By the term permanent magnet (PM) synchronous generators (SGs), we imply here radial or axial air gap PM brushless generators with distributed (q greater than 1) or concentrated (q ≤ 1) windings & rectangular or sinusoidal current control having surface PM or interior PM (IPM) rotors.
A PMSG’s output voltage amplitude & frequency both are proportional to speed. In case of constant speed prime mover applications, PMSGs might carry out voltage self-regulation by appropriate design; i.e., inset or interior PM pole rotors. Small speed variation (from ±10 to 15%) may be suitable for diode rectified loads with series capacitors & voltage self-regulation. However, the majority applications require operation at variable speed, and, in this case, constant output voltage vs. load, be it direct current (DC) or alternating current (AC), requires full static power conversion & close-loop control.
The Versatile mobile generator sets (gen-sets) employ variable speed for fuel savings, & PMSGs by means of full power electronics control can provide high torque density, low losses, & multiple outputs (DC and AC at fifty [60] Hz or 400 Hz, single phase or 3 phase).
A high efficiency, high active power to max out kilovolt ampere (kVA) ratio permits for reasonable power converter costs that offset the additional costs of PMs as compared to SRGs (switched reluctance generators) or induction generators (IGs) for the same level of speed.
Fly-wheel batteries with high kilowatts per kilogram (kW/kg), good kilo-watt hours per kilogram (kWh/kg), & long life, also utilize super-high-speed PMSGs with 4-quadrant P & Q control. They are proposed for energy storage on vehicles & spacecraft & for power systems backup.
Diverse as they may appear, these applications are accommodated by only a small number of practical PMSGs classified as follows:
1. With radial airgap (cylindrical rotor)
2. With axial airgap (disk rotor)
3. With distributed stator windings (q > 1)
4. With concentrated windings (q ≤ 1)
5. With surface PM rotors
6. With interior or inset PM rotors
7. With rectangular current control
8. With sinusoidal current control
9. In terms of loads, they are classified as follows:
10. With passive AC load
11. With DC load
12. With controlled AC voltage and frequency at variable speed
The super-high-speed PM generators are different in rotor construction, which requires a mechanical shell against centrifugal forces & a copper shield (damper) for reducing rotor losses. Also, at high fundamental frequency (above 1 kHz), stator skin effect & control imply special solutions for reducing machine & static converter losses & overall costs. As in nearly all PMSG surfaces PM rotors are used, the latter will be provided the most attention.
A full analytical field model is introduced & thoroughly checked through finite element method (FEM) field and torque production analysis. Loss models for generator steady-state circuit modeling are brought in for rectangular & for sinusoidal current control.
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