Permanent Magnet, Direct-Drive Generator
 PacWind's direct-drive generator is integral to the turbine design. The turbine and dual rotor comprise one moving part, as the rotor is attached directly to the turbine. The 27-coil stator is fixed and obviates the need for slip rings.
The output of the generator is low-impedance, 3-phase AC voltage. It varies from 12 VAC at 3 m/s wind velocities to greater than 60 VAC at 15 m/s wind velocities. This output is rectified and the voltage is controlled to 12 VDC in the Voltage Control Circuit. This allows the system to maximize efficiency for charging a12 VDC battery bank as well as provide input to a 12 VDC to 120 VAC, 60 Hz inverter.
The dual rotor contains 36 nickle clad, NdFeB permanent magnets. These powerful magnets have a magnetic field of 1.1 Tesla at their surface. The gap between the magnets and the coils is minimized to reduce drop-off in magnetic field through the coils. The windings and wire gauge are designed to match the impedance with the load of inverter and battery bank.
The generator has an optimum load of 13.5 ohms. Bench tests show a linear increase in voltage with RPM. The driver for the test was a 2 HP (1.5 kW) motor. The voltage curve for the generator is shown here.
Block Diagram for Generator Output Circuit
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