Tech Torqs #12: How Does Rotor Temperature Affect Permanent Magnet Motors?
Rotor temperature directly impacts magnetic strength in permanent magnet motors. As magnets heat up, torque constant decreases and current demand increases - and excessive heat can cause irreversible demagnetization. Proper thermal management is essential for maintaining torque motor performance and reliability.
February 25, 2026
In permanent magnet motors, most electrical losses occur in the stator. However, that doesn’t mean the rotor is immune to heat.
Over time, small rotor losses combined with heat transfer from the stator can increase rotor temperature. And when rotor temperature rises, it directly affects the motor’s magnetic strength.
Permanent magnets weaken as they get hotter - typically by about 1% per 10°C.
- A weaker magnetic field leads to:
- A reduced torque constant
- Higher current required for the same torque
- Increased losses
- Reduced achievable torque at current limits
If temperatures rise too far, permanent magnets can begin to demagnetize. Unlike normal thermal effects, demagnetization is irreversible. Once it happens, the motor’s performance is permanently reduced.
This is why rotor temperature management is critical in permanent magnet motors - especially in high-performance torque motor applications.
If you have a question about motors or motion systems, share it in the comments on our LinkedIn post or send it to us directly - we might feature it in the next Tech Torqs episode.
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