käivitusmähised

Käivitusmähised, also known as starting windings or start coils, are a crucial component in many AC electric motors, particularly single-phase induction motors. Their primary function is to create a rotating magnetic field, which is essential for initiating the motor's rotation. Without this initial push, the rotor would simply vibrate and not turn.

These windings are typically made of a lighter gauge wire and are designed to have a higher resistance and lower inductance compared to the main winding (running winding). This difference in electrical characteristics is key to their operation. When the motor is energized, current flows through both the starting and main windings. However, due to the phase difference created by the different impedances, the starting winding produces a magnetic field that is out of phase with the field produced by the main winding. This out-of-phase relationship generates the necessary rotating magnetic field to get the motor spinning.

Once the motor reaches a certain speed, typically around 70-80% of its rated speed, the starting winding is no longer needed and is usually disconnected from the power supply. This disconnection is typically achieved by a centrifugal switch, a potential relay, or a current relay, depending on the motor's design. The running winding then takes over to maintain the motor's operation. The use of starting windings allows for the design of simpler and more cost-effective single-phase motors for a wide range of applications.