| 摘要 |
CONTROL SYSTEM FOR TWO-PHASE REVERSIBLE MOTOR : By closing a series-connected first solid state switch, such as a triac, AC line voltage is applied directly to the first of two field windings of a two-phase reversible AC induction motor to drive the motor in one of its two directions. The shifted phase voltage, appearing at the other or second field winding, has a magnitude of about twice that of the line voltage and is employed to supply gate current to the first solid state switch over a cross-coupling circuit. Conversely, when motor rotation in the opposite direction is desired a second solid state switch or triac is rendered conductive to apply the AC line voltage directly to the second field winding, the gate current for the second solid state switch being derived from the high magnitude shifted voltage appearing at the first winding. Since the gating voltage is phase displaced (by approximately 90.degree.) with respect to the AC voltage applied to the main terminals of the gated triac, the gating voltage will have a relatively high instantaneous amplitude each time the applied AC voltage crosses its a-c axis, namely, goes through zero amplitude. As a result, the triac will be immediately regated at the start of each half cycle. In effect, the triac will be DC gated. |
