In the actual working process of the motor, there will be short-term overload conditions, which puts forward higher requirements for maintaining the overload capacity of the motor. Due to the limitation of the thermal limit on the overload capacity of the motor, taking a 250kW permanent magnet synchronous motor (PMSM) as an example, this paper proposes a thermal management scheme of companion-type direct cooling, and establishes a three-dimensional thermal network model considering the secondary circulation factor. At the same time, in order to explore the influence of the thermal management scheme on the overload capacity of the motor when there is an impact load, on the premise that there is a safety margin for the hottest spot temperature of the winding under the rated state of the motor, the impact load is simulated by setting the overload torque, the thermal network model is used to compare and analyze the temperature field of the motor based on the companion-type direct cooling and the indirect casing cooling, and combining with the insulation limit to quantitatively compare the overload capacity of the motor after impact load. Through the simulation test, it is verified that the motor based on the companiontype direct cooling has efficient heat dissipation and stronger impact-resistance overload capability. The proposal of the companion-type direct cooling scheme has important practical significance for excavating the load potential of the motor under actual operating conditions.INDEX TERMS companion-type direct cooling, secondary circulation, high-precision three-dimensional thermal network, impact load, evaluation of overload capacity, simulation test.

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