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Pub. No.:    WO/2014/195706    International Application No.:    PCT/GB2014/051730
Publication Date: Fri Dec 12 00:59:59 CET 2014 International Filing Date: Thu Jun 05 01:59:59 CEST 2014
IPC: H02P 29/02
B62D 5/04
H02P 21/00
Applicants: TRW LIMITED
Inventors: SCOTSON, Peter Geoffrey
A motor control circuit for an electric motor of an electric power assisted steering system comprises a switching circuit comprising a plurality of electrical switches, a current demand signal generator which converts the torque demand signal into a current demands signal;and a fault mode motor current controller that is responsive to an error signal that represents the difference between the current demand signal and the actual current flowing in the motor and is operable in the event of a fault where one phase is open-circuit to drive the remaining two phases as a single combined phase by generating a single voltage demand signal that is representative of the voltage to be applied across the combined phases, the voltage signal being in turn fed into a drive circuit for the switches that generates pulse width modulated switching signals for the switching circuit required to apply the voltage across the combined phases.