Patent GB-1402322-A (GB)
Title: Drive system incorporating a battery
IPC: B60L11/18
Filed: 1972-07-26
Abstract: 1402322 Control of A.C. motors KG ENG LABORATORIES Ltd 4 May 1973 -[26 July 1972] 35009/72 Heading H2J An electrically-driven vehicle 1 comprises wheels 2, 3 of which the former are driven through a gear-box 4 and clutch 5 by a two phase squirrel cage induction motor 6 supplied from a battery 12 through an inverter 11, which includes controlled switches such as thyristors or transistors and diodes in each of its phases, Fig. 2 (not shown) and which is controlled by a signal produced by an adder 8 supplied with a motor speed signal from a tacho-generator 7 and with a signal representative of desired slip speed from a potentiometer 9 operable by an accelerator pedal 10 over two consecutive ranges of movement from a rest position, during the first of which the slip speed signal progressively decreases from a maximum negative value to zero and during the second of which the signal progressively increases from zero to a maximum positive value, the variation of the signal causing corresponding variation of the frequency and voltage of the inverter 11 whereby during the first range the motor 6 is regeneratively braked to charge the battery 12 and during the second range the motor 6 produces positive torque to drive the wheels 2. In a typical starting and accelerating operation, a "catching" circuit produces a minimum inverter frequency to run the motor up to an idling speed with the gear-box in neutral and the accelerator pedal in its rest position, after which the operation of members 4, 5 and 10 accelerates the vehicle in a manner similar to that for an enginedriven car, the return of pedal 10 to its rest position for each de-clutch and gear change producing momentary regenerative braking through the clutch until the pedal 10 reaches its second range during the subsequent accelerator depression. Whilst the regenerative braking produced by the pedal 10 is sufficient to slow the motor during upward gear changing, increased regenerative braking followed by mechanical braking is obtained by operation of a brake pedal 21 controlling, in the first part of its travel, a potentiometer 20 supplying a negative signal to the adder 8 and, in the second part, the master braking cylinder of an hydraulic braking system, a lost motion linkage keeping the potentiometer 20 in its maximum negative bias position throughout mechanical braking, irrespective of the position of the pedal 21. The potentiometers 9, 20 may be replaced by variableinductance electromagnetically operated transducers (30, 31), Fig. 6A (not shown), or by photoelectric transducers. Charging of the battery 12 can be effected from an external A.C. supply by a change-over switch (40) connecting the inverter 11 to the motor winding (50) or a transformer (41) connectible to the A.C. supply, Fig. 7 (not shown). If the vehicle has an automatic gear change mechanism, operation of the latter may cause the application of a "regenerative braking" signal to the inverter during each upward gear change. Typical operating characteristics are discussed, Figs. 3, 4, 5, 6B and 6C (not shown). The members 4, 5 may be omitted and the motor 6 directly connected through gearing to the wheels 2.