Re: MOT current draw question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "rheidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

I am going to speculate, I know this is dangerous socialy. A circuit breaker
is an average power device not a peak current device. If your measured
current is of short duration pulses your current transformer could be
correct, but the average power may be less than the trip power of the
breaker. If you use a scope you con prove what is actualy happening. I use a
demonstration to illustrate voltage in a series circuit to my students. I
give them a multimeter, a coil a capacitor and a lamp in series. I turn the
lamp on at full brightness on AC.The students measure the voltage of each
component and get a sum of voltages well over the applied source. Then we
study phase and true power relationships. With out some time/phase
indication you dont know what is real in your observation. The reflected
shorted turn current could give you a non sine wave pulse confuguration or a
resonant peak. Use a scope and see what is happening.
  Robert  H  

> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Fri, 18 Jan 2002 21:57:09 -0700
> To: tesla-at-pupman-dot-com
> Subject: Re: MOT current draw question
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Fri, 18 Jan 2002 22:01:15 -0700
> 
> Original poster: "Marry Krutsch by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <u236-at-earthlink-dot-net>
> 
> 
> Hi again.
> 
> I'm sorry, I wasn't clear as to what I was measuring.  I did my tests
> with individual transformers, one at a time, with the outputs shorted.
> One of my MOTs pulled 40 amps, according to the current transformer.
> The transformer is not damaged, and can run on a 15 amp breaker for
> quite a while before the breaker trips.  I'm just not sure why my meter
> says it's pulling 40 amps.  If that was true, my breaker should trip
> *FAST*, shouldn't it?  I also had a voltmeter hooked up so I could do
> true wattage measurments.  According to my math, at 39 amps and 95 volts
> one MOT was pulling almost 4000 watts.  This can't be right, so can
> somebody tell me what I'm doing wrong?
> 
> Thanks again,
> Winston K.
> 
> 
> 
> Tesla list wrote:
>> 
>> Original poster: "Marry Krutsch by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <u236-at-earthlink-dot-net>
>> 
>> Hi all.
>> 
>> I just got a new current xfmr, and used it to measure the current
> draw
>> on all my HV xfmrs.  My copier trannies measured acuratly at 8.4 amps,
>> but my MOTs were a different story.  According to the current xfmr and
>> Fluke meter they pull between 20 and 40 amps!  That can't be right,
>> since I did the test on a 15 amp breaker which is supposed to trip at
>> 17.5 amps.  What is happening?  How can I get an accurate measurment?
>> 
>> Thanks,
>> 
>> Winston K.
> 
> 
>