On Monday, November 4, 2019 at 11:47:31 AM UTC-5, Bob Engelhardt wrote:

Another thought - Ward-Leonard's main business was motor controllers,
So the theatrical use assumption may be wrong.


Keep in mind that the Kleig Light (Carbon-arc) and mercury-vapor lamps, some of which are dimmable to a point, are reactive loads. And, the Kleig light as stage lighting persisted into the 1970s on movie sets (with proper filtering against dangerous actinic wavelengths) and mercury-vapor devices are still used in some lighting designs. So, if a lighting device required a strike function, and repetitive in some cases, that would certainly de-rate the Variac as compared to a simple incandescent/resistive load.

Note also that brush-type AC motors may have variable speed controls - such as on your corded hand-drill. I can think of any number of devices that would use such a motor and also allow for the use of a large Variac. A theatrical variable wind machine comes immediately to mind.


Peter Wieck
Melrose Park, PA