Constant speed drive

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Constant speed drive for Boeing 727, made by Sundstrand Corporation

A constant speed drive (CSD) is a mechanical gearbox that takes an input shaft rotating at a wide range of speeds, delivering this power to an output shaft that rotates at a constant speed, despite the varying input. They are used to drive mechanisms, typically electrical generators, that require a constant input speed. Constant speed drives are usually found as part of the accessory drives of gas turbine engines, such as aircraft jet engines. Constant-speed drives are usually found supplying accessory equipment and are rarely needed for an engine's main power output.

Mechanism[edit]

CSDs are mainly used on airliner and military aircraft jet engines to drive the alternating current (AC) electrical generator. In order to produce the proper voltage at a constant AC frequency, usually three-phase 115 VAC at 400 Hz, a generator needs to spin at a constant specific speed (typically 6,000 RPM for air-cooled generators).[1] Since the jet engine gearbox speed varies from idle to full power, this creates the need for a constant speed drive (CSD). The CSD takes the variable speed output of the accessory drive gearbox and hydro-mechanically produces a constant output RPM.[2][3]

Integrated drive generator[edit]

On aircraft such as the Airbus A310, Airbus A320 family, Airbus A320neo, Airbus A330,[4] Airbus A330neo, Airbus A340,[5] Boeing 737 Next Generation, 747, 757, 767 and 777, an integrated drive generator (IDG) is used.[6] This unit is simply a CSD and an oil cooled generator inside the same case.[7] Troubleshooting is simplified as this unit is the line-replaceable electrical generation unit on the engine.

Manufacturers[edit]

UTC Aerospace Systems (formerly Hamilton Sundstrand) is an American manufacturer of CSD and IDG units.

Alternatives[edit]

A variable-speed constant-frequency (VSCF) generator can be used to provide AC power using an electronic tap converter.

See also[edit]

References[edit]

  1. ^ Carl Tenning. "Designing the 777 Electrical Power System". Retrieved 10 August 2015. 
  2. ^ "CSD". Retrieved 10 August 2015. 
  3. ^ "Constant speed drive – Rolls-Royce Limited". Retrieved 10 August 2015. 
  4. ^ "A330 Electrical". Retrieved 10 August 2015. 
  5. ^ "FCOM A340 Electrical". Retrieved 10 August 2015. 
  6. ^ Pratt & Whitney (August 1988). The Aircraft Gas Turbine Engine and its Operation. P&W Oper. Instr. 200. United Technologies Corporation. pp. 3–45. P&W 182408. 
  7. ^ "Fixed frequency electrical generation system and corresponding control procedure – Airbus France". Retrieved 10 August 2015.