Advantage:

• No excitation winding, magnetizing exciter,AVR, etc. Efficiency and power factor higher 20% than common excitation generator.
• It can load inductive load of 80% self-capacity like as UPS, air condition unit,electric motor, etc. however, common generator usually under 34%.
• High reliability ? simple maintenance and operation
• High power density, high voltage stability for shock load
  Voltage fluctuation ratio less than 0.5%, waveform distortion ratio less than 2%, can used for precision instrument and meter, etc.
  Wave compare:
  
  Output wave for rare-earth permanent magnet alternator
  
  output wave for common alternator with AVR