Switched reluctance motors (SRM)
A magnet-free, simple-rotor design gaining attention as rare-earth costs rise.
You'll learn
- Explain switched reluctance motors (srm) at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real drive unit
Overview
The switched reluctance motor has neither magnets nor rotor windings — it produces torque purely from the tendency of a magnetic circuit to minimise reluctance by pulling iron into alignment.
In depth
An SRM rotor is simply a shaped laminated steel core with salient poles, no windings and no magnets at all. The stator's poles are energised in sequence, and each energised pole pulls the nearest rotor pole into alignment — much like a solenoid pulling in a plunger, repeated around the circumference.
| Property | SRM |
|---|---|
| Magnets | None |
| Rotor windings | None |
| Cost | Low (simple, cheap rotor) |
| Torque ripple | Historically higher, improving with control |
| Fault tolerance | Excellent (phases are independent) |
Key takeaways
Remember this
- SRMs use a simple, unwound, magnet-free rotor and pull iron poles into alignment for torque.
- They avoid rare-earth material entirely, at the cost of higher historic torque ripple and noise.
- Independent stator phases give SRMs excellent fault tolerance.
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