Phase Cut or Phase Chop control

On Fri, 19 Jan 2007 18:53:50 GMT, "Fred" proclaimed to the world:

In this control scheme, power to a load is varied by using a power transistor, triac, or diac to turn on at some point in the phase of the supply power cycle. The electronics "chop" a portion of the sine wave and deliver it to the output.

This is a very simple and efficient way of varying OP power. Since the power transistor is either off or in full conduction, there is less heating and it can handle higher loads. Since a triac shuts itself off automatically on phase crossing, the control circuit only needs to time the on pulse to whatever percentage of the AC wave it needs to supply the correct amount of power.

It is normally used with resistive loads like heaters. I've seen it used in early motor controls.

Hey Paul!

Thanks for the info... much appreciated.

Fred