Gerald,
Comments embedded below:
73, Jim - w5ifp@gvtc.com
>> -----Original Message-----
>> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of
>> Gerald Williamson via Amps
>> Sent: Saturday, April 9, 2016 7:17 AM
>> To: kd4lyh@yahoo.com; amps@contesting.com
>> Subject: Re: [Amps] Control transformers
>>
>> Jeff, I have not done that but conceptually it should work well.
If
>> you use two of the 3kva transformers, one would expect to
>> generate enough d.c. to supply a 6 KW load.
>>
>> The voltage doubler will charge the filter C to 2.8 times the rms
>> voltage so two of the 600v units would have a no load voltage of
>> 3394v and full load maybe 3100v or so.At 6 KW, the current could
>> be upwards of 1.7 amps.
>>
>> There are other considerations such as the much higher peak
>> currents caused by a C only filter that would tend to reduce the
>> current capability somewhat to prevent over heating the
>> transformers. Fortunately the copper losses are related to
current
>> squared so a modest reduction in current equates to a large
>> reduction in heating.
>>
>> You would wise to find a way to test the insulation break down
>> between windings and the core. Perhaps you could build or borrow
>> a break down tester.
>> They are very easy to build based on an old microwave oven
>> transformer.
>>
>> For a very rough test, you could connect a 100w incandescent
light
>> bulb in series with the 120 or 240v primary and connect the 600v
>> windings in series. One end of the 1200v can be connected to the
>> core and that would subject the other end of the 1200v winding
to
>> about 1700v peak. If the 120v windings were connected in
parallel
>> and 240v applied, the secondary voltage would then be about
>> 3400v peak.
[W5IFP] Did you really mean "connected in parallel" ?
You can't run it this way but fine for a brief test. The
>> light bulb will limit the current flow in case there is a
breakdown. It
>> will also give a relative indication of the amount of leakage in
the
>> transformer. One would expect only a dim glow if all is well.
Also, it
>> would be a good idea to connect the two transformer cores
>> together and to ground (or neutral) for the brief test. Be
careful as
>> bad stuff can happen!
>>
>> 73,
>> Gerald K5GW
>>
>>
>>
>>
>> In a message dated 4/8/2016 11:16:07 P.M. Central Daylight Time,
>> amps@contesting.com writes:
>>
>> Good day,
>> I have learned alot from this list over the years. What I
propose to
>> try may work or it wont. Im thinking it wont work but it dont
hurt to
>> ask. From time to time I come across 1kva,2kva,3kva control
>> transformers. 0 -120v on one side and 0 -240,480,575,600 volts
on
>> the other. If I was to series two of the 600 volt windings then
feed
>> a fullwave doubler, would this work or not? I would also like to
>> series the 120v side feed it 240v. For there intended purpose I
think
>> with control transformers, the higher voltage winding serves as
the
>> primary and the secondary is the 120v winding. Not sure how
>> robust machine control transformers are.or if there is enough
>> insulation between primary and secondary. Im sure current
>> capacity would drop if I step up the voltage.
>>
>> Jeff
>>
>> KD4LYH
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