| 摘要 |
<p>1,255,225. Control of A.C. motors. DANFOSS A.S. 13 March, 1969 [16 March, 1968], No. 13316/69. Heading H2J. For controlling an A.C. motor, a direct voltage is applied to a voltage regulator 5 whose output voltage U1 depends upon the setting of a battery-fed resistor Rl. When the current passing through a resistor R2 becomes excessive, the regulator operates to reduce its output voltage. The regulator may comprise an electronic switch associated with an impulse-control circuit for passing, under normal conditions, pulses of fixed frequency but variable width. When the current-limit is exceeded, the repetition frequency is reduced. The voltage U1 is applied to an inverter comprising controlled rectifiers E1-E6 with a common quenching circuit 10 and from which the motor is supplied. A control unit 11 for the inverter is connected to a frequency regulator 12. A control resistor R3 is associated with rectifier 17 and indicator 14 so that the current through the resistor is proportional to the inverter current. Tappings 18, 19, on the resistor R3 each provide voltagesignals for reducing the voltage U1 by different amounts, these reduced voltages being applied to the voltage regulator and frequency regulator respectively for satisfactory motor operation at low speeds.</p> |
