Generators and motors
Posted in Physics, Electromagnetic machinesGenerators
Generators convert mechanical energy into electrical energy. Typically a generator is made up of a static component called a stator which provides a magnetic field and a conductor called a rotor. When the rotor is turned it cuts the flux lines of the static magnetic field. The change in flux experienced by the rotor induces an EMF. This idea comes from electromagnetic induction
Motors
Motors are built the same as generators with the use of a stator and rotor. In a motor however a current is put across the rotor which causes a force to act on the rotor causing it to rotate.
Force on a conductor
The force on the rotor in a motor or any current-carrying conductor in a magnetic field can be calculated using the equation:
Where is the current in the conductor,
is the length of the conductor and
is the magnetic field strength the conductor is in.
This is the force which causes the rotor in a motor to turn generating mechanical power.
Motors as generators as the same thing
A motor can act like a generator and a generator can act like a motor.
Motors and generators (Back EMF)
Motors also act as generators. When the rotor is turning it is cutting the magnetic field just as a generator does, this causes an emf to be induced in the rotor which 'pushes back' on the EMF supplied to the rotor. This induced EMF is known as 'back EMF'.
Generators as motors
When a generator is generating electricity a current is being induced in the rotor. This acts just like a motor and a force acts on the rotor to turn it. Unfortunately the force acts in the opposite way to the mechanical power turning the rotor and so it requires more power to turn the rotor.