Abstract: A fail-safe arrangement for an electrical power steering system is directed to providing a control arrangement for a power steering motor which will prevent abnormal operation from having adverse impact. The control system detects the welding or sticking together of closed relay contacs and functions to prevent such a situation by monitoring the motor terminal voltage so as to cut off power above a predetermined value regardless of position of the relay contacts.

Abstract: The current limiter for an electrical actuator includes a switch for selectively controlling the current supplied to the electrical actuator. A detector detects the current level flowing through the electrical actuator and an electronic controller adjusts the duty ratio for the switch in order to limit excessive current. The electronic controller includes a comparator for comparing the current through the electrical actuator with an upper threshold level and a lower threshold level. The duty ratio is decreased gradually if the current exceeds the upper threshold level and is gradually increased if the current is below the lower threshold level. The duty ratio is sustained if the current is a range between the upper and lower threshold levels.