| 摘要 |
1,236,009. Control of A.C. motors. GENERAL MOTORS CORP. 18 Dec., 1969 [25 March, 1969], No. 61669/69. Heading H2J. [Also in Division G3] A vehicle drive system comprises a polyphase generator 10 coupled to a prime mover 13, the output winding 14 of the generator being connected through a converter 26 to a traction motor 34 having a three-phase stator winding 36 and a field winding 42. The converter 26 has six controlled rectifiers associated with each phase-line 28, 30, 32 and supplies square wave voltages to the motor windings. A trigger circuit 74 for the converter 26 determines the switching frequency of the rectifiers and is connected to a sensor 70 having a slotted motordriven disc 70A controlling the coupling between transformer windings 70B, 70C. A throttle valve 76 for the engine is coupled to accelerator pedal 78 and to a potentiometer 80 connected with lead and lag networks 86, 88 and operational amplifier 90. The output of the amplifier is applied to a field controller 18 for the generator. The amplifier also receives signals from tachometer generator 96 representing the engine-speed. If this speed deviates from the value called for by the potentiometer 80, the field current is varied to change the engine-loading in a corrective sense. If the pedal 78 is suddenly depressed, a voltage is transmitted directly through network 86 to increase the field current temporarily. This input signal then subsides gradually due to network 88. A tachometer generator 108 is driven by the motor and supplies a signal to the amplifier 90, whereby the field excitation of the generator is reduced when the generator frequency (indicated by the tachometer generator 96) is less than a fixed multiple of the motor frequency. This reduces the load on the engine and permits an increase in speed and output frequency of the generator. In this manner reliable operation of the converter 26 is maintained and shortcircuiting between controlled rectifiers is prevented. Over-riding control is provided by a potentiometer 82 which is coupled to the pedal 78 and operates to prevent lurching of the vehicle when the engine speed is high and the vehicle is accelerating from a stationary position. If the cathode voltage of the diode 120 is lower than that of diode 95, the accelerator pedal controls field current rather than the closed loop comprising the potentiometer 80. A governor control circuit 104 receives a signal from the tachometer generator 96 whereby a solenoid 272 is energized to close valve 278 and throttle the engine when its speed becomes excessive. The voltage developed by the tachometer generator 108 is also operable to throttle the engine when the vehicle speed becomes excessive. A transistor is biased through a circuit comprising the tachometer generator 96 and a zener diode. When the latter breaks down, the transistor conducts and turns on a further transistor which energizes the solenoid 272, Fig. 6 (not shown). |
