The rotor in detail
Interior magnets, surface magnets, squirrel cages — how rotors differ and why.
- Explain the rotor in detail at engineering level
- Read the numbers that define the behaviour
- Apply the idea to a real drive unit
Overview
The rotor carries the field (or the induced current) that the stator's rotating field pulls along — and its exact construction is one of the biggest differences between motor types.
In depth
Rotor explorer
Switch to the rotor view and inspect the magnets and shaft.
Interior vs surface-mounted magnets
Interior permanent magnet (IPM) rotors bury magnets inside slots in the steel, protecting them mechanically and adding a second torque source called reluctance torque from the asymmetric magnetic path. Surface-mounted magnet (SPM) rotors glue magnets to the rotor's outside, giving a simpler, cheaper build but more exposure to demagnetisation and higher-speed retention challenges.
Key takeaways
- The rotor's construction differs sharply between IPM, SPM and induction designs.
- Interior magnets are protected and add reluctance torque but cost more to manufacture.
- Surface magnets are simpler but need retention sleeves at high speed.
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