50kva saturable reactor for globar hi-temp heat treat furnace

[TonopahJoe]

I work in an land that time forgot with equipment still in service from the 1930's. Things were built to last in those days. Some of our heat-treat furnaces have silicon carbide heating elements (aka "globars") equipped with saturable reactors (aka magnetic amplifiers) that regulate the current and voltage to single phase transformers that supply the globars. So one leg of the 480vac supply goes through the first coil of the reactor, exits the other reactor coil and into one side of the single phase step down transformer. The reactor coils is 180 deg out of phase with each other. The other 480v leg bypasses the reactor and goes to the other tap of the transformer. A 4-20mA output from a temperature controller regulates the output of a 0-10A rectifier which in turn regulates the DC coils wrapped around the reactors AC coils, which varies the magnetic saturation of the reactor, which in turn regulates the AC current and voltage flow. Old school but very reliable and well suited for a foundry environment.

The minimum AC current I've measured is 95 amps when the temperature is well above setpoint and the temp controller is outputting 4mA. I'm still seeing 0.3 DC amps coming out of the rectifier, however, that's with an oversized clamp-on meter so I'm not sure that I believe that reading. I've measured output voltage up to 100 volts across the globars with a current above 400 amps. DC current measures 1.4 amps at this output.

I wonder if anyone can tell me what output range to expect of the reactor. Can it be "choked" down to 0 amps AC, or close to it?

 

[gar]

150922-2143 EDT

TonopahJoe:

A saturable reactor has a finite impedance when the control signal is zero. Thus, you can not throttle your load current to zero.

For a useful discussion see Osborne Transformer a local Detroit custom transformer manufacturer.

See:
http://osbornetransformer.com/saturable-reactor-winding-configurations/
http://osbornetransformer.com/produ...r-inductors/?gclid=CPGZ9JWBjMgCFYk7aQodjfQJcg
also
Do your own searching on the Internet.

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[GoldDigger]

Do your own searching on the Internet.

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But how do you know which reference to believe?
(Admittedly not quite so difficult a task for the kind of question involved here as for general net searches.)

 

[gar]

150923-0652 EDT

GoldDigger:

I see too many questions ask on this forum where the questioner has done little research on their own before asking a question here.

How do you know whether Internet information is valid? Same question applies to this forum.
Cross-correlation between different sources.
Judgement based on your own background.
Your own experiments.
Your library.
Common sense.
Asking questions here after you have done some other research.

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