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.