Re: Wire-wound resistors as dummy test load

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

Original poster: "Richard W. by way of Terry Fritz <twftesla-at-qwest-dot-net>" <potluck-at-xmission-dot-com>

List,

Got it. :) This is interesting.
I have 43 50 watt 50K Dale aluminum power resistors. 2 chains of 20 could
theoritically handle 15Kv -at- 30ma for load testing. That calculates to 750
volts at 30ma disspating 22.5 watts each.

I'm a bit leary of trying it though.

The following is vague but...
I don't believe these are good for HV apllications. And I think they're
rated for 600v anyway. I've heard the end caps can blow off.

Rick W.





----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, October 02, 2002 7:00 PM
Subject: Re: Wire-wound resistors as dummy test load


> Original poster: "Peter Komen by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<pkomen-at-zianet-dot-com>
>
> Ed,
>
> Well, let's look at this.
> 200 Ohm 200 watt resister to dissipate 200 Watts will need a current
through
> it of 1 Amp.  Hook 4 in series and run a current of 1 Amp through them,
and
> the dissipation for each resister is still I^2 * R or 200 Watts.  The
total
> dissipation is 800 watts for the 4 in series.  Figure it 2 ways 4 * 200
> Watts = 800 Watts or 1 Amp^2 * 800 Ohms = 800 Watts.
>
> If the resisters are different resistances are the power dissipated in
each
> will not be equal, but if certain things are known about the circuit, the
> power dissipated in each resister can be calculated.  Suppose that we have
> two resisters in series: a 1-Ohm 2-Watt resister and a 200-Ohm 200-Watt
> resister.  If 201V is applied across the two resisters, 1 Amp will flow
and
> the resisters will dissipate 201 Watts; 1 Watt in  the 1-Ohm resister and
> 200 Watts in the 200 Watt resister..
>
> Could explain your reasoning?
>
> Regards,
>
> Pete Komen
>
> > Original poster: "Edward Wingate by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <ewing7-at-rochester.rr-dot-com>
> >
> > Tesla list wrote:
> > >
> > > Original poster: "David Speck by way of Terry Fritz
> <twftesla-at-qwest-dot-net>"
> > <dave-at-davidspeckmd-dot-org>
> > >
> > > Rick,
> > > Sorry, nope, but in series, each resistor will still be able to
> > > dissipate its own 200 watts, quite independently of the other three,
so
> > > four in series will give an 800 ohm, 800 watt resistor, with maximum
> > > dissipation when you put 800 Volts at one amp through the string.  A
> > > single resistor would dissipate 200 watts when carrying 200 volts at
one
> > > amp.
> > > Dave
> >
> > Hi Dave,
> >
> > The wattage rating of resistors in series is only as high as the
> > weakest link which in this case is 200 watts. Each resistor is still
> > being asked to pass an 800 watt total load no matter what each is
> > dissipating separately and it won't work for long. If you splice 4
> > pieces of wire together in series they still will only handle what a
> > single length is rated for in amperes. In parallel the 200 watt
> > resistors could handle 800 watts because each resistor handles 25% of
> > the load.
> >
> > Ed
> >
> >
> >
> >
>
>
>
>