Device and method for estimating internal temperature of electric motor and control device for electric motor

A control device for an electric motor, the electric motor having a stator core extending cylindrically in a direction of an axis and around which a coil is wound, a rotor arranged rotatably around the axis, and a case that houses the stator core and the rotor, the coil being cooled by a first cooling liquid in the case,

• the control device executing an output restriction of the electric motor in case that an internal temperature of the electric motor estimated using a thermal circuit is greater than or equal to a previously defined predetermined judgment temperature, the thermal circuit regarding a temperature of the first cooling liquid after heat reception from the coil as a first temperature equal to a temperature of the case.

A method for estimating an internal temperature of an electric motor, the electric motor having a stator core extending cylindrically in a direction of an axis and around which a coil is wound, a rotor arranged rotatably around the axis, and a case that houses the stator core and the rotor, the coil being cooled by a first cooling liquid in the case, the method comprising:

• estimating the internal temperature by using a thermal circuit that regards a temperature of the first cooling liquid after heat reception from the coil as a first temperature equal to a temperature of the case.

The method for estimating an internal temperature of an electric motor of claim wherein

• the internal temperature is estimated using the thermal circuit with boundary conditions including the first temperature and a second temperature that is at least one of a temperature of the coil, a temperature of the first cooling liquid before heat reception from the coil, and a temperature of a second cooling liquid before heat reception from the first cooling liquid, the second cooling liquid cooling the first cooling liquid.