What are the key design considerations for permanent magnet machines?

PM machine design involves: magnet selection (NdFeB for high performance, ferrite for cost), demagnetization analysis (ensure operating point above knee in worst-case), cogging torque minimization (skewing, magnet shaping, slot/pole combination), back-EMF waveform shaping, eddy current losses in magnets and rotor, thermal management (magnets lose strength at high temperature), and mechanical retention (especially at high speed). IPM versus SPM topology selection affects flux weakening capability, inductance, and efficiency at different operating points.