ELECTRIC POWER STEERING SYSTEM

PROBLEM TO BE SOLVED: To set the optimal steering assist amount taking the relation of the real power consuming amount of a steering assist motor and the power load of a vehicle after idle-stop condition is established into consideration.SOLUTION: An inverter energy consumption calculation unit 37 estimates the actual power consumption of a steering operation assist motor 3 after an engine is placed in an idle-stop state, and a command value of current to be supplied to the steering operation assist motor 3 is limited such that the command value is smaller as the energy consumption is larger. The inverter energy consumption calculation unit 37 calculates the energy consumption of an inverter drive circuit 12 by integrating an amount of electric power consumed by the inverter drive circuit 12. The optimal steering assist amount can be set while protecting the power source 30 from overload during the idle-stop.