Patent GB-115564-A (GB)
Title: Improvements in Phase Balancers or Phase Converters for Polyphase Distributing Systems.
IPC: H02K57/00
Filed: 1917-08-30
Abstract: 115,564. British Westinghouse Electric & Manufacturing Co., (Westinghouse Electric & Manufacturing Co.). Aug. 30, 1917. Alternating-current commutator and induction machines; rotary converters and transformers; exciting; dynamos, regulating. - Relates to phase-balancers for maintaining an equal division of the load among the several phases of a polyphase distributing system and consists in supplying to one of the windings of the phase-balancer from an auxiliary machine polyphase currents having double the frequency of the main systems so as to compensate for the unbalancing-component of the load. The phase-balancers may be operated as phase-converters to transform a single-phase current (or polyphase currents of one number of phases) into balanced polyphase currents of another number of phases, and vice versa. In one arrangement, Fig. 1, in which a single-phase load circuit 5 is supplied from a polyphase distributing system 2, 3, 4, the phase-balancer 7 comprises a star-connected rotor winding 9 and salient-pole stator windings 12, 13 excited with continuous current from an exciter 14; the stator is also provided with a polyphase " amortisseur " winding 20 which is connected to the rotor winding 21 of a synchronouslydriven auxiliary machine 8. The stator of the auxiliary machine 8 comprises two groups of salient poles displaced by ninety electrical degrees, each group consisting of two north and two south poles; adjacent poles of the two groups have the same polarity. The windings 23 of one group of poles are supplied with current from an exciter 24, and the windings 25 of the other group from an exciter 26. The voltages of the exciters 24, 26 are controlled by two regulators 29, 30 of the Tirrill type connected across different phases of the main system 2, 3, 4. Owing to the separate excitation of the two groups of poles, the phase position of the voltages induced in the winding 21 with respect to those of the machine 7, as well as the magnitude, is varied according to the degree of unbalancing of the load by means of the regulators 29, 30. The exciter 14 is controlled by a Tirrill regulator 17. Double-frequency currents are precluded from flowing through the windings 12, 13 by the use of a resonant arrangement of inductance and capacity 19. In a modification, the machine 8 has a single four-pole stator and is driven by an induction motor, the inducing winding of which is fed from the mains 2, 3, 4 through a variable-ratio transformer. In another modification, the winding 9 of the main machine is stationary and both the continuous exciting current and the double-frequency currents are fed to tappings on a single distributed rotor winding; or the rotor winding may be provided with a commutator and the double-frequency currents are supplied to this winding from the machine 8 through rotating brushes, the continuous-current excitation then being dispensed with; the commutator segments may be connected through inductive or other resistances. In the balancing arrangement for a two-phase distributing system shown in Fig. 4, the stator of the main machine 70 comprises two salient poles 73, 74 and a two-phase " amortisseur " winding 75, into which alternating currents are introduced from the rotor winding 82 of an auxiliary machine 76. The stator of the machine 76 has a two-phase winding 79 which is energized by transformers 80, 81 adjusted by solenoids excited from the main system. The phase of the voltages induced in the winding 82 is varied automatically by turning the stator of the machine 76 in one or the other direction by an induction motor 78, controlled through relays 93 and contacts 96, 97. The phase-balancer in the arrangement shown in Fig. 6 comprises a main induction machine 7 and an auxiliary induction machine 8 having twice as many poles as the machine 7. The stator of the machine 8 is tapped to commutator segments 125 around which brushes 126 are adjusted either by a handle 133 or by solenoids 135. The rotor windings of the two machines are connected together, and the brushes 126 are connected to the rotor leads through star-connected resistances 129 and resonant elements 130 tuned to the frequency of the unbalancing-component currents induced in the winding 120. In the system shown in Fig. 7, the auxiliary induction machine 142 has two stationary exciting windings 143, 144 fed from the. mains 2, 3, 4 through separate transformers 145, 146; the machines 7, 142 have the same number of poles. In the system shown in Fig. 8 the balancer rotor winding 152 rotates at a speed below synchronism, and the stator winding 155 has two phases each connected to two alternating- current machines 147, 148 and 149, 150 of the compensated commutator type. The exciting windings 171 of the machines 148, 150 are connected across opposite points of bridge arrangements 168 of inductance and capacity which act as phase-transforming devices; the pairs of machines 147, 148 and 149, 150 may be replaced by single machines each having two exciting windings. In another arrangement, Fig. 11, a single machine 190 replaces the four machines 147, 148, 149, 150 shown in Fig. 8. The machine 190 comprises four poles 191, 192, 193, 194; the windings on two of these poles are connected to brushes 195, 196 bearing upon commutator segments 198 joined to tappings on a stationary series compensating winding 200. The windings on the other two poles are connected to brushes 207, 209 bearing upon the rotating commutator 205 of a winding 206 rotated by the main balancing machine 7. Two more brushes 203, 204 bear both upon the commutator 205 and upon a segmental commutator 201 connected to the compensating winding 200. All the brushes are mounted on an adjustable bracket 197. Singlephase machines may in certain cases be substituted for the polyphase auxiliary machines.