Description
three phase induction motor rewinding. How to repair motor diy at home. Three phase induction industrial motor rewinding. Motor winding formula. Three phase asynchronous motor is most common used motor in the world. It has very good efficiency and low manufacture and maintain costs. Two main parts of motor are rotor and stator. Rotor is usually made as squirrel-cage, and it is inserted in stators hole. Stator is made out of iron core and winding.
Stator is used to generate magnetic field. 3 phases generates rotation magnetic field so we don't need capacitor on three phase motor. Rotation magnetic field "cut" squirrel-cage, where it induces voltage. Because cage is short-circuited, voltage generates flow of electric current. Current in magnetic field generates force.
Because magnetic field must rotate faster than rotor to induce voltage in rotor. That's why motor speed is a little bit less then magnetic field speed ((3000 rpm [Magnetic field] -- 2810 rpm [Electric motor])). That's why we call them Three phase ASYNCHRONOUS electric motor.
Motors Inscription board
On the motors inscription board we can find most useful information about motor:
Motors nominal voltage (for star (Y) and triangle (D) motor connection) [V]
Motors nominal current (for star (Y) and triangle (D) motor connection) [A]
Power of the electric motor [W]
Power factor cosFi
Rotation speed [rpm]
Nominal frequency [Hz]
Open the cover of conduit box.
Before measuring remove all connections in conduction box. Measure resistance for each winding, resistance between two different winding and resistance between winding and motors frame.
Resistances of three winding should be same (+/- 5%). Resistance between two winding and winding - frame should be more than 1,5 Mohm.
You can detect burned motors winding by unique smell (smells like burned lacquer).