An induction motor starts through a process called motor starting, which involves providing an initial push or torque to the rotor (the rotating part of the motor) so that it begins to turn. Induction motors are commonly used in various applications, including industrial machinery, pumps, fans, and many household appliances. Here's a basic overview of how an induction motor starts:
Stator Voltage Applied: The first step in starting an induction motor is to apply a voltage to the stator windings. The stator is the stationary part of the motor and contains the primary winding, which is connected to the power supply. When the voltage is applied, an alternating current (AC) flows through the stator windings, generating a rotating magnetic field.
Rotating Magnetic Field: The rotating magnetic field produced by the stator induces currents, known as eddy currents, in the rotor. These currents create their own magnetic field, which interacts with the stator's magnetic field. As a result, a torque is produced on the rotor.
Rotor Movement: Initially, the rotor is stationary and at rest. The torque generated by the interaction of the rotating magnetic field with the rotor's induced currents causes the rotor to start moving. This movement is gradual, and the rotor accelerates as the torque increases.
Slip: In an induction motor, there is always a slight difference between the speed of the rotating magnetic field (synchronous speed) and the actual speed of the rotor. This difference in speed is called "slip." As the rotor accelerates, the slip decreases, and the motor approaches its synchronous speed.
Full Speed Operation: Once the rotor reaches a speed close to the synchronous speed, the slip becomes very small, and the motor operates at its intended speed. At this point, the motor has successfully started, and it continues to run as long as the stator voltage is maintained.
It's important to note that induction motors can experience high inrush currents during startup, which can put stress on the electrical system. To mitigate this, various methods are used, such as soft starters, variable frequency drives (VFDs), and star-delta starters. These methods help to control the starting current and reduce the mechanical and electrical stress on the motor and connected equipment.
Keep in mind that the exact startup process and controls may vary depending on the specific application and the type of induction motor being used.