Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>The original widespread application of variacs was for "incandescent light dimmers" in all the old theaters. These were used a lot between movies on evenings when local plays were presented.
After solid state devices took over this function the quantity produced dropped by a factor of 10 and the price skyrocketed, now, to over $1,100 for a new 1256 variac (220 volt, 28 amp rating). The are usually only used with inductive loads --- something that solid state has not conquered adequately with simple circuitry.
You can use solid state for inductive load control but when the solid state device fails, unlike a variac, the current goes to full "on" condition and the device immediately jumps up to full power. This is one of the main reasons we still use variacs in our commercial coil applications --- safety. Many of the experiments our museum customers conduct with our coils are demonstrated at power settings of 45-70% and not always full power.
I'm always hoping that some of the solid state gurus on this list come up with a safe, reliable, and fail-safe during failure system to control pole pigs and PTs (Dave Sharpe --- are you listening??)
Dr. Resonance
What else can you use these things for? I know it will allow you to vary the AC voltage, but for what application? Rich