| 摘要 |
<p>An electric motor (30) is coupled to the power lines (A, B, C) by thyristors (36, 37, 38). The motor (30) is braked by triggering the thyristors (36, 37, 38) at the proper times to produce an electro-magnetic field within the motor (30) which opposes the residual magnetic field of the rotor. The proper time to trigger the thyristors (36, 37, 38) is determined by comparing the polarity of the voltage (Vab) across the power lines to the back emf voltage (Vc) from the motor (30). The thyristors (36, 37, 38) are triggered when these two voltages (Vab, Vc) have opposite polarities. The braking circuit (50) also regulates the duty cycle of the thyristors (36, 37, 38) to control the magnitude of the current applied to brake the motor.</p> |
