Permanent magnet synchronous motors (PMSM)
The most common EV traction motor type, and why it dominates the market.
- Explain permanent magnet synchronous motors (pmsm) at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real drive unit
Overview
The permanent magnet synchronous motor, PMSM, is the workhorse of the modern EV industry, chosen for its high efficiency and torque density.
In depth
A PMSM's rotor carries permanent magnets rather than induced currents, so the rotor turns in exact lockstep — synchronously — with the stator's rotating field, with zero slip. Because the magnets provide the field for free, PMSMs achieve very high efficiency across a wide operating range, and their compact rotor gives excellent torque density.
| Property | Typical PMSM figure |
|---|---|
| Peak efficiency | 96-97% |
| Torque density | High |
| Rare-earth magnet content | Significant (Nd-Fe-B) |
| Cost driver | Magnet material price |
PMSM cost and supply chain are exposed to neodymium and dysprosium pricing and geopolitics, motivating research into reduced- or no-rare-earth alternatives.
Key takeaways
- PMSMs use rotor magnets and run with zero slip relative to the stator field.
- They offer very high efficiency and torque density, dominating current EV designs.
- Their main drawback is dependence on rare-earth magnet materials.
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