Variable speed motor structure and working principle

Update:19 Apr 2019

The variable speed motor is composed of three parts: a […]

The variable speed motor is composed of three parts: a common squirrel cage asynchronous motor, an electromagnetic slip clutch and an electric control device. The variable speed motor is used as a prime mover, and when it rotates, the armature of the clutch is rotated together, and the electric control device is a device that provides the excitation current of the slip coil excitation coil. Here we mainly introduce the electromagnetic slip clutch, which includes three parts: armature, magnetic pole and excitation coil. The armature is a cylindrical structure made of cast steel, which is connected with the rotating shaft of the squirrel cage asynchronous motor, commonly known as the active part; the magnetic pole is formed into a claw-shaped structure and is mounted on the load shaft, commonly known as the driven part. The active part and the driven part have no mechanical connection. When the exciting coil passes a current, a magnetic field is generated, and the claw-shaped structure forms a plurality of pairs of magnetic poles. At this time, if the armature is dragged and rotated by the squirrel cage asynchronous motor, it cuts the magnetic field interaction and generates torque, so that the magnetic pole of the driven portion rotates together with the active portion armature, and the former rotates lower than the latter. Because the armature can cut the magnetic lines of force only when there is relative movement between the armature and the magnetic field. The magnetic pole rotates with the armature. The principle is not fundamentally different from the principle of the rotating magnetic field of a conventional asynchronous motor rotor following the stator winding. The difference is that the rotating magnetic field of the variable speed motor is generated by the three-phase alternating current in the stator winding, and the magnetic field of the electromagnetic slip clutch is composed of the exciting coil. The DC current is generated and acts as a rotating magnetic field due to the rotation of the armature.