RE: MOT current

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

Original poster: "John H. Couture" <couturejh-at-mgte-dot-com> 


To All -

Big balls of flame.

Putting your life in danger.

You can avoid all these hazards by using a variac and bringing the voltage
up slowly. Even Terry does this.

John Couture

----------------------



-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, October 01, 2003 8:39 PM
To: tesla-at-pupman-dot-com
Subject: RE: MOT current


Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi John,

At 06:08 PM 10/1/2003, you wrote:

 >Hello,
 >
 >I was wondering how one measured the current of a MOT with out putting
 >their life or multimeter at risk. You can not feed it a lower voltage
 >because of it's non linear current behavior(pain in the A$$). any tips
 >would be greatly obliged
 >
 >Thanks
 >
 >John

Not putting you life at risk is easy.  Just stay far away from the test
when you run it.  Don't go holding the meter in your hand or anything.  Be
about ten feet away if anything goes bad...

I assume you mean the short circuit current.  The current is roughly 1.5
amp so any multimeter that can handle that AC current can do it.  You just
hook the meter up across and basically shorting the MOT output, get far
away, turn it on and take the reading before the lights go out.  It draws
about 25 to 30 amps so the house fuse will blow in a few seconds...

One thing not to do is goof up and leave the meter in the voltage
mode.  The meter will instantly go up in a big ball of flame!!  You need
the meter's current shunts basically shorting the MOT output down to very
low voltage.  Best to have the off switch and a fire extinguisher
handy...  Of course, if you don't feel comfortable and confident in doing
the test, just don't!!  If anything goes bad, it will go very bad...

Now for the easy way...  The current is 1.5 amps ACrms.  Just trust
me!!  ;-))  When you do the actual test, the high line current will drop
the line voltage about 10 volts anyway so you are not going to get any
better accuracy anyway.  Just assume the short circuit current is 1.5 amps
and you will be very close.  The one I tested was 1.40 amps short and 1860
volts open circuit.

Cheers,

          Terry