group , I have a microwave transformer I need to check the output
voltage on .
I'm sure the voltage will exceed my multi-meter range . The voltage will
exceed 1000 volts . What is the best way to check a transformer of this
type ?
Thanks to all in this group for all responses in advance .

 

[Travis Jordan]

Hi Group , I have a microwave transformer I need to check the output

Courtesy of Sam.

http://repairfaq.ece.drexel.edu/sam/hvprobe.htm

 

[Charles Schuler]

Hi Group , I have a microwave transformer I need to check the output
voltage on .
I'm sure the voltage will exceed my multi-meter range .

Get another meter?

 

[James Sweet]

Hi Group , I have a microwave transformer I need to check the output
voltage on .
I'm sure the voltage will exceed my multi-meter range . The voltage will
exceed 1000 volts . What is the best way to check a transformer of this
type ?
Thanks to all in this group for all responses in advance .

Connect the primary to a 12vac source such as a garden lighting transformer,
the secondary should then read about 1/10th it's rated voltage.

 

[NSM]

Hi Group , I have a microwave transformer I need to check the output
voltage on .
I'm sure the voltage will exceed my multi-meter range . The voltage will
exceed 1000 volts . What is the best way to check a transformer of this
type ?
Thanks to all in this group for all responses in advance .

Is your insurance paid up? Does your wife know how to cut off the power and
do CPR?

N

 

[Terry]

Is your insurance paid up? Does your wife know how to cut off the power
and
do CPR?

N

Agree:
Be careful not only of the AC voltage on the secondary of that transformer
but the voltage doubling DC circuit which can more than adequately kill you!
Not only that; if you operate with the cover off stand clear of possible
microwave radiation!
After all they are a half kilowatt microwave transmitter in a tin box!
I will venture a guess that if the transformer (with the power off and
unplugged) tests continuity and doesn't look burnt up, it is not faulty.
More likely another component, all operating at very (repeat very) high
voltage.

 

[John G]

Hi Group , I have a microwave transformer I need to check the output
voltage on .
I'm sure the voltage will exceed my multi-meter range . The voltage
will
exceed 1000 volts . What is the best way to check a transformer of
this
type ?
Thanks to all in this group for all responses in advance .

Since you need to ask, you do know enough to undertake this type of
repair as it could very quickly lead to your family having to call the
Undertaker.

 

[NSM]

Agree:
Be careful not only of the AC voltage on the secondary of that transformer
but the voltage doubling DC circuit which can more than adequately kill you!
Not only that; if you operate with the cover off stand clear of possible
microwave radiation!
After all they are a half kilowatt microwave transmitter in a tin box!
I will venture a guess that if the transformer (with the power off and
unplugged) tests continuity and doesn't look burnt up, it is not faulty.
More likely another component, all operating at very (repeat very) high
voltage.

Yep. This is a classic case of stand on dry newspaper, use one hand only,
clip the leads to the machine and then cycle AC power at the wall for the
test. One flash and you're ash. There aren't many items more hazardous to
service - except maybe neon signs.

N

 

[Matthew Smith]

Yep. This is a classic case of stand on dry newspaper, use one hand only,
clip the leads to the machine and then cycle AC power at the wall for the
test. One flash and you're ash. There aren't many items more hazardous to
service - except maybe neon signs.

Possibly worse than neon signs. Neon sign transformers tend to have a
higher output voltage than microwave oven transformers but are current
limited. Whilst microwave oven transformers have magnetic shunts
(current limiting through core saturation), they're still capable of
chucking out an Amp or so. A couple of kilowatts going through you could
ruin your day.

I do it the "sissy" way and feed 'em through a Variac - one fried DMM
has shown me that it's not only personal safety that's at stake.

"Toil not thou on energized equipment, for if thou so dost, thy fellow
workers will surely buy beers for thy widow and console her otherwise."

M

 

[ri]

Hi Group , all I am working with here is the High Voltage Transformer
itself . The rest of the microwave oven has been discarded as trash . I
need a transformer that has an output of 1,500 volts for use as a plate
transformer . I have several microwave transformers to test .
This brings me back to the question of testing the voltage . How is the
best way to check the voltage ? Thanks again .

 

[ri]

Thanks James , that sounds like a good way to check the transformer . I will try
it your way . Thanks

 

[Sam Goldwasser]

Yep. This is a classic case of stand on dry newspaper, use one hand only,
clip the leads to the machine and then cycle AC power at the wall for the
test. One flash and you're ash. There aren't many items more hazardous to
service - except maybe neon signs.

Neon signs are trivial in comparison.

The different between 20 or 30 mA and 0.5 to 1 AMP.

Neon sign transformers are current limited.

Still near the threshold of lethality but microwave transformers are
way over it.

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Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

 

[Michael A. Terrell]

Yep. This is a classic case of stand on dry newspaper, use one hand only,
clip the leads to the machine and then cycle AC power at the wall for the
test. One flash and you're ash. There aren't many items more hazardous to
service - except maybe neon signs.

N

Stay out of TV transmitters!

 

[kip]

Can you read ?

Hi Group , all I am working with here is the High Voltage Transformer
itself . The rest of the microwave oven has been discarded as trash . I
need a transformer that has an output of 1,500 volts for use as a plate
transformer . I have several microwave transformers to test .
This brings me back to the question of testing the voltage . How is the
best way to check the voltage ? Thanks again .

 

[ri]

Hey kip , screw off . I work with electricity almost everyday . I know what
it can do. Screw off

Can you read ?

 

[NSM]

Stay out of TV transmitters!

Or tube equipped military transmitters!

N

 

[NSM]

Neon signs are trivial in comparison.

The different between 20 or 30 mA and 0.5 to 1 AMP.

Neon sign transformers are current limited.

30 mA will ruin your day hand to hand.

N

 

[NSM]

Hi Group , all I am working with here is the High Voltage Transformer
itself . The rest of the microwave oven has been discarded as trash . I
need a transformer that has an output of 1,500 volts for use as a plate
transformer . I have several microwave transformers to test .
This brings me back to the question of testing the voltage . How is the
best way to check the voltage?

Very, very, very, very, very, very, very, very, very, very, very, very
carefully.

Don't even THINK of touching any part of the multimeter while testing.

N

 

[Travis Jordan]

This brings me back to the question of testing the voltage . How is
the best way to check the voltage ? Thanks again .

Build a high voltage probe.

 

[Matthew Smith]

Hi Group , all I am working with here is the High Voltage Transformer
itself . The rest of the microwave oven has been discarded as trash . I
need a transformer that has an output of 1,500 volts for use as a plate
transformer . I have several microwave transformers to test .
This brings me back to the question of testing the voltage . How is the
best way to check the voltage ? Thanks again .

There is a relatively safe way to calculate the secondary voltage - no
mains energisation required; it's just not too accurate as it takes no
account of losses.

Got a DMM with a decent inductance range? You can get a ballpark value
thus:

Zp=sqrt( (Rp^2) + (2 * PI * f * Lp)^2 );
Zs=sqrt( (Rs^2) + (2 * PI * f * Ls)^2 );
np/ns=sqrt(Zp/Zs);
Vp/Vs=np/ns;

Where f is your local line frequency.


M