GB1042757A - Improvements relating to excitation arrangements for synchronous machines - Google Patents

Abstract

1,042,757. Alternators; converting. LICENTIA PATENT - VERWALTUNGS G.m.b.H. Sept. 6, 1963 [Sept. 6, 1962], No. 35354/63. Headings H2A and H2F. In an excitation arrangement for a synchronous machine, preferably a turbo-generator, having rotating controllable semi-conductor rectifiers connected to a main exciter at least one A.C. generator is provided for supplying firing pulses to the rectifiers and the phase of the pulses may be varied by altering the magnetic axis of the A.C. generator. The magnetic axis may be adjusted either by rotation of its stator or electrically by altering the relative excitation of two control windings mutually displaced by 90 degrees. The associated static apparatus, shown below line 21, includes amplifiers R and resolvers F used to produce signals having the necessary amplitude and phase for feeding the pairs of control windings D6, D7 in the A.C. generators to produce correctly phased firing pulses. These signals are generated from a main control signal Ust which is derived from the voltage generated in the generator winding D2, i.e. the terminal voltage, and the current in the field windings, a voltage proportional to the latter being generated in windings D10, D11. The controllable rectifiers are connected as two counter parallel groups of six elements, each controlled by an A.C. generator and arranged so that one group supplies the whole exciting current for normal operation whereas the other only supplies current intermittently and therefore is of smaller rating. Advantageously, the group which is not conducting is held in a condition of full inverter control by means of the stages 45, 46, 47, 48. The A.C. generator used for supplying firing pulses has a normal rotating polyphase winding (six-phase) connected through a circuit including a saturable reactor, for producing steep fronted pulses, to the trigger electrodes of the semi-conductor devices.