apukäämityksiä

Apukäämityksiä, often translated as auxiliary windings or starting windings, are secondary windings found in electric motors, particularly single-phase induction motors. Their primary purpose is to facilitate the starting of the motor. Single-phase motors inherently lack a rotating magnetic field, which is necessary for them to begin rotating. Apukäämityksiä are employed to create this necessary phase difference.

During startup, an auxiliary winding, typically wound at a different angle to the main winding, is energized. This creates a temporary magnetic field that is out of phase with the main winding's field, generating a rudimentary rotating field. This field provides the initial torque to get the rotor spinning. Once the motor reaches a certain speed, usually around 75% of its rated speed, the apukäämityksiä are disconnected from the circuit. This is often achieved using a centrifugal switch or an electronic relay, preventing them from overheating and consuming unnecessary energy.

The apukäämityksiä are usually constructed with fewer turns and a higher resistance wire compared to the main winding. This design characteristic helps in achieving the required phase shift and ensuring that the current in the auxiliary winding leads the current in the main winding, thereby producing the starting torque. The effectiveness of the apukäämityksiä directly impacts the starting torque and efficiency of the motor. Different types of single-phase motors, such as split-phase, capacitor-start, and capacitor-run motors, utilize apukäämityksiä in conjunction with capacitors to optimize starting performance and running characteristics.