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From: Ted Busky
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Subject: Re: 115 VAC single to 3 phase converter
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NNTP-Posting-Date: Sun, 22 Dec 2002 19:43:11 EST
Date: Sun, 22 Dec 2002 19:53:19 -0500
400HZ phase and without a separate converter? That is a challenge. What kind of 3
phase load do you have, 3 phase motor, inductive or resistive? I assume that the
load is either 3 phase motors and/or single phase transformers and single phase
motors with little direct connected resistive loads like heaters. The options I
know of are:
A. If you have 3 phases of inductive, 1phase motor, or resistive load you might be
able to re-wire the load to work on single phase from your 400hz generator.
B. You could convert the load to work on 60hz by changing to 60hz transformers and
motors. You might need to beef up the filter caps in power supplies converted from
400hz to 60hz.
Otherwise, option 1 below comes closest to your "without a separate converter"
1. Static converters work for motor loads. Essentially you apply single phase power
to 2 phases and start the target motor by spinning by hand or momentarily switching
in a phase shifting capacitor to the third phase start the motor. This only gives
50% to 66% of the motor's output. Also, the generated phase is not as "strong" as
the other 2, so you should not connect resistive loads to other than the applied
single phase. Packaged converters are available as already posted from enco and
other machine tool suppliers. Phase-a-matic http://www.phase-a-matic.com/ makes
static converters and they have some helpful information on their web site. I have
some information on sizing the starting capacitor for various horse powers but on
60hz. You could use this as a base to start with for 400hz.
2. Static converter with idler motor. Rather than start the target motor directly,
you first start an idler motor that is 50% bigger than the target motor using the
methods discussed above. Then, turn on the target motor and you will get nearly
100% power from the target. Also, since phase 3 is already generated, the target
motor will start on its own. This still has the weak generated phase problem, so
you want to connect your resistive loads to the single phase input. . 60 hz 3 phase
idler motors are readily available at scrap yards for a few dollars. I don't know
where you might find a 400 hz motor other than military surplus.
3. A rotary converter will provide the power you need on all three generated
phases. However, you will need to find a 400hz unit.
4. As already posted, you can use a variable speed drive that accepts single phase
in and generates 3 phases electronically. This is quite a quite slick one box
solution if you can find a drive for 400hz. From my experience they are generally
for 60hz induction motors.
5. You can also generate the 3 phases electronically with a 400hz oscillator and
120 degree phase shifter to create the 3 phases. Then with power amplifiers you
generate the volts and amps you need. This is an option for small loads like
synchros and resolvers. But, it takes lots of electronics.
6. You might be able to locate a 3 phase 400hz generator. These can be engine
driven, motor driven or electronic. I know these options are available for testing
50hz systems in the states.
Additional sources: I know there is a ham radio group who specializes in military
gear. While the radios tend to run on DC generators, there might be a 400hz
solution there. Have you checked for any military avionics groups or military
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