| 摘要 |
<p>1535748 Automatic control of current and speed GENERAL ELECTRIC CO 19 Dec 1975 [20 Dec 1974] 52125/65 Heading G3R The current taken by an electric motor is limited by controlling the power supply in dependence on a direct comparison between measured motor current and a time-varying reference signal. The periodic generation of the reference signal is dependent upon a given condition in the supply circuit. As shown in Fig. 1, a load 14 is driven by a D.C. motor 10 supplied from a three-phase source 19 over a thyristor bridge circuit 18. A tachogenerator 30 produces a voltage proportional to the motor speed for comparison with a manually set desired speed signal in a circuit 26. The resulting error signal controls the production of thyristor firing pulses in a generator 20. The error signal is prevented from reaching the pulse generator 20 if an inhibit signal is produced on a line 54 by a current limiting arrangement 40 responsive to the output of a current sensor 52 fed through a bridge rectifier 48. Voltage limiting is also provided by a feedback line 34. The current limiting arrangement 40 includes a sawtooth reference voltage generator 42 which is periodically reset by a signal on a line 45 produced whenever a thyristor firing pulse is produced by the generator 20. The reference voltage is supplied to a comparator 44 together with the measured current signal from bridge 48. When the current signal exceeds the instantaneous reference voltage value, the inhibit signal is produced on line 54. Examples of the circuits 42, 44 are described with reference to Figs. 2 and 3 (not shown).</p> |
