Cooling systems for motors
Water jackets, oil spray and how heat actually leaves a compact traction motor.
You'll learn
- Explain cooling systems for motors at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real drive unit
Overview
A modern traction motor packs tens of kilowatts of loss into a housing the size of a large saucepan — cooling it effectively is what allows continuous power ratings to approach peak figures.
In depth
Motor explorer
Cooling system explorer
Switch to the cooling view to see the jacket surrounding the stator.
Cooling · 1 components
| Cooling method | Removes heat from | Typical use |
|---|---|---|
| Water-glycol jacket | Stator housing | Most production EV motors |
| Direct oil spray on end windings | Copper end-turns directly | High power-density performance motors |
| Rotor oil-through-shaft cooling | Rotor and magnets | Very high continuous power designs |
Calculator
Cooling Requirement Calculator
Coolant flow needed to hold a component at a target temperature.
kW
K
kJ/kg·K
°C
Required mass flow
0.29kg/s
Required flow
16.2L/min
Radiator duty at 40 °C coolant
6.0kW
Formula
ṁ = Q ÷ (c_p × ΔT_allowed)Rearranging the heat equation gives the mass flow required to carry away a known heat load within an allowed temperature rise. The radiator must then reject that same heat to ambient air.
Example: 6 kW with a 6 K allowed rise in glycol needs about 0.29 kg/s of flow.
- Radiator capacity falls sharply as ambient temperature approaches coolant temperature.
- Chillers borrow the refrigerant loop when the radiator alone cannot cope.
- Flow beyond about 0.5 kg/s per loop gives diminishing returns for large pump cost.
Key takeaways
Remember this
- Water-glycol jackets around the stator are the most common cooling approach.
- Direct oil spray targets the end windings, often the hottest point in the motor.
- Cooling capability directly sets how close continuous power can get to peak power.
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