High Voltage Check
 

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 .

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

Courtesy of Sam.

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

"ri" wrote in message
...
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?

"ri" wrote in message
...
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.

"ri" wrote in message
...
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

"NSM" wrote in message
news:nK7Zd.56187$fc4.41712@edtnps89...

"ri" wrote in message
...
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

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.

"ri" wrote in message
...
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.
--
John G

Wot's Your Real Problem?

"Terry" wrote in message
.. .

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

NSM wrote:

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

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 .

John G wrote:

"ri" wrote in message
...
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.
--
John G

Wot's Your Real Problem?

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

James Sweet wrote:

"ri" wrote in message
...
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" writes:

"Terry" wrote in message
.. .

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.

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.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

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.

NSM wrote:

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!

--
?

Michael A. Terrell
Central Florida

Can you read ?


"ri" wrote in message
...
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 .

John G wrote:

"ri" wrote in message
...
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.
--
John G

Wot's Your Real Problem?

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

kip wrote:

Can you read ?

"ri" wrote in message
...
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 .

John G wrote:

"ri" wrote in message
...
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.
--
John G

Wot's Your Real Problem?

"Michael A. Terrell" wrote in message
...
NSM wrote:

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!

Or tube equipped military transmitters!

N

"Sam Goldwasser" wrote in message
...

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

"ri" wrote in message
...
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

ri wrote:
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.

ri wrote:
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

Matthew Smith writes:

ri wrote:
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.

Which are extremely high in a microwave oven transformer.

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

Yeah, how many have that?

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.

That sounds like the hard way. :)

Just run it with 1/10th the input voltage as has already been suggested.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

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.

TYPO
Since you need to ask, you do NOT know enough to undertake this type
of repair as it could very quickly lead to your family having to call
the
Undertaker.

"John G" wrote in message
...

"ri" wrote in message
...
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 NOT know enough to undertake this type
of repair as it could very quickly lead to your family having to call
the Undertaker.
--
John G

Wot's Your Real Problem?

On Mon, 14 Mar 2005 20:22:28 GMT, NSM wrote:

"ri" wrote in message
...
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.

Brings back memories of testing the H.V. used on the magnetron in the radar
system of the USAF F-102 on the mock-up bench at Ramstein AB
back in the early to mid-60's. I would clip several USM-6's in series
and spread them apart on a large piece of plywood. Then I'd clip them
onto the H.V. points in the T/R unit and power up the thing. I'd
stand back about 2-3 feet and read each meter -- then add the values
together. It was probably just plain dumb luck that I recieved
an _honorable_ discharge instead of receiving some sort of _other_ discharge.

Jonesy
--
| Marvin L Jones | jonz | W3DHJ | linux
| Gunnison, Colorado | @ | Jonesy | OS/2 __
| 7,703' -- 2,345m | config.com | DM68mn SK

Thanks everyone who answered to this subject :
Problem is solved and one on the transformers is perfect for my purpose . Thanks
again to all .

Sam Goldwasser wrote:

Matthew Smith writes:

ri wrote:
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.

Which are extremely high in a microwave oven transformer.

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

Yeah, how many have that?

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.

That sounds like the hard way. :)

Just run it with 1/10th the input voltage as has already been suggested.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

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.

"ri" wrote in message
...
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 .


Several have already answered your question... feed the transformer a lower
AC voltage and measure the correspondingly lower output.

"NSM" wrote in message
news:DemZd.36561$ZO2.15936@edtnps84...

"Sam Goldwasser" wrote in message
...

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.


I got bit by a NST once, it did NOT feel good, however my finger wasn't
reduced to ash as it could have been by a microwave transformer. Both are
dangerous but the as others have said, the current from a NST is much lower.

Yeah James , thanks . That is what I did and 1 of the microwave transformers
will be perfect for my plate voltage supply . Thanks James and all who gave a
good answer to my question . Thanks again

James Sweet wrote:

"ri" wrote in message
...
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 .

Several have already answered your question... feed the transformer a lower
AC voltage and measure the correspondingly lower output.

"ri" wrote in message
...
Hey kip , screw off . I work with electricity almost everyday . I know
what
it can do. Screw off

That'll get you a lot of help. You come off like someone who knows nothing.
Expect to be treated as such. almost everyday. And you don't know what
electricity can do until you lose your hearing and you are sick to your
stomach for 15 minutes. There are old electricians and there are bold
electricians but there there are no old, bold electricians

N