What are the main sources of losses and noise in PMSMs and how can you reduce them?

1 Copper losses

Copper losses are the power dissipated as heat due to the resistance of the windings and the current flowing through them. Copper losses depend on the square of the current and the winding resistance, which increases with temperature. To reduce copper losses, you can use thicker wires, optimize the winding configuration, and improve the cooling system of the motor.

2 Iron losses

Iron losses are the power dissipated as heat due to the alternating magnetic fields in the stator and rotor cores. Iron losses consist of hysteresis losses and eddy current losses. Hysteresis losses are caused by the repeated magnetization and demagnetization of the core material, while eddy current losses are caused by the induced currents in the core due to the changing magnetic flux. To reduce iron losses, you can use high-quality core materials with low hysteresis and high resistivity, reduce the air gap, and minimize the harmonic content of the current and voltage.

3 Mechanical losses

Mechanical losses are the power dissipated as heat due to the friction and windage of the rotating parts of the motor. Mechanical losses include bearing losses, fan losses, and seal losses. Bearing losses are caused by the friction and lubrication of the bearings that support the rotor shaft, fan losses are caused by the air drag of the cooling fan attached to the shaft, and seal losses are caused by the friction of the seals that prevent fluid leakage. To reduce mechanical losses, you can use high-quality bearings, optimize the fan design and size, and avoid excessive seal pressure.

4 Noise and vibration

Noise and vibration are the undesirable acoustic and mechanical effects of the motor operation. Noise and vibration are mainly caused by the electromagnetic forces acting on the stator and rotor teeth, the torque ripple due to the non-uniform air gap and current waveform, and the mechanical imbalance and misalignment of the rotor shaft. Noise and vibration can affect the user comfort, the structural integrity, and the acoustic emissions of the motor. To reduce noise and vibration, you can use skewing, slotting, or shaping techniques to reduce the cogging torque and the electromagnetic forces, use sinusoidal or vector control methods to reduce the torque ripple and harmonics, and balance and align the rotor shaft and bearings.

5 Demagnetization losses

Demagnetization losses are the power dissipated as heat due to the irreversible reduction of the magnetization of the permanent magnets in the rotor. Demagnetization losses are caused by high temperatures, high currents, or external magnetic fields that exceed the coercivity of the magnet material. Demagnetization losses can affect the torque and efficiency of the motor, as well as the magnetic circuit design. To reduce demagnetization losses, you can use high-coercivity magnet materials, avoid overheating and overloading the motor, and shield the rotor from external magnetic fields.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?