An electric motor transforms electrical energy into mechanical energy to drive mechanical equipment. Among AC motor categories, synchronous motors and asynchronous motors share certain common features, yet show obvious distinctions in operating logic and overall performance.

Working Principle of AC Motors

DC motors generate mechanical force when magnetic fields interact with current‑carrying conductors. By contrast, AC motors operate based on the rotating magnetic field (RMF). The stator holds multiple windings. Once fed with AC input power, these windings create a rotating magnetic field revolving around the rotor assembly.

Slip describes the speed gap between the stator rotating magnetic field and the actual rotor speed. Zero slip means the rotor rotates exactly at the same velocity as the stator magnetic field, which defines an AC synchronous motor. An asynchronous motor comes with non‑zero slip, where a measurable speed difference exists between the stator field and rotor.

Synchronous Motor

As suggested by its name, the rotor inside a synchronous motor runs at synchronous speed, matching the rotational speed of the stator‑generated magnetic field.

AC power fed to the stator produces the rotating magnetic field. The rotor builds up its magnetic field in two mainstream solutions: external DC excitation delivered via slip rings, or built‑in permanent magnets.

Rotor magnetic poles are configured to match or form integer multiples of stator pole counts. After power‑on, the rotor magnetic field locks onto the stator rotating field and spins at identical speed.

Synchronous speed is determined by supply frequency and stator winding pole quantity. Its rotational speed stays stable regardless of load fluctuation. Speed adjustment for synchronous motors can only be achieved by modifying input power frequency. Typical synchronous motors cover 8‑40 pole specifications.

Asynchronous Motor

For asynchronous motors, rotor speed cannot keep pace with the stator rotating magnetic field. Practically, the rotor always runs slower than the stator RMF, and this phenomenon originates from slip.

Two mainstream rotor constructions are available: squirrel‑cage rotor and wound rotor. Squirrel‑cage rotors adopt thick copper bars short‑circuited by end conductive rings. Wound rotors install multi‑turn windings on laminated steel iron cores.

The stator rotating magnetic field induces current inside the rotor. Induced rotor current further generates an independent rotor magnetic field. Owing to electromagnetic induction working theory, asynchronous motors are also widely named induction motors. They cannot reach true synchronous speed; actual operating speed falls below synchronous speed and is subject to slip rate. YB2 series explosion‑proof asynchronous AC motor belongs to this product category.

Summary

Synchronous motors deliver higher efficiency yet come with higher procurement costs. They suit ultra‑low‑speed working scenarios and can realize power‑factor correction. Asynchronous (induction) motors feature low cost and simple operation, fit for high‑speed and variable‑speed working conditions. Feel free to reach out for further motor solutions. Our product portfolio includes permanent magnet synchronous motors, low‑voltage squirrel‑cage motors and other related models.