| 摘要 |
676,049. Control of motors. BRITISH THOMSON-HOUSTON CO., Ltd. June 14, 1950. [June 14, 1949] No. 14869/50. Class 38, (iii). Means for indicating or restricting the speed of an electric motor, in the event of wheelslip, for example, when the motor is used for traction, comprises a relay having a magnetic core 9 excited by opposing windings 10 and 12. The winding 10 is energized in accordance with the voltage across the armature 1 of the motor and has an adjustable resistor 11 connected in series with it. The winding 12 is connected in series with the motor field winding 8 and together with this winding in parallel to resistor 5, or is connected across a resistor which is in series with winding 8 and, with it, across resistor 5. A pivoted, spring- biased, armature 13 is formed as a permanent magnet or is polarized by a coil fed from a constant source, and, when the motor speed is below a pre-determined value, the armature occupies the position shown. When the motor speed exceeds the set value the polarity of the core 9 is reversed and the armature is moved to open contacts 15, 16, and close contacts 15, 17, so energizing means for indicating or remedying the condition. The relay may have a third winding supplied through contacts 15, 17, to hold the relay in its released condition until re-set by de-energizing the holding coil. In a modified form the relay is of the balance type, the coils 10 and 12 co-operating with cores fixed to the ends of a lever which is pivoted at its centre, Fig. 3 (not shown). In a further modification the relay-coils are mounted co-axially, Fig. 4 (not shown). If the motor has no winding compensating for armature reaction, a compensating coil may be provided on the relay. This additional coil is energized in accordance with the motor armature current and opposes the relay-coil energized in accordance with the motor field current. When the system has several motors, a relay is provided for each motor, and the several relays may have parts in common. If the motor is of the compound type the relay may have in addition, a coil energized in accordance with the shunt field current.
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