30-05-2012, 11:42 AM
Induction Motor as a Induction Genrator
Induction Motor as a Induction Genrator.pptx (Size: 69.22 KB / Downloads: 43)
Generator Operation
• In generator operation
– the rotor spins above synchronous speed
– it develops a counter-torque that opposes the overspeed
• same effect as a brake
– the rotor returned the power as electrical energy instead of dissipating it as heat
• referred to as asynchronous generation
• kinetic energy is converted into electrical energy
– the motor delivers active power to the electrical system
– the electrical system must provide reactive power to create the stator’s rotating
magnetic field
• Active power delivered to the line is directly proportional to the slip
– higher engine speed produces greater electrical output
– rated output power is reached at very small slips, |s | < 3%
Reactive power sources
Capacitor across the motor may supply the vars
The motor supplies 3 phase electrical load without an external 3 phase supply.
Frequency generated is slightly less than corresponding to speed of rotation.
The terminal voltage increases with capacitance but limit by iron saturation.
Insufficient capacitance causes the voltage not to build up
Capacitors must supply at least the vars normally absorbed when machine operates as a motor