| 摘要 |
<p>PURPOSE:To prevent a gate circuit and a GTO element from damaging by eliminating the outputting an ON signal at the GTO during OFF operation when all GTOs are conducted. CONSTITUTION:A DC power source ED is applied through a filter reactor FL and a filter capacitor FC to a 3-phase inverter having GTOs, and its output is supplied to a 3-phase induction motor IM of a load. Voltages of the respective phases are detected by DC voltage detector DCVD, and input through a phase shortcircuit PSDC to one input terminals of AND gates AND1, 2 provided at respective arms. Thus, a signal which immediately turns ON the GTO of OFF state when a phase shortcircuit detection signal 1 is output during normal operation is output from a gate signal circuit GAS. The GTO during turning OFF operation at the phase shortcircuit time is not applied with a forcible ON signal 3 but holds OFF state, and FF is reset by a reset signal 6 at an arbitrary time.</p> |
