Effect of sudden loss of reactive power for an induction generator

  • Thread starter anon6912
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  • #1
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So im having this problem at work where a 150kW induction motor is being used as an induction generator. There is a capacitor bank in parallel to the induction generator which is primarily for PFC(the reactive power requirement of the generator is fed by the grid).

Assume the induction generator is islanded( i.e the capacitor bank is out, the grid is out and the induction generator is the only thing that's connected to the load)

What would happen to the induction generators speed?
If a step by step explanation on what will happen would be great.

From my thinking when the capacitor bank and the grid power goes out the generator has no source of vars to sustain the stator magnetic fields.
(i.e stator magnetic field will collapse pretty much instantly which will produce a large voltage in the stator coils due to Ldi/dt)

1)After this initial Ldi/dt voltage spike it would cause a large current to flow in the stator coils?and it would oscillate?

2)Or because of the lack of reactive power the stator will have no magnetic field and that would stop inducing and emf on the rotor which will collapse the rotor magnetic field and stop the generator all together?


say the magentic field is not there anymore in the stator, would it cause the rotor(which is connected to an impeller) to freewheel and destruct itself?



I know this is a bit of a long question:)
 

Answers and Replies

  • #2
anorlunda
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Yes it will collapse unless there are phase correcting capacitors build in.
https://en.wikipedia.org/wiki/Induction_generator said:
An induction generator usually draws its excitation power from an electrical grid. Because of this, induction generators cannot usually "black start" a de-energized distribution system. Sometimes, however, they are self-excited by using phase-correcting capacitors.
 

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