14 May Cooling systems for electric motors
Electric motors are used in machines, processes, and industries all around us. Regardless of the application, managing heat dissipation is a common theme. Electric motors are often selected based upon a particular work or load requirement. When an electric motor is in operation, the rotor and stator losses generate heat which must be managed through an appropriate cooling method.
Right level of cool can mean the difference between keeping things running smoothly or opposite. Efficient cooling has a significant impact on the lifetime of your motor. Maintaining optimal temperature levels are important to avoid efficiency reduction in general. Ensuring proper heat management results in a more reliable and robust motor with a longer lifetime. And with an effective cooling system, it is often possible to use a smaller motor, which carries significant size.
There are many cooling options available for electric motors. The optimal choice depends on your application, where the motor is mounted, the operating environment and several other factors.
The most common type of AC motor is the totally enclosed fan cooled (TEFC) motor, which is provided with an external forced cooling fan mounted on the non-drive end (NDE) of the shaft, with cooling ribs running axially along the outer surface of the motor frame (bidirectional use).
Designation system concerning methods of cooling refers to the standard IEC 60034-6. The most common cooling methods are shown in the table below. Motors are completely closed while cooling is generated through heat transfer over the ribbed housing with fan mounted on the motor shaft on the outside of the motor and protected with a fan cap (IC 411 in acc. with IEC 60034-6). Fan is designed in such a manner that it enables a motor to be loaded with rated parameters regardless of the direction of rotation. Motors must be mounted to enable cooling air to stream around without any obstacle. Incoming air openings on a fan cap must be opened and the distance between the fan cap and obstacle, which can block air entering, must be at least half of motor frame size expressed in mm. Three-phase motors can operate in specific conditions when it is possible to remove the fan and fan cap:
- in a situation when machine has an external ventilation, i.e., motor is in the air stream of an external ventilation adequate or better than its own (IC418). In this case a motor has the same characteristics as a self-ventilated motor.
- for special duty types of motors can be equipped with an independently driven fan (IC416). Such motors are designed on request
IC code vs NEMA designation
In some cases, letter acronyms based on the NEMA (National Electrical Manufacturers Association) definitions are used as an alternative or supplement to the IC code. The IC codes and corresponding NEMA acronyms for the most common methods of cooling are:
IC 411 – Totally Enclosed Fan Cooled (TEFC) – The motor is totally enclosed in a smooth or finned casing and cooled by an external fan mounted on the motor shaft. This is by far the most common of all cooling methods and is used as standard for a wide range of different applications, including pumps, fans, and hydraulics.
IC410 – Totally Enclosed Non-Ventilated (TENV) – The motor is totally enclosed in a smooth or finned casing, without any external fan. This cooling method is especially suitable for winches, cranes and other applications which only operates at constant load for a brief period.
IC416 – Totally Enclosed Force Ventilated (TEFV) – The motor is totally enclosed in a smooth or finned casing and cooled by an externally mounted motorized axial fan supplied with the motor. This method is usually used for applications with VFD controlled motors, which operate at varying speeds or at low speed with constant torque.
IC418 – Totally Enclosed Air Over (TEAO) – The motor is totally enclosed in a smooth or finned casing, without any external fan. Instead, the motor is placed in an airstream generated by the application it powers. This method is often used for fans and especially axial fans or other HVAC applications including cooling towers.
As shown, many cooling methods are especially well suited for specific types of applications. But there are many important elements to consider when choosing how to cool your motor. The optimal cooling strategy depends on your application, the operating environment, lifetime requirements and more. And with insufficient cooling, you could risk burning out the motor windings after only a few minutes of operation in the wrong conditions. To make the right decision, you can rely on Končar-MES to provide advice and support. The technical team has extensive experience and a fully updated overview of the available alternatives and the pros and cons of the individual options.