Electric motors are used in machines and processes all around us. You can find them in factories, automobiles, airplanes, robots and even your favorite DVD vending machine. Regardless of the application, managing heat dissipation is a common theme. Electric motors are often selected based upon a particular work or load requirement. One consideration of this selection process is managing heat dissipation. Although electric motor design is constantly improving, all generate heat through losses and inefficiencies. This needs to be evaluated when selecting the proper motor for your needs.
In most cases, heat dissipation is achieved through conductive cooling. In this method heat is transferred from the motor through the mounting interface into the machine structure. Motor manufacturers will often note a heat sink size on their data sheets. This heat sink size is used to determine the continuous torque capability of the motor. If more or less heat dissipation is available, the motor's load capability is increased or decreased. The Kollmorgen AKM Servo Motor shown above uses conductive cooling.
Another method to remove heat from electric motors is by providing forced air cooling. This is commonly done by providing an electric fan to blow air over the motor. Force air cooling can reduce the amount of heat transferred into the machine structure and allow the motor to be operated at a higher load point. A foot mounted PMDC (permanent magnet direct current) motor with air over cooling (TEFC) is shown above.
Liquid cooling can also be used to dissipate heat from an electric motor. With liquid cooling ethylene glycol or other liquid cooling agent is circulated in or around the motor housing or coils to dissipate heat. This would be similar to the radiator system on an automobile engine. The motor above is a custom water cooled design by Kollmorgen.
Although heat dissipation is not always a top criteria for electric motor selection it should be considered as part of the overall machine build. Some motors can be located on a machine where excess heat could cause burns to users. Thermal expansion caused by heating of a machine structure could cause process issues and under sizing or ignoring motor heat dissipation could result in product failure.