SERVICE
What are the common cooling methods used for electric motors?
During energy conversion, an electric motor incurs certain losses that are dissipated as heat. This heat must be continuously removed through the motor’s housing and the surrounding medium; this heat‑dissipation process is referred to as cooling.
The designation for motor cooling methods consists primarily of the cooling method code (IC), the circuit arrangement code for the cooling medium, the cooling medium code, and the drive method code for the cooling medium’s circulation.
“IC + Circuit Layout Code + Cooling Medium Code + Propulsion Method Code”
IC – The cooling method code is an abbreviation of the English term “International Cooling.”
Coolant circuit arrangement codes—represented by characteristic digits—are primarily 0, 4, 6, and 8. Their specific meanings are shown in the table below.
| Characteristic number | Meaning | Brief description |
|---|---|---|
| 0 | The cooling medium is directly and freely drawn from the surrounding environment and then returned directly to it (open circuit). | Free circulation |
| 4 | The primary cooling medium circulates within a closed loop inside the motor and transfers heat to the surrounding ambient medium via the housing surface. The housing surface may be smooth or finned, and an external shroud may be employed to enhance heat transfer performance. | Case surface cooling |
| 6 | The primary cooling medium circulates within a closed loop and transfers heat to the surrounding ambient medium via an external cooler mounted on the motor. | External Cooler (using the surrounding environmental medium) |
| 8 | The primary cooling medium circulates within a closed loop and transfers heat to a remote medium via an external cooler mounted on the motor. | External Cooler (Using a distant medium) |
The designations for cooling media are as follows:
| Cooling medium | Feature code |
|---|---|
| Air | A |
| Hydrogen gas | H |
| Nitrogen gas | N |
| Carbon dioxide | C |
| Water | W |
| oil | U |
If the cooling medium is air, the letter A denoting it may be omitted; in practice, the cooling medium we use is almost always air.
The commonly used methods for driving the circulation of the cooling medium are as follows:
| Characteristic number | Meaning | Brief description |
|---|---|---|
| 0 | Driving the circulation of the cooling medium by means of a temperature difference. | Free convection |
| 1 | The motion of the cooling medium is related to the motor speed; it may be driven by the rotor itself, or by an integral fan or pump coupled to the rotor, thereby inducing fluid circulation. | Self-circulation |
| 6 | The medium is driven by an independent component mounted on the electric motor, whose power requirement is independent of the host machine’s rotational speed—for example, backpack blowers or fans. | Externally mounted independent component drive |
| 7 | Independent electrical or mechanical components, installed separately from the electric motor, drive the coolant flow, or rely on the pressure within the coolant circulation system to propel the coolant. | Modular independent component drive |
For example, the commonly used IC0411 is a totally enclosed, self‑ventilated motor with a finned housing; its internal and external airflows are circulated by an integral fan.
