RE: Ammeter readings with MOT power supply

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Breneman, Chris" <brenemanc@xxxxxxxxxxxxxx>

Thanks, but I'm still somewhat confused.  If the problem actually is 
the circuit breaker, that would mean that the 15A breaker wasn't 
tripping when more than 20A were flowing through it for several 
minutes.  That link says that they can take a while to trip if the 
current is only slightly over the limit, but I would think that over 
5A over the limit of a 15A breaker should be enough to trip it 
quickly.  Also, I'm using a circuit breaker that's newly bought, and 
I don't think it's a FPE breaker.  It says "Type-Q" on it if that's any help.

Thanks,
Chris



-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Wed 3/28/2007 8:59 PM
To: tesla@xxxxxxxxxx
Subject: Re: Ammeter readings with MOT power supply

Original poster: David Dean <deano@xxxxxxxxxxxxxxxx>

Hi

Unless you are using old FPE breakers that were popular in the 1960's and
1970's, which have a bad reputation for never tripping, it may take a while
for the breaker to trip. See http://www.swgr.com/CircuitBreakersTech_Home.asp
for a better explanation than I can give.

later
deano

On Tuesday 27 March 2007 19:40, you wrote:
 > Original poster: "Breneman, Chris" <brenemanc@xxxxxxxxxxxxxx>
 >
 > Hello,
 >
 > I've almost finished the MOT power supply for my first Tesla coil,
 > but have a few questions about its operation.  The supply consists of
 > two MOTs with the primaries in parallel and secondaries in series and
 > a third MOT in series with the parallel arrangement of the first two
 > acting as a ballast.  The ballast has its high voltage winding
 > shorted.  All of them run on 120V.  In addition to the transformers,
 > I also have a 15A circuit breaker in series with the circuit, and the
 > house has its own 15A breaker on this circuit.
 > I recently received a 15A analog panel ammeter which I wanted to use
 > in the circuit to monitor current drawn.  It is placed in series
 > between the breaker and the ballast.  When I run the power supply
 > with the hv end shorted, no breakers trip, but the ammeter reads off
 > the scale.  When I replaced the analog meter with a digital
 > multimeter capable of reading up to 20A, it read "Overload".  What I
 > don't know if if more than 15A is really flowing, and if it is, why
 > it isn't tripping the breakers, and if it isn't, why do the meters
 > show that it is?
 > The only possible cause I can think of for this discrepancy is that
 > the power factor is probably greatly offset by the highly inductive
 > load, but why wouldn't the breakers trip in this case?  I also tried
 > the circuit with a 10uF PFC capacitor, and saw no difference in
 > behavior.  If the problem is the power factor, do you think a 180uF
 > PFC capacitor would be reasonable for such a supply?  The open
 > circuit voltage is slightly over 5kV and the short circuit current is
 > slightly over 500mA (that is, assuming these readings from the
 > digital multimeter are correct; I determined these values indirectly
 > by measuring current through different resistances on the hv side).
 >
 > Thanks a lot,
 > Chris