MicroTurbines were first developed for the turbocharger and aircraft industry. As in accessory drives in airplanes, power is generated through a high-speed permanent magnet generator coupled without interfacing circuitry to a mechanical drive. Maintenance free air bearings completely do away with the need for lubricants.
Combustion air enters the MicroTurbine through the generator, cools it in the process and is compressed to about 4 bar in the compressor. Fuel is introduced into the combustion chamber and ignited. Hot combustion gases expand into the turbine and drive the compressor and the generator. Thanks to recuperator technology (preheating of air by hot exhaust gases), electrical efficiencies of 26 to 30% can be achieved.
The permanent magnet is located directly on the drive shaft of the turbine, so that the generator operates at the same rotational speed as the turbine (up to 96,000 rotations per minute). The high-frequency alternating current (1600 Hz) generated is rectified in the turbine’s electronics and its polarity subsequently reversed again to alternating current (50 Hz / 400 V). No autonomous frequency regulation is called for, the desired frequency is delivered by the network. This ensures that the turbine always operates synchronously with the network.