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 polarity of the voltage on the commutating capacitor, driver operable control means for generating a current demand signal and deriving therefrom upper and lower motor current limits, 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 sensitive to the cessation of flow of current into the commutating capacitor for firing the third thyristor when such current flow ceases, thereby ensuring polarity reversal of the voltage on the commutating capacitor before the next commutation time.
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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 turned off by firing the second thyristor to divert the motor current momentarily into the commutating capacitor. A third thyristor is connected in series with an inductor across the commutating capacitor and serves on firing to reverse the voltage residing on the commutating capacitor following commutation. A circuit is connected to detect the cessation of current flow into the commutating capacitor and acts to fire the third thyristor when such cessation is detected.
9 Citations
7 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 polarity of the voltage on the commutating capacitor, driver operable control means for generating a current demand signal and deriving therefrom upper and lower motor current limits, 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 sensitive to the cessation of flow of current into the commutating capacitor for firing the third thyristor when such current flow ceases, thereby ensuring polarity reversal of the voltage on the commutating capacitor before the next commutation time.
Specification