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Wind turbines use different generator designs, depending on the turbine and how it connects to the electricity grid. Common systems include induction generators, doubly fed induction generators (DFIGs) and synchronous generators, such as permanent magnet synchronous generators (PMSGs).
The generator is one part of a larger system. The drivetrain, power converter and control equipment also affect how the turbine produces electricity.
Wind turns the turbine blades and rotor, which drive a generator. The generator converts that mechanical rotation into electrical energy.
Wind speed changes, so a turbine’s rotational speed and electrical output can vary. Its electrical system manages that output and prepares it for connection to the grid. The exact arrangement depends on the turbine model and its operating requirements.
|
Generator type |
How it works |
Typical use and considerations |
|
Squirrel-cage induction generator |
Uses an induction machine with a squirrel-cage rotor. It needs reactive power to create its magnetic field. |
Used in some fixed-speed and older turbine systems. Reactive power must come from the grid or suitable compensation equipment. |
|
Doubly fed induction generator (DFIG) |
Uses a wound-rotor induction machine. Its stator connects to the grid and its rotor connects to a partial-scale power converter. |
Allows variable-speed operation over a range. The converter and rotor form part of the turbine’s electrical control system. |
|
Permanent magnet synchronous generator (PMSG) |
Uses permanent magnets to create the rotor’s magnetic field. |
Often used with a full-scale converter. It can be used in direct-drive or geared turbines. |
|
Electrically excited synchronous generator |
Uses electrical current to create the rotor’s magnetic field. |
Can be designed for geared or direct-drive systems. Its excitation equipment depends on the design. |
These terms describe different parts of a turbine’s electrical system. DFIG describes a generator arrangement. A full converter describes how a generator connects electrically to the grid; it isn’t a generator type. Full-converter systems can use different generator designs.
Older turbine systems may also use wound-rotor induction generators with variable slip. These are useful to know about when reading historical information, but they should not be confused with modern DFIG systems.
An induction generator creates its magnetic field through the interaction between the rotor and stator. It needs reactive power, which may come from the grid or from suitable compensation equipment.
A DFIG is a type of wound-rotor induction generator. The converter, connected to its rotor, enables variable-speed operation over a range and controls the rotor-side electrical power.
A synchronous generator’s rotor field rotates in step with the electrical field in the stator. That field can come from permanent magnets or electrical excitation. A permanent magnet generator doesn’t need a separate electrical supply to create its rotor field; an electrically excited machine does.
The generator and the rest of the electrical system need to work together. The generator type alone doesn’t explain the whole turbine design.
A geared turbine uses a gearbox to increase rotational speed before it reaches the generator. This allows the generator to operate at a higher speed.
A direct-drive turbine connects the rotor to the generator without a gearbox. Its generator is designed to produce power at lower rotational speeds and is typically larger. Permanent magnet synchronous generators are one option for direct-drive designs, but generator type and drivetrain configuration are separate choices.
Neither arrangement is automatically best for every turbine. The design depends on the turbine, its output, location, operating conditions and maintenance requirements.
A power converter manages the electricity produced by the generator before it reaches the grid. This matters because a turbine’s output varies with its operating speed.
In a DFIG system, a partial-scale converter connects to the rotor. In a full-converter system, the generator’s output passes through a converter before reaching the grid. The generator, converter and controls are designed to work together.
Onshore and offshore turbines can use different generator and converter arrangements. The location alone doesn’t identify which type of turbine uses.
Offshore access can make inspection and repair more difficult. Reliability, weight, drivetrain design and maintenance planning are important considerations, but no single generator type is used for every offshore turbine.
Small wind turbines vary, too. Their generators depend on the turbine design, controls and intended connection. Check the manufacturer’s technical specification to identify the equipment in a particular model.
A turbine specification may list different parts of the system separately. Look for:
These details give a clearer picture than a general description, such as “synchronous generator”.
No. A wind turbine’s rotor drives its generator. A diesel generator uses an engine to drive an alternator. They’re different systems designed for different applications.
Bellwood supplies alternators for commercial, industrial and standby generator sets. Its alternator range is intended for those generator-set applications.
These alternators aren’t automatically suitable replacements for wind-turbine generators. Wind-turbine equipment must match the turbine’s speed range, drivetrain, controls and electrical connection. Check any proposed replacement against the turbine manufacturer’s specification and with a qualified engineer.
Bellwood supplies alternators for commercial, industrial and standby generator sets. Browse the alternator range or contact the Bellwood team with your generator’s make and model, existing alternator details and required output. For wind-turbine equipment, confirm compatibility with the turbine manufacturer or a qualified engineer.