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INDUCTION GENERATOR AND SYNCHRONOUS INDUCTION MOTOR
PRESENTED BY:NAMANI SRILAHARIPAVITHRAN SELVAM
INDUCTION MOTORDEFINITIONAn induction generator or asynchronous
generator is a type of alternating current (AC) electrical generator that uses the principle of induction motor to produce power.
Torque speed characteristics
Slip 0≤s≤1 – runs as a motor(Normal operation
Slip (s)>1–machine works in braking mode(Plugging).
To run as induction generator, Slip <0 i.e. NEGATIVE
When the slip of the induction motor is negative i.e when the induction motor runs faster than synchronous speed, the induction motor runs as a generator called induction generator.
Stator of I.G – connected to voltage source – produce RMF at synchronous speed
When rotor is rotated above Ns, stator disconnected- no generating action
Note: Direction of rotation of motor and generator are opposite for same current direction
Rotor driven at synchronous speed
Rotor conductors cut flux of rotating field in opposite direction than that of motor
Rotor currents are reversed
Due to transformer action, currents are induced in stator
Induction motor is run as generator
IG is not self-excited
It must be connected to a.c supply
It is operated parallel with synchronous machines
For eg: To supply load which requires lagging current(IG supplies only leading current)
So, Lagging current can be achieved with the help of synchronous generator parallel with induction generator
If bank of delta connected capacitors is operated in parallel with induction generator then, reactive power is met by capacitors.
The induction generator is said to be isolated induction generator.
Frequency of I.G = Frequency of the line
Comparison Induction generator and Synchronous generator It will not require d.c excitation
It is not self excited but external a.c supply of fixed frequency is required.
The frequency of induction generator is decided by the frequency of excitation voltage which is supplying current to it.
Synchronization of generator is not required as no emf is generated until it is connected.
Advantages Synchronization for induction generator is not required.
The construction is rugged for rotating parts.
Unlike in synchronous machines, there is no danger of hunting or drop out of synchronism for induction generators.
When it is short circuited, it delivers small power as its excitation quickly reduces to zero.
More suitable for high speeds
With the help of excitation supply and frequency, the voltage and frequency of induction generator are controlled
Disadvantages It must be run in parallel with synchronous
machine.
The load is not deciding the power factor but
power factor depends on slip.
APPLICATIONUsed in railway for braking purposesEnergy generated by induction generator
is given to the line so that the load on main generating station is somewhat relieved.
SYNCHRONOUS MOTORDEFINITION• A synchronous motor in one in which the rotor
rotates at the same speed as the rotating magnetic field in the stator.
INDUCTION MOTORDEFINITION• An induction generator or asynchronous
generator is a type of alternating current (AC) electrical generator that uses the principle of induction motor to produce power.
ADVANTAGESCan start & synchronize against more than full
load torque.
Smaller capacity of exciter is required.
No separate damper winding is required.
No separate starting & control equipments are required
DISADVANTAGES It will not give large overload capacity.
Variation of power factor is large.
Speed variation is not possible.
APPLICATION• Applications where in load torque is remaining
nearly constant, this motor can be used.