Explain the principle of operation of a synchronous generator with the aid of calculations.
A synchronous generator converts mechanical energy to Electrical energy. The source of which creates the mechanical energy may be a steam engine, water falling through a waterwheel, a wind turbine, a hand crank or via compressed air.
A synchronous generator has 2 main parts:
1) Stator
2) Rotor
The Rotor is the rotating part whereas the Stator is the stationary part, hence where they get their names from.
- Rotor has north and south poles protruded on it, in the case of salient poles, on which Laminations are used to reduce Eddy losses. The north and south poles of the rotor are wrapped with windings, the number of poles will always be even and dependent on the speed of the generator.
- A separate DC supply is provided to the rotor with the help of slip rings and brushes and the current is passed to windings on the rotor. The rotor is attached to the shaft which makes the rotor rotate. As winding carrying current is under permanent magnet poles of rotor it will itself creates its own magnetic field
- Stator is the stationary part . it is the section made of steel plates combined together with windings on it at 120 degree intervals to balance it out.
- Now as the rotor rotates its magnetic field will cut the windings of the Stator and this in turn will cause an AC voltage to be induced in the Stator windings and an AC current is drawn.
A synchronous generator operates on the amount of poles wound within its stator. The more poles in the stator equates to a smaller rev/min. For example a 2 pole generator would run at maximum of 3000r/min whereas a 4 pole generator would only run at 1500r/min. This is done with the equation F=NsP to find the speed at which the motor runs at. The rotation of the shaft is synchronized with the frequency of the supply current, which means the rotation period is exactly equal to the number of AC cycles.
I would also use Faradays law to help explain the principle of operation with calculations. Faradays law means that the amount of voltage created is equal to the change in magnetic flux divided by the change in time. The bigger the change you have in the magnetic field, the greater amount of voltage.
Fleming's right hand rule (for
generators) shows the direction of
induced current when a
conductor moves in a
magnetic field. No current is induced if the motion of the conductor is in line with the field, going either direction, and the same can be said if it runs parallel to current.
The right hand is held with the
thumb,
first finger and
second finger mutually perpendicular to each other (at right angles), as shown in the diagram .
- The Thumb represents the direction of Motion of the conductor.
- The First finger represents the direction of the Field. (north to south)
The Second finger represents the direction of the induced or generated Current (the direction of the induced current will be the direction of conventional current, from positive to negative.
This is the answer ive came up with so far, any criticisms or improvements I can make to it?
