GB835210A - Improvements in or relating to electrical generator regulating sí¡í¡ems, especially for mechanically propelled vehicles - Google Patents

Abstract

835,210. Automatic voltage control systems. BOSCH G.m.b.H., R. July 12, 1957 [July 14, 1956], No. 22091/57. Class 38 (4). The output voltage of a self-excited D.C. generator is controlled by a transistor in series with the field winding, and the transistor is controlled by a voltage-sensitive transistor oscillator. A transistor 110 is connected in series with the field winding F across the armature G and the base bias is derived by rectifying the output of a mono-stable blocking oscillator consisting of a second transistor 120 and a transformer 121. The emitter of transistor 120 is biased negatively by a battery H with respect to the base so that the transistor 120 only conducts when the generator voltage exceeds a set value. When transistor 120 starts to conduct, one cycle of oscillation occurs. The resulting voltage pulse across transformer 121 is rectified at 128, 129 to charge capacitor 135 so as to eventually bias transistor 110 to cut-off and so reduce the generator voltage. Capacitor 135 discharges through resistor 111 to enable the cycle to continue. Load current limiting is effected by causing the load current to heat a temperaturevariable resistor 127 in the base bias circuit of the transistor 120. Surge limiting is effected by a rectifier 136 across the field winding. In a modification, Fig. 2 (not shown), the battery H is replaced by either two rectifiers in series so as to form the non-linear element in a voltagesensitive bridge, or by a Zener diode; and load current limiting is effected by including a resistor carrying the load current in the emitter/base circuit of the transistor 120.