Re: x-ray transformer questions

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

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


Most of the larger units, such as yours, have a 7.5 - 10 kVA core.  Measure
your core dimensions and I can give you a better estimate.  Core cross
section is one of the most important factors with regard to the magnetic
flux.

The 7.5 - 10 kVA rating is approx 75% duty cycle but can be exceeded for
short periods of time such as charging up large Marx bank caps, etc.

If you plan to run it constant, they you would be wise to operate at 5-6 kVA
as a maximum.

The reason the power levels are not specified is because different types of
buck/boost reactors (external) were used with these xmfrs, so ratings depend
on heat rise vs. time.  You could determine the proper rating by operating
the xmfr in sec short circuit condition and carefully monitoring the core
temp with a thermister.  Many modern multimeters have these probes.

Core temp vs. time will give you a reasonable estimate of how much power you
can operate at.  Core temp should not exceed 180 degrees F. (max) for most
applications.  You can carefully dry off a section of core and wipe clean
with a solvent.  Then, using conductive epoxy, attach your thermister.  Be
sure to keep this conductive epoxy away from the HV coils.

Keep the core temp below 175 degrees F. with long run times and you should
be ok.

This was our approach on a large X-ray xmfr we used to charge a 100 kV Marx
bank.  It worked out to approx 12.5 kVA for short duty cycles less than 25%.

Be extremely care --- these things are killers.  We attached a large red
rotating beacon to one side of the 220 to ground (120 VAC) so the beacon was
on any time HV was on.  Use a relay so it will energize as soon as your
control circuit applies any voltage to the primary of the xmfr.

Dr. Resonance

 >
 > Tonight's questions concern a Westinghouse x-ray transformer.  There are
two
 > things I'm wondering about with this unit: its specs and input/ output
 > information.
 >
 > Here's what's on the label:
 > cycles 50/60
 > wiring 3D 8939
 > style 981928
 > Volts AC, KVA, and Amps are all blank.
 > Under the word "Westinghouse", there are the following tiny numbers:
36233-D
 >
 > Can anyone figure out the complete specs with this info?
 >
 > Now for the input connections:
 > XFL, XFC, XFS, G, MA, A, AA
 >
 > Input hookup info?
 >
 > And, finally, there are two high voltage recessed terminals.  One has a
 > single center conductor; the other side has three (their purpose?).  The
 > diameter of the sockets is 1.25".  I did manage to obtain some high
voltage
 > cable at one point, but the end diameters are too large.  I'm considering
 > making new ends out of epoxy or if I could obtain the correct size cable
 > economically, I would go with that.
 >
 > Dimensions are about 13.5x17x15 inches and it must weigh at least 250 lbs
I
 > would guess.  Not sure what I'm going to use it for, but my purpose right
 > now is to just find out about it and get it going, using an appropriate
 > variac for current limiting of course.
 >
 > If anyone has any info on this or a similar unit, I would appreciate your
 > sharing of it.
 >
 > Thanks,
 > Jack
 >
 >
 >