Patent GB-638276-A (GB)
Title: Rectifier with transductor for voltage regulation
IPC: G05F1/32
Filed: 1946-11-15
Abstract: 638,276. Automatic voltage and current control systems; rectifying; charging batteries. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. Nov. 15, 1946, No. 33907. Convention date, Nov. 16, 1945. [Classes 38 (ii) and 38 (iv)] In a voltage regulated A.C./D.C. converter system employing a rectifier and a saturated reactor (transductor) a movable contact electromagnetic or thermal relay effects limitation of the direct current output. In Fig. 1, an auxiliary transducer 7 with opposed windings 8, 9 connected respectively across the output 4 and a fixed direct voltage supply 12 controls through a winding 10 and rectifier 13 the control winding 5 of the input transductor 3, so that normally the rectifier 1 supplies a constant voltage output to the load 4, e.g. a battery to be charged. A relay 16 connected to the rectifier input through a current transformer 15 and rectifier 18 disconnects the current transformer output, and the control current from the winding 5, and instead connects the control current to the relay coil 16 if the input current to the rectifier 1 exceeds a certain limit. At the same time a contact 22 switches in a lower tapped inductance of the main transductor and another contact 20 a holding winding. The latter holds until, through substantial rise in back voltage from the battery 4, the current output of the auxiliary transductor rectifier to the relay 16 is much reduced, whereupon the relay falls back and voltage control is restored. During actuation of the relay the main transductor 3 maintains approximately constant output current due to its control winding 5 being across the constant voltage source 12. The relay may be damped so as only to move a short time after the actuating force has been reached. In Fig. 2 (not shown) the rectified output of. the auxiliary transductor is passed to the input transductor 3 (self-magnetizing winding, not shown) and a thermal relay consisting of a bimetallic strip 23 heated from input current transformer 15 switches out a constant heating source applied to a further heater if the input current is excessive and replaces it by the current from the auxiliary rectifier (13). At the same time a constant voltage is applied to the control winding 5 so that a constant current output is given. On the input current decreasing due to voltage rise across the battery 4, the back control voltage increases reducing the temperature of the further heater and restoring the relay from current to voltage control. The thermal switch may operate with a snap-over action and may act through a relay. In the latter case, several thermal elements at different points of the apparatus may be employed so that the one reaching its critical temperature first operates that change-over. In Fig. 3 (not shown) an electromagnetic relay in the output circuit introduces, when energized, a resistance in the output and a further resistance in the voltage responsive circuit somewhat counteracting the effect of the first resistance. The voltageresponsive circuit may actuate opposed windings of a transductor diffierentially through voltage dependent resistors of oppositely varying characteristics, or, in change to current limitation, may be transformer connected to form a current responsive control, return to voltage control being effected by a voltage responsive relay. Specification 557,829 is referred to. The Specification as open to inspection under Sect. 91 comprises also (Fig. 3, not shown, Cancelled), a thermal strip short-circuiting one or more parts of a resistance in the voltageresponsive circuit above on certain temperature and thereby reducing the current, the circuit design then maintaining it constant. This subject-matter does not appear in the Specification as accepted.