Thermal Design of an Integrated Motor Drive

A drive based on a matrix power converter for a 30kW totally enclosed, fan cooled induction motor was developed to be fully integrated within the spatial envelope of the motor, located inside the end cover at the fan end of the machine. This paper describes the thermal design of the motor to dissipate the losses from the drive, which were approximately a third of those from the motor. The power electronic components were mounted on the inside of a new end cover which was equipped with an extensive array of fins cooled by air from the external fan. The electronic components were insulated from the air in the end region of the motor. A heat sink plate was installed within the motor behind the end cover to conduct the heat from the motor that would otherwise have been dissipated through the end cover. Computational fluid dynamics (CFD) was used to model the ventilation and heat transfer from the new end cover and to develop improved fan geometries. It was concluded that CFD can be used effectively to design motor cooling systems. An improved fan geometry was designed to keep the power electronics cool under high ambient temperatures with the motor running at full load.