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PS Current Test?


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From:  Thomas McGahee [SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent:  Sunday, March 22, 1998 9:01 AM
To:  Tesla List
Cc:  andrus-at-ccountry-dot-net
Subject:  Re: PS Current Test?



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> From: Tesla List <tesla-at-stic-dot-net>
> To: 'Thomas McGahee' <tom_mcgahee-at-sigmais-dot-com>
> Subject: PS Current Test?
> Date: Saturday, March 21, 1998 3:46 PM
> 
> 
> 
> ----------
> From:  Michael Andrus [SMTP:andrus-at-ccountry-dot-net]
> Sent:  Saturday, March 21, 1998 10:30 AM
> To:  tesla-at-pupman-dot-com
> Subject:  PS Current Test?
> 
> Does anyone know how to determin the current rating on an unmarked 6kv gas
heat ignition xfmr?                            >Michael Andrus

Michael,
Since the transformer is current limited there is an easy method.
Either connect an AC milliameter set on the 100 ma scale
directly across the HV electrodes (make sure you insulate it),
--or-- 
Put a 1K ohm 1 watt resistor across the HV electrodes and
measure the AC voltage across the resistor. Every volt will
represent 1 milliamp.  Typically oil burner transformers
range between 10 and 45 ma.

This method will --only-- work with current limited transformers.
It is safe as long as you keep the meter isolated during the
measurement.

Connect the AC meter or AC meter/resistor up and then apply 
power to the primary as usual. Try to keep the measurement
period to ten seconds or less. Note that 30 ma will cause
30 volts across the 1K resistor, resulting in .9 watts of
power being dissipated by the resistor. 1 Watt is the
minimum size power rating you should use. As the resistor
heats up the reading may change due to the change in actual
resistance. For this reason either keep the test run as 
short as possible, or use a higher power resitor, such as
a 5 watt unit. 

You can also use a 100 ohm resistor. In 
that case every volt across it represents 10 ma going 
through it. With the 100 ohm resistor 30 ma would only
cause .09 watts of power to be dissipated by the resistor.

Use whatever you can get your hands on most readily.
The method is quite safe both for you and your meter, so
long as you keep the meter isolated during the actual test.
I recommend starting out with the meter on the 100 vac
scale if using the resistor method.

Hope this helps.
Fr. Tom McGahee