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synchronous to squirrel cage induction conversion

synchronous to squirrel cage induction conversion

synchronous to squirrel cage induction conversion

(OP)
I saw the post about using a VFD on a WRIMotor with the rotor shorted.  I wondered if one could short the armature windings (or connect a resister in the circuit)of an AC alternator and use it as an induction generator.  Might be easier to switch back and forth with a brush/slip ring design armature vs a brushless design.

The engine speed would have to increase, but that would be a simple matter on most generator sets.

Maybe this would solve the problem of not having backup power available from an induction generator.

Jim

RE: synchronous to squirrel cage induction conversion

I don't think that using the rotor from a synchronous alternator would make an efficient induction generator, even with the brushes shorted as you suggest.  It would be like an induction motor with only a very small number of rotor slots albeit effectively very large ones.

RE: synchronous to squirrel cage induction conversion

Synchronous to squirrel cage induction conversion is not recommended. Adding to the disadvantages referred by UK-Pete, since the air gap is extremely high the magnetizing current to cross it and induce in the rotor bars is to high and with high leakage of flux lines ( When it works as synchronous, the field is created in the rotor).
The magnetizing current needs to be provided by the load line. If you do not have a reference three phase system it will not produce electricity at all.

RE: synchronous to squirrel cage induction conversion

(OP)
Thanks aolade and ukpete.
Besides inefficiency, do you think it would hurt the synchronous alternator to do this.  Maybe if the armature current didn't exceed "normal" levels.

I understand the implications of induction generators vs excitation, that is what I am trying to get around by having the wound rotor and AVR for backup use.

Jim

RE: synchronous to squirrel cage induction conversion

Working as induction machine, the weak link are the rotor cage bars, rather than the stator winding. Unless a reduced power is handled (well below the nominal current as synchronous machine), the overheating will destroy the amortisseur winding (rotor cage)in a short operating time.

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