high voltage testing of 208VAC phase controller used on semiconductor production equipment

This phase controller uses the tried and true back to back SCR technique. It’s and old unit but still in service, partly due to our repairs and system debug. About half the gear in the photo is our test jig. Watch out for ‘flux doubling’ when you turn on/off that big toroid transformer! We kept blowing the 20A breaker until we set up the variac on our bench set up.

Phase controller power supply under test on our bench. The light bulbs provide a test load, the toroid allows us to use 110VAC to supply the test unit with 208VAC.

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