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Constant speed drive (CSD)
  • CSD is a hydromechanical unit that is installed in between engine and generator. The basic purpose to provide constant frequency output.
  • A constant speed drive (CSD) which convert the variable speed of a jet engine into a constant speed to drive a 400Hz constant frequency electric generator to provide power for an aircraft's electrical system. A special drive system used to connect an alternating current generator to an aircraft engine. The drive holds the generator speed (and thus its frequency) constant as the engine speed varies.
  • Constant-speed drive. A component used with either aircraft gas turbine or reciprocating engines to drive AC generators. The speed of the output shaft of the CSD is held constant while the speed of its input shaft caries. The CSD holds the speed of the generator, and the frequency of the AC constant as the engine speed varies through its normal operating range.
Integrated Drive Generator (IDG)
  • The IDG(Integrated Drive Generator) is an aircraft power generation device that houses a Continuously Variable Transmission(CVT) to generate 400Hz constant frequency power regardless of the engine speed.
  • No alt text provided for this image An AC generator installed on turbine engines. An IDG incorporates a brush-less, three-phase AC generator and a constant-speed drive in a single component. The main source of A.C. (alternating current) electrical power on the aircraft; it is a combination of a constant speed drive and an electrical generator driven by the engine through the accessory gearbox.
  • The integrated drive generator (IDG) consists of a Constant Speed Drive (CSD) and AC generator mounted side by side in a single housing. The CSD performs the operation by controlled differential action to maintain the constant output speed required to drive the generator
Variable Frequency Generators (VFG)
  • Variable-Frequency Generator (VFG), was designed and built with the capabilities of starting large motors and of operating them at variable speed and voltage. No alt text provided for this image How does a variable speed generator work?
  • The output power of a variable speed generator depends directly on the speed of the motor. When the motor speed is too low for the power demand, the output voltage of the generator is decreased. No alt text provided for this image.
  •  To correctly check the oil level the CSD/IDG must first be vented for 15 seconds to release pressure. Caution: a spray of hot oil can emit from the vent during this process. The vent on the IDG is at the top of the sight glass To keep a constant frequency of 400 Hz, most aircraft have a CSD (Constant Speed Drive) associated with the AC generator. On most types (e.g. A320, A330, B737, B747, B777) an Integrated Drive Generator (IDG) is used. This unit is simply a CSD and an oil-cooled generator inside the same case that provides this fixed frequency output. The A380 and A350 have a variable-frequency electrical generator, with no CSD or IDG.
credit by chhawinder pal 

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  1. Hi ! How are you ??
    As concern of VFG installed on C_130 Aircraft it is very reliable ,it gives out put with tolerance of frequency from 380 HZ to 420 HZ . With this type Generator AC Control panel and voltage regulator ,FSR used Initially when Engine start PMG generate voltage which is feed to Voltage regulator than Voltage regulator step down AC power and converted to DC Voltage and again supply to main stator than stator generates out put 115 VAC .


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