Safe driving
07 April 2009
CW relay for electrically powered steering systems adds safety to cars.
Electrically Powered Steering (EPS) is expected to gradually replace conventional hydraulic power steering, making the hydraulic pump redundant. Not only is the car’s weight reduced, EPS systems improve fuel efficiency and minimise carbon dioxide emissions.
In addition, the versatility of an electronic system opens new roads to optimising steering assistance, e.g. by adjusting the behaviour of the steering under various driving conditions, or with automatic parking assistance. EPS is becoming increasingly popular in state-of-the-art vehicles with combustion engines, but for the automobiles of tomorrow, i.e. hybrid and electric vehicles, EPS is the only answer.
If the steering system malfunctions, the relay disconnects the EPS motor, reverting to manual steering and making the system safe. For EPS, a Y circuit is generally used to connect a 3-phase asynchronous motor. One approach to stop the motor is for a relay to open the circuit by disconnecting all 3 phases at once. However, the CW relay distinguishes itself by disconnecting only 2 phases. This solution also stops the motor, but it offers certain advantages: the relay can be mounted away from the motor where the ambient temperature is lower, which extends the components’ lifetime.
Able to disconnect 200 A, the CW relay can be used in EPS applications for heavy cars and SUVs where steering forces are high. Currently the CW relay has terminals for welding assembly, but a version for PCB mounting will be available soon.
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