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Hi Guys,
In case of an Induction Generator (IG) connected to grid, the rotor runs at super synchronous (above synchronous) speed exhibiting -ve slip. This is possible since the grid frequency is fixed at say, 50Hz. However, in case of a Self Excited Induction Generator (SEIG), it starts off as a synchronous generator at low speeds due to residual magnetism. As the rotor speed eventually increases, the external capacitor injects sufficient reactive power into the stator to maintain air-gap excitation flux.
But the stator current frequency of SEIG is determined by rotor speed and hence the excitation air-gap flux would rotate at the same speed as that of the spinning rotor (if a 3 phase SEIG is considered). In this case, how will the SEIG develop output power if slip between rotor and air-gap flux is zero?.. as at every step the increment in rotor speed will cause a proportional increment in stator frequency and at each step, the air-gap excitation flux will be in synchronism with the rotor speed resulting in zero slip. Zero slip would mean zero generated output power!
Can someone pls. clear the above concept for me? Also can this concept be applied to a single phase SEIG? Pls. help
Kind regards,
Shahvir
In case of an Induction Generator (IG) connected to grid, the rotor runs at super synchronous (above synchronous) speed exhibiting -ve slip. This is possible since the grid frequency is fixed at say, 50Hz. However, in case of a Self Excited Induction Generator (SEIG), it starts off as a synchronous generator at low speeds due to residual magnetism. As the rotor speed eventually increases, the external capacitor injects sufficient reactive power into the stator to maintain air-gap excitation flux.
But the stator current frequency of SEIG is determined by rotor speed and hence the excitation air-gap flux would rotate at the same speed as that of the spinning rotor (if a 3 phase SEIG is considered). In this case, how will the SEIG develop output power if slip between rotor and air-gap flux is zero?.. as at every step the increment in rotor speed will cause a proportional increment in stator frequency and at each step, the air-gap excitation flux will be in synchronism with the rotor speed resulting in zero slip. Zero slip would mean zero generated output power!
Can someone pls. clear the above concept for me? Also can this concept be applied to a single phase SEIG? Pls. help
Kind regards,
Shahvir
