As the output of DC motors for electrical power steering becomes higher, noise reduction and temperature rise reduction are increasingly demanded. We previously proposed the short circuit wires is symmetrical position and realized a noise reduction, but the characteristics of the motor are affected by the resistance of the short circuit wires. Therefore, we then examine the relationship between the resistance of the short circuit wires and the brush current and the winding current in detail. As a result, it was proven that the level of the exciting force is large when the resistance is large, and that the maximum value of the brush temperature rise is large when the resistance is small. And we propose a brush current control method which minimizes the maximum value of the brush temperature rise. As a result, by controlling the electric power consumption of a homopolar brush equally, we can decrease the maximum value of the brush temperature rise.
