How Electric Motors Work - 3 phase AC induction motors ac motor

• Electrical motor


  One of the most important devices ever to be invented, used everywhere from pumping water to powering elevators, cranes, and cooling nuclear power stations
• How an electrical motor works

  1. Look inside the motor

  2. Electrical energy converted to mechanical energy

  3. Shaft rotates to drive pumps, fans, compressors, gears, pulleys

  4. Fan cools the motor

  5. Stator generates rotating electromagnetic field

  6. Rotor (squirrel cage) rotates due to interaction with stator field
• Stator


  • Stationary, contains coils that generate rotating electromagnetic field
• Rotor


  • Squirrel cage type, rotates due to interaction with stator's rotating magnetic field
• Laminated steel sheets in rotor improve efficiency by reducing eddy currents
• Inductor


  Coils of wire that produce a magnetic field when current flows through them
• How a rotating magnetic field is generated

  1. 3 sets of stator coils connected to 3-phase power supply

  2. Coils produce magnetic fields that change in intensity and polarity at different times

  3. Combining the 3 fields creates a rotating magnetic field
• Rotor bars


  Shorted at each end, induce currents that create magnetic fields that interact with stator field, causing rotor to rotate
• Electrical terminal box


  Contains 6 terminals (U1, V1, W1, U2, V2, W2) for connecting 3-phase power supply
• Connecting the motor to 3-phase power

  1. Delta configuration: U1 to W2, V1 to U2, W1 to V2

  2. Star/Y configuration: W2 to U2 to V2
• Delta configuration


  Electricity flows between phases as AC reverses direction at different times
• Star/Y configuration


  Phases share a common neutral point, uses less voltage and current than delta
• Delta configuration has higher voltage (400V line-to-line) and current (34.6A) than star configuration (230V, 11.5A)