Single-phase asynchronous motor has several sets of stator windings and common winding faults

How many sets of stator windings does a single-phase asynchronous motor have?

Single-phase asynchronous motors have only one set of stator windings. In single-phase asynchronous motors, since there is only one phase of current, only one stator winding is needed to generate the magnetic field. The number of coils, turns and arrangement of this winding will affect the performance and characteristics of the motor, such as starting torque, operating efficiency and noise.

The stator of a single-phase asynchronous motor consists of three parts: the frame, the core, and the winding. They are described as follows.

The motor base is made of cast iron, cast aluminum and steel plate, and its structural form depends on the application and cooling method of the motor. Single-phase motor bases are generally divided into open, protective and closed types. The stator core and winding of the open structure are exposed and naturally cooled by the surrounding air. They are mostly used in some applications where the whole machine is integrated, such as washing machines. The protective structure is to open some necessary ventilation channels on the ventilation path of the motor, while the core and winding of the motor are covered by the motor base. The closed structure is that the entire motor is sealed, the inside of the motor is isolated from the outside, to prevent external erosion and pollution, and the heat inside the motor is dissipated by the motor base. When the heat dissipation capacity is insufficient, a fan is added to cool the outside.

In addition, some special electric motors do not require a base, and the motor can be directly assembled into one with the whole machine, such as electric drills, electric hammers and other portable power tools.

The stator core is mostly made of silicon steel sheets with small iron loss, good magnetic conductivity and thickness of 0.35-0.5mm, which are punched and laminated. The stator and rotor sheets are evenly slotted. Since the air gap between the stator and rotor of the single-phase asynchronous motor is relatively small, generally 0.2-0.4mm. In order to reduce the influence of electromagnetic noise and tooth harmonic additional torque caused by the slotting of the stator and rotor. The stator slot is mostly semi-closed. The rotor slot is closed or semi-closed, and the rotor skew slot is also used to reduce the influence of stator tooth harmonics. The stator core of the concentrated winding shaded pole single-phase motor adopts a salient pole shape, which is also punched and laminated with silicon steel sheets.

The stator winding of a single-phase asynchronous motor generally takes the form of a two-phase winding, namely the main winding and the auxiliary winding. The axes of the main and auxiliary windings differ by 90° electrical angle in space. The number of slots, slot shapes, and turns of the two-phase windings can be the same or different. Generally, the main winding occupies 2/3 of the total number of stator slots, and the auxiliary winding occupies 1/3 of the total number of stator slots. However, it should be determined according to the requirements of various motors.

Common stator winding forms used in single-phase asynchronous motors include single-layer concentric winding, single-layer chain winding, double-layer stacked winding and sinusoidal winding. The stator of shaded-pole motors is mostly concentrated winding, with a short-circuit copper ring shaded-pole coil embedded on a part of the magnetic pole surface.

The stator winding wires are made of high-strength polyester enameled wire. After the coils are wound on the wire mold, they are embedded in the stator slots with slot insulation. After insulation treatment such as varnishing and drying, the mechanical strength and thermal conductivity of the windings can be improved.

Common faults of single-phase asynchronous motor windings

The common faults of single-phase asynchronous motor windings are mainly the following:

Short circuit fault: When a short circuit fault occurs in the stator coil, it will cause difficulties in starting the motor, decreased acceleration, and increased motor temperature.

Open circuit fault: When an open circuit fault occurs in the stator coil, the motor will fail to start or operate normally, and there is also the risk of the coil burning out.

Loose winding: Loose winding can cause problems such as motor vibration and increased noise. In severe cases, it may cause the coil to fall off or the motor to fail.

Insulation aging: Due to the working environment, high voltage or long use time, the insulation material of the winding may age, resulting in a decrease in insulation strength, which is prone to leakage and may lead to motor failure.

Overheating failure: Due to excessive load or high ambient temperature, the temperature of the motor may rise too quickly, causing the winding to overheat and cause motor failure.

To avoid the above faults, it is recommended to regularly inspect and maintain the single-phase asynchronous motor and strengthen daily maintenance to avoid motor overload or long-term operation at excessively high temperatures.

How to wind the stator coil of a single-phase asynchronous motor

There are two ways to wind the stator coil of a single-phase asynchronous motor, namely single-layer winding and double-layer winding.

Single-layer winding: The stator coil of the single-layer winding method consists of several turns, which are wound in the tooth slots of the stator core. When winding, each turn of the coil is wound in one direction, and the winding direction is the same, so that the magnetic field direction of the coil can be consistent. The single-layer winding method is suitable for low-power single-phase asynchronous motors.

Double-layer winding method: The stator coil of the double-layer winding method is wound by two layers of coils, and the number of turns of each layer of coils is the same. Among them, the winding direction of the upper coil and the lower coil is opposite, which can effectively reduce the leakage inductance of the motor and improve the efficiency and power factor. The double-layer winding method is suitable for medium and high power single-phase asynchronous motors.

It should be noted that the stator coil winding of the single-phase asynchronous motor needs to be carried out according to certain rules to ensure the normal operation of the motor. At the same time, different winding methods will also affect the performance and characteristics of the motor, so it is necessary to choose according to the actual situation.