We got it from Measurement Canada. They issue documents approving or
disapproving devices for energy metering inspection.

Variacs can have distortion in the laminations...usually slots for some
reason (heat expansion?) that cause the output waveform to have some ringing
in it. I haven't done any scoping or analysis personally and am paraphrasing
NBS information.. Electrical utility meter testboards are frequently
rejected for usage by Measurement Canada for use of Variacs in their
potential and current supplies. I believe some types may pass depending on
the core shape and configuration.

Any transformer with irregular shaped laminations can cause this. They
usually appear as slots for expansion between the E and I laminations or
mounting holes.

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"Rich Grise" wrote in message
...
Where do you get this information? A variac is nothing but an adjustable
autotransformer - what part introduces the distortion?

Thanks,
Rich

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Josepi wrote:
Careful. Variacs are known waveform distorters. The government would not
let us use them for precision power measurements as the waveform adopts
many harmonics in some units.