Importance

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Abstract

An engine cranking motor soft-start system and method includes at least one cranking motor and a switching power converter which is coupled to the cranking motors such that the voltage across the motors varies with the converter's duty cycle. The duty cycle, and thereby the voltage across the motors, is gradually increased over a predetermined period. This serves to limit the acceleration of the cranking motors, and thereby their peak current and torque, which may serve to increase their service life. The cranking motors are typically operatively coupled to drive respective pinion gears which are brought into engagement with a ring gear when starting the engine. The system is preferably arranged such that the gradually increasing duty cycle results in the torque of the cranking motors being sufficient to break an abutment that may be present between the pinion gears and the ring gear.

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First Claim