| 摘要 |
1,035,071. Automatic voltage control. ROBERT BOSCH G.m.b.H. April 5, 1963 [April 7, 1962],No.13584/63. Heading G3R. In a voltage regulator of the kind in which the field winding of a generator is connected in series with a main transistor controlled by a second transistor in dependence upon output voltage variations, the transistors are protected against possible overload, should a short-circuit occur in the field winding, by a circuit including a semi-conductor controlled rectifier. As shown, a main transistor 26 connected in series with the field winding 16 of a generator 15 is controlled by a second transistor 27 in dependence upon output voltage variations whereby the field current is varied to counteract these variations in known manner. Resistors 28, 29 and a diode 30 connected in series between the positive lead 18 and the base of transistor 26 ensure excitation when the generator starts from standstill. The overload protection circuit includes an input resistor 40 and a potentiometer 41 connected in parallel between the transistor 26 and the negative lead 20, and a semi-conductor controlled rectifier 42 having its anode connected to the collector of transistor 27 and to the junction of resistors 28 and 29, its cathode connected to negative lead 20, and its control electrode connected to the slider 44 of potentiometer 41. The arrangement is such that if excessive current flows through transistor 26 because of a fault in the field winding 16, the increased voltage at slider 44 renders the controlled rectifier 42 conductive so that transistor 27 is short-circuited by a low impedance path; also, the current flowing through resistor 28 and rectifier 42 is of such magnitude that the main transistor 26 returns to its blocked condition. Transistor 26 is thus protected and the circuit returns automatically to normal operation when the fault is removed. In a modification (Fig. 3, not shown), for use with a generator having an operating voltage of about 100V, a diode is connected in series with the controlled rectifier and the junction between the diode and the rectifier is connected to a tapping point of a voltage divider shunting the output terminals. |
