Constant speed drive

Last updated

Constant speed drive for Boeing 727, made by Sundstrand Corporation Constant Speed Drive for Boeing 727, Sundstrand Corporation - Museum of Science and Industry (Chicago) - DSC06323.JPG
Constant speed drive for Boeing 727, made by Sundstrand Corporation

A constant speed drive (CSD) is a type of transmission 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.

Contents

The term is most commonly applied to hydraulic transmissions found on the accessory drives of gas turbine engines, such as aircraft jet engines. On modern aircraft, the CSD is often combined with a generator into a single unit known as an integrated drive generator (IDG).

Mechanism

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, an alternator 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]

Different systems have been used to control the alternator speed. Modern designs are mostly hydrokinetic, but early designs often took advantage of the bleed air available from the engines. Some of these were mostly mechanically powered, with an air turbine to provide a vernier speed adjustment. Others were purely turbine-driven. [4]

Integrated drive generator

On aircraft such as the Airbus A310, Airbus A320 family, Airbus A320neo, Airbus A330, [5] Airbus A330neo, Airbus A340, [6] Boeing 737 Next Generation, 747, 757, 767 and 777, an integrated drive generator (IDG) is used. [7] This unit is simply a CSD and an oil cooled generator inside the same case. [8] Troubleshooting is simplified as this unit is the line-replaceable electrical generation unit on the engine.

Manufacturers

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

Alternatives

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

Variable Frequency Starter Generator (VFSG) used primarily on the Boeing 787 are both used for electric start and electric generation.

See also

Related Research Articles

Gas turbine Type of internal combustion engine

A gas turbine, also called a combustion turbine, is a type of continuous and internal combustion engine. The main elements common to all gas turbine engines are:

Electric generator Device that converts other energy to electrical energy

In electricity generation, a generator is a device that converts motive power into electrical power for use in an external circuit. Sources of mechanical energy include steam turbines, gas turbines, water turbines, internal combustion engines, wind turbines and even hand cranks. The first electromagnetic generator, the Faraday disk, was invented in 1831 by British scientist Michael Faraday. Generators provide nearly all of the power for electric power grids.

Power supply

A power supply is an electrical device that supplies electric power to an electrical load. The primary function of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a result, power supplies are sometimes referred to as electric power converters. Some power supplies are separate standalone pieces of equipment, while others are built into the load appliances that they power. Examples of the latter include power supplies found in desktop computers and consumer electronics devices. Other functions that power supplies may perform include limiting the current drawn by the load to safe levels, shutting off the current in the event of an electrical fault, power conditioning to prevent electronic noise or voltage surges on the input from reaching the load, power-factor correction, and storing energy so it can continue to power the load in the event of a temporary interruption in the source power.

Alternator Electromechanical device that converts mechanical energy to electrical energy in the form of alternating current

An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature. Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines.

A governor, or speed limiter or controller, is a device used to measure and regulate the speed of a machine, such as an engine.

Transmission (mechanics)

A transmission is a machine in a power transmission system, which provides controlled application of power. Often the term 5-speed transmission refers simply to the gearbox, that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device.

Continuously variable transmission Automatic transmission that can change seamlessly through a continuous range of effective gear ratios

A continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM while the vehicle moves at varying speeds.

Turboshaft Gas turbine used to spin a shaft

A turboshaft engine is a form of gas turbine that is optimized to produce shaftpower rather than jet thrust. In concept, turboshaft engines are very similar to turbojets, with additional turbine expansion to extract heat energy from the exhaust and convert it into output shaft power. They are even more similar to turboprops, with only minor differences, and a single engine is often sold in both forms.

Motor–generator

A motor–generator is a device for converting electrical power to another form. Motor–generator sets are used to convert frequency, voltage, or phase of power. They may also be used to isolate electrical loads from the electrical power supply line. Large motor–generators were widely used to convert industrial amounts of power while smaller motor–generators were used to convert battery power to higher DC voltages.

Motor drive

Motor drive, or simply known as drive, describes equipment used to control the speed of machinery. Many industrial processes such as assembly lines must operate at different speeds for different products. Where process conditions demand adjustment of flow from a pump or fan, varying the speed of the drive may save energy compared with other techniques for flow control.

Diesel generator

A diesel generator (DG) is the combination of a diesel engine with an electric generator to generate electrical energy. This is a specific case of engine-generator. A diesel compression-ignition engine is usually designed to run on diesel fuel, but some types are adapted for other liquid fuels or natural gas.

Free-piston engine

A free-piston engine is a linear, 'crankless' internal combustion engine, in which the piston motion is not controlled by a crankshaft but determined by the interaction of forces from the combustion chamber gases, a rebound device and a load device.

Droop speed control is a control mode used for AC electrical power generators, whereby the power output of a generator reduces as the line frequency increases. It is commonly used as the speed control mode of the governor of a prime mover driving a synchronous generator connected to an electrical grid. It works by controlling the rate of power produced by the prime mover according to the grid frequency. With droop speed control, when the grid is operating at maximum operating frequency, the prime mover's power is reduced to zero, and when the grid is at minimum operating frequency, the power is set to 100%, and intermediate values at other operating frequencies.

Magneto Electricity-producing machine

A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, although it is usually considered distinct from most other alternators, which use field coils rather than permanent magnets.

Flux switching alternator

A flux switching alternator is a form of high-speed alternator, an AC electrical generator, intended for direct drive by a turbine. They are simple in design with the rotor containing no coils or magnets, making them rugged and capable of high rotation speeds. This makes them suitable for their only widespread use, in guided missiles.

Automatic generation control

In an electric power system, automatic generation control (AGC) is a system for adjusting the power output of multiple generators at different power plants, in response to changes in the load. Since a power grid requires that generation and load closely balance moment by moment, frequent adjustments to the output of generators are necessary. The balance can be judged by measuring the system frequency; if it is increasing, more power is being generated than used, which causes all the machines in the system to accelerate. If the system frequency is decreasing, more load is on the system than the instantaneous generation can provide, which causes all generators to slow down.

Accessory drive

The accessory drive is a gearbox that forms part of a gas turbine engine. Although not part of the engine's core, it drives the accessories, fuel pumps etc., that are otherwise essential for the operation of the engine or the aircraft on which it is mounted. Accessory drives on large engines handle between 400–500 hp.

Single-phase generator

Single-phase generator is an alternating current electrical generator that produces a single, continuously alternating voltage. Single-phase generators can be used to generate power in single-phase electric power systems. However, polyphase generators are generally used to deliver power in three-phase distribution system and the current is converted to single-phase near the single-phase loads instead. Therefore, single-phase generators are found in applications that are most often used when the loads being driven are relatively light, and not connected to a three-phase distribution, for instance, portable engine-generators. Larger single-phase generators are also used in special applications such as single-phase traction power for railway electrification systems.

Most of the terms listed in Wikipedia glossaries are already defined and explained within Wikipedia itself. However, glossaries like this one are useful for looking up, comparing and reviewing large numbers of terms together. You can help enhance this page by adding new terms or writing definitions for existing ones.

Internal combustion locomotive Railway locomotive that produces its pulling power through an internal combustion engine

An internal combustion locomotive is a type of railway locomotive that produces its pulling power using an internal combustion engine. These locomotives are fuelled by burning fossil fuels, most commonly oil or gasoline, to produce rotational power which is transmitted to the locomotive's driving wheels by various direct or indirect transmission mechanisms. The fuel is carried on the locomotive.

References

  1. Carl Tenning. "Designing the 777 Electrical Power System" . Retrieved 10 August 2015.
  2. "CSD". Archived from the original on 31 July 2010. Retrieved 10 August 2015.
  3. "Constant speed drive – Rolls-Royce Limited" . Retrieved 10 August 2015.
  4. "Accessory Power – Constant speed drives and starters". Flight International : 460–461. 16 September 1960.
  5. "A330 Electrical" . Retrieved 10 August 2015.
  6. "FCOM A340 Electrical" . Retrieved 10 August 2015.
  7. 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.
  8. "Fixed frequency electrical generation system and corresponding control procedure – Airbus France" . Retrieved 10 August 2015.