The hydrodynamic integrated drive generator (IDG) comprises the adjustable hydrodynamic torque converter and fixed frequency three-phase AC generator, 400+2 % Hz, with 208/120 V nominal voltage, integrated in one unit.
The adjustable hydrodynamic torque converter, which pump wheel is driven by the engine gearbox, provides power transmission due to hydrodynamic forces of working fluid (fuel) supplied by the centrifugal pump to the turbine wheel mounted on the shaft of AC generator rotor.
The unit is cooled by pumping working fluid (fuel) through its cavities.
The working fluid is supplied to the IDG by a centrifugal engine driven pump (CEDP) and discharged to the inlet of CEDP or partly into the fuel tank. Vanes with turning gear are installed in the working fluid flow path of a hydrodynamic converter sporting original geometry of flow cavities; by means of these guide vanes, the generator speed is sustained through the unit control system, and consequently, the frequency of electric current is kept within the prescribed limits. The control system comprises the centrifugal governor, vane adjusting mechanism and electronic control module.
It should be especially remarked that IDGs of the PGL type by mass, dimensions, manufacturability and cost surpass other types of IDGs used in aviation AC fixed frequency electric systems and are highly competitive in terms of reliability and operational life.
The PGL-21, PGL-40, PGL-80 and PGL-130 IDGs developed according to this schematic and their modifications with a capacity from 15 to 80 кVА with excellent energy and mass characteristics are used successfully in MIG-29, YAK-130 and some other aircraft, including Chinese fighter airplanes.
Latest development in this field by Kristall Design Bureau – a dual-mode IDG with a capability to start-up the engine. It features a permanent magnet generator, which can work as a motor, and two hydraulic couplings, one that provides constant rpm in generator mode, and the second one that transmits torque from the generator/motor to the engine gearbox in starter mode. This IDG has an excellent weight-to-power ratio of 0,3 kg/kW and has virtually unlimited power transmission capacity, with current prototypes handling up to 250 kW of power.