| 摘要 |
1,244,259. Control of two D.C. motors. CONVEYANCER FORK TRUCKS Ltd., and SEVCON ENG. Ltd. 19 Feb., 1970 [25 Feb., 1969], No. 10019/69. Heading H2J. In a traction system having series connected motors A, B, the motor A will tend to accelerate leading to a stalled condition of motor B if the wheel driven by the motor A leaves the ground. As the speed of the motor A increases in relation to that of the motor B, the output of a speeddifferential sensing device causes closure of contacts 2a of relay 2 whereby contactor Y is changed over. The motor A is by-passed through conductor 11, the effective voltage applied to motor B being reduced by decreasing the pulse rate of semi-conductors in the motor circuit. The contacts 2a re-open when the speeddifferential is reduced, undue frequency of operation of the contacts being prevented by providing the sensor with a wide differential or by using a timing device. When the wheel driven by the motor B leaves the ground, contacts 1a of relay 1 close to energize contactor X. The speed sensor may comprise tachometer generators attached to each armature, or, a relay responsive to the armature voltages. An overide device allows a speed differential when the vehicle is being turned so that the drive to the outer wheel is not removed. Alternatively, the motor driving the inner wheel during turning may be open or short-circuited, or reversed. The back EMF of a run-away motor may be reduced by short-circuiting its armature. The contactors may be replaced by static switches.
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