GB1516693A - Electrical power supply circuits - Google Patents

Abstract

1516693 Rectifying; control of A.C. motors SIEMENS AG 17 June 1975 [20 Sept 1974] 25675/75 Headings H2F and H2J A supply circuit to maintain a constant D.C. output voltage across terminals 3, 4 irrespective of the presence of a high or low supply voltage (e.g. 220 V or 110 V) at A.C. supply terminals 1, 2, comprises a rectifier bridge D1-D4, capacitors C1, C2 and a switch or bridging link S 1 operable to disconnect terminals 5, 6 when the supply voltage is high, capacitors C1, C2 then performing a smoothing function, and to connect terminals 5, 6 when the supply voltage is low, so that members D1, D2, C1, C2 act as a voltage doubler and diodes D3, D4 remain non- conductive. If the D.C. load across terminals 3, 4 is continuously energized and is associated with an A.C. load of relatively small power (e.g. a fan motor in a teleprinter system), then by connecting the motor M to the circuit as shown, it will always be energized at the low A.C. voltage irrespective of the value supplied at terminals 1, 2. If the D.C. load is not continuously energized, a circuit as shown in Fig. 2 is used and a change-over switch S2 is operated to its lower or upper position according to whether the A.C. supply voltage is respectively high or low, consequent energization of the whole or half of the primary winding L1 of a transformer causing the voltage applied to the motor M to remain the same. If the motor is of the type having selectable windings designed for two different voltages, the transformer may be omitted and the switch S2 operated to selectively connect the terminal 2 to one or other of the motor windings.