What will happen when I change the excitation in synchronous motor or generator?
Synchronous Motor or Generator can run in both form.
- Over excitation or
- Under excitation.
When run as alternator alone:
Over and Under excitation will increase or decrease the terminal voltage.
When run as alternator connected with the grid or infinite BUS
- Over excitation will deliver additional inductive VAR to the grid and and will operate at lagging power factor
- Under excitation will absorb reactive power from the grid and will operate at leading power factor.
When run as Synchronous Motor and connected with the system:
- Over excitation will deliver additional leading VAR to the system and and will operate at leading power factor
- Under excitation will operate at lagging power factor and will increase inductive VAR of the system.