A Squirrel Cage Induction Generator (SCIG) is a type of electric generator that operates based on the principles of electromagnetic induction. It is commonly used for converting mechanical energy into electrical energy in various applications, such as wind turbines, hydroelectric power plants, and some types of industrial machinery.
Here's how it works:
Rotor Design: The rotor of a SCIG consists of a cylindrical assembly of conductive bars or "squirrel cage" bars. These bars are typically made of copper or aluminum and are short-circuited at both ends by end rings. The shape of this rotor gives the generator its name, as it resembles a squirrel cage wheel.
Electromagnetic Induction: When the rotor of the SCIG is rotated (usually by an external mechanical source such as wind or water flow), it cuts through the lines of the magnetic field produced by the stator windings. This action induces a voltage in the rotor conductors according to Faraday's law of electromagnetic induction.
Induced Current: The induced voltage in the rotor conductors causes electric currents to flow through the bars of the squirrel cage. These currents, in turn, create their own magnetic fields that interact with the stator's magnetic field.
Electricity Generation: The interaction between the rotating magnetic field produced by the rotor currents and the stationary magnetic field produced by the stator windings induces an electric current in the stator windings. This electric current in the stator windings is what generates the electrical output of the generator. The output frequency and voltage are determined by the rotational speed of the rotor and the number of poles in the stator winding.
SCIGs are known for their simplicity, ruggedness, and ability to handle varying mechanical input conditions. However, they have certain limitations, such as a lack of self-excitation capability, which means they need an external source of magnetization (excitation) to start generating electricity. They are commonly used in applications where the mechanical input (such as wind or water flow) can vary, as their speed can adapt to changes in the input without requiring complex control systems.
In contrast to SCIGs, there are other types of generators like Doubly Fed Induction Generators (DFIGs) used in wind turbines, which have additional electronics to control the rotor current and allow for variable speed operation and improved efficiency.