| 摘要 |
1,123,542. A.C. motors with D.C. excitation; control of A.C. motors. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 16 Jan., 1967 [11 Feb., 1966], No. 6176/66. Headings H2A and H2J. In a brushless synchronous machine, e.g motor, arrangement whose field winding Fm is provided on its rotor and is energized from a co-rotating armature (E), Fig. 1, of an A.C. exciter over a rectifier bridge (RB) which is mounted for rotation with the machine and exciter rotors, and which includes a resistor R which limits the field winding terminal voltage to an acceptable value during starting and thyristors (T 1 , T 2 ) and T 3 which act as switches to shunt the rectifier bridge during starting and the resistor during synchronous running,. the resistor-shunting thyristor T 3 has its trigger connected to receive a train of pulses from a relaxation oscillator circuit which comprises a uni-junction transistor VT1 operable in response to D.C. excitation voltage produced by the arrangement. During starting, such voltage from the bridge (RB) increases until a Zener diode 24 breaks down whereupon the circuit comprising transistor VT1, capacitor C1, and resistors R3 to R6 produces in resistor R5 the triggering pulses. In other embodiments there are two or more parallel connected resistorshunting thyristors triggered by either respective or common oscillator circuits. |
