Electric vehicle traction motor control
First Claim
1. An electric vehicle traction motor control circuit comprising a main thyristor in series with the motor armature between a pair of supply rails, a second thyristor arranged on firing to divert current from the main thyristor into a commutating capacitor, a third thyristor connected in series with an inductor across the commutating capacitor and arranged on firing to reverse the voltage on the commutating capacitor, driver operable control means for determining upper and lower motor current limits, means sensitive to the magnitude of a voltage stored on the commutating capacitor for downwardly adjusting said motor current limits independently of said driver operable control means if said stored voltage is too low to ensure commutation, first firing control means for firing the main thyristor when the actual motor current is less than said lower limit, second firing control means for firing the second thyristor when the actual motor current exceeds the upper limit and third firing control means for the third thyristor.
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Accused Products
Abstract
An electric vehicle traction motor control circuit includes a main thyristor in series with the motor armature. A second thyristor is connected in series with a commutating capacitor across the main thyristor which can be switched off by firing the second thyristor so that the motor current is diverted into the commutating capacitor. A third thyristor is connected in series with an inductor across the commutating capacitor and serves when fired to reverse the voltage residing on the commutating capacitor following commutating. The reversed voltage on the capacitor is detected and is used to control upper and lower current limit signals set by a driver operable control so that the capacitor is not called upon to receive a large current when it is in a low voltage condition.
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Citations
6 Claims
- 1. An electric vehicle traction motor control circuit comprising a main thyristor in series with the motor armature between a pair of supply rails, a second thyristor arranged on firing to divert current from the main thyristor into a commutating capacitor, a third thyristor connected in series with an inductor across the commutating capacitor and arranged on firing to reverse the voltage on the commutating capacitor, driver operable control means for determining upper and lower motor current limits, means sensitive to the magnitude of a voltage stored on the commutating capacitor for downwardly adjusting said motor current limits independently of said driver operable control means if said stored voltage is too low to ensure commutation, first firing control means for firing the main thyristor when the actual motor current is less than said lower limit, second firing control means for firing the second thyristor when the actual motor current exceeds the upper limit and third firing control means for the third thyristor.
Specification