GB497521A - Device for automatically regulating the voltage of an electric power supply system - Google Patents

Abstract

497,521. Electricity supply ; transformers. UNION ELECTRIQUE DU CENTRE. March 4, 1938, Nos. 6899 and 6900. Convention dates, March 6, 1937 and Feb. 9, 1938. [Classes 38 (ii) and 38 (iv)] Boosting by transformers; balancing.-A polyphase induction regulator is used to introduce in series with a supply a voltage varying automatically with the load. The rotor 2 is permitted to rotate in proportion to the load current against an opposing torque supplied externally by springs 4, weights or hydraulic or pneumatic means, or internally due to iron losses or eddy currents. When using internally produced torque to balance the torque due to load currents, it is preferable to connect the primary windings to the supply mains after the secondary windings. In order to overcome the negative boosting effect in the third quadrant of each cycle which occurs in a simple arrangement of this kind, two devices are arranged with their secondary windings in series and the connections are such that their fields rotate in opposite senses. In dealing with phase-shifted currents (power-factor less than unity), a negative booster is preferably excited at a higher voltage than the positive boosting element, through a variably tapped transformer, or through a zigzag wound auto-transformer if it is also desired to balance the phases. A double apparatus giving a boosting voltage practically independent of the phase displacement of the load current has its two rotors on one shaft and angularly displaced 180‹ + the mean value of the phase shift. The negative booster elements may have a greater number of poles than the booster. Both elements can be arranged on a single magnetic circuit, Fig. 10, for example, the primary winding 21 of the booster being on the stator and its secondary 22 on the rotor, while the primary winding 23 of the negative booster is on the rotor and its secondary 24 on the stator. The primary windings are wound to produce fields rotating in the same direction. As in the double apparatus, the secondary windings, which are in series in the supply mains, are arranged to produce in the no-load position a nil resultant or a voltage in quadrature with the supply voltage. The torque produced. by the interaction of the primary windings in this arrangement may wholly or partly replace the external opposing torque since, through independent of the load, it varies proportionately with the angular displacement of the rotor due to load. To improve the operation with dephased currents, the ratio of the primary turns may differ from unity. The apparatus may operate to balance the phase voltages if used with a zigzag winding and equal turns in the primary winding.