POWER TOOL WITH A PROTECTIVE CONTROL MODULE

摘要

A power tool configured to receive an alternating current (AC) input signal, comprising an electric motor (14), a phase-controlled switch coupled in series with the motor (14), a motor control module (18) interfaced with the phase-controlled switch that modulates the conductive state of the phase-controlled switch in relation to a zero-crossing of the AC input signal and a protective control module (22) that measures voltage across the phase-controlled switch during a non-conductive state of the phase-controlled switch after a zero-crossing of the AC input signal but prior to closing of the phase-controlled switch and disables the power tool when the measured voltage indicates a malfunction of the phase-controlled switch.