Motor winding type and its characteristics

Therefore, increasing the life of the winding is of special importance. Winding manufacturing processes include coil manufacturing, winding embedding, and insulation processing. Many manual operations, labor intensity, quality is difficult to stabilize. Therefore, it is an important task for motor manufacturers to correctly master the manufacturing process of motor windings and improve the quality and service life of windings.


Armature winding

The armature winding is installed in the armature core (or stator core) slot, and can be divided into two categories: soft winding and hard winding, depending on its structure and manufacturing method.

●Soft winding

The soft winding is wound by an insulated round wire. Commonly used in small motors with semi-closed slots, operating voltages not exceeding 500 volts. The windings can be made as a single layer or a double layer, with one coil edge scattered in each slot of the single layer; two coil sides are scattered in each slot of the double layer. From the technical analysis, a small AC motor of 10 kW and below should adopt a single-layer winding, because there is no interlayer insulation in the groove, and the embedding is convenient; the groove space utilization is good, but the winding ends overlap each other and are not easy to be shaped. For motors above 10 kW, the inner diameter of the core is large, and the double-layer winding is more used because it can select a suitable short pitch to weaken the harmonic magnetic potential and the winding ends are arranged neatly.


In addition, there are single-dual hybrid windings and Y-△ hybrid windings in AC motors. In a single-deck hybrid winding, one of the slots is a single layer and the other is a double layer. It has a short-distance effect. Compared with a double-layer winding with the same short distance, its winding end wiring is shorter, which is advantageous for 2P motors.

In the Y-△ hybrid winding, the coil of each phase of each pole is divided into two types: △ shape and Y shape. The number of turns and the wire diameter of the two coils are different. When the wire is embedded, the two coil groups are alternately scattered. First, the delta system and the Y-shaped system are respectively coupled and then mixed into a final connection. Such a winding can eliminate higher harmonic components in the magnetic potential and increase the fundamental distribution coefficient. However, the two kinds of windings are inconvenient in the wiring of the wires, and the error is easy to occur, and the process management is very important.

According to the different embedding methods, the soft winding can be divided into embedded soft winding, wrap-around soft winding and penetrating soft winding.

(1) When the embedded soft winding is manually operated, the multi-turn loosely-embedded coil is dispersed into the core groove through the slot. It is mostly used for small AC motor stators or wound rotors, as well as small DC armatures. Mechanized embedding processes have been promoted for mass-produced small stators.

(2) The wound soft coil is directly wound into the core slot by the insulated round wire, and is mostly used on a DC armature or an AC rotor with a small number of poles. It is usually hand-wound, and for mass-produced DC armatures or rotor windings, it is processed by a special wire-bonding machine.

(3) The penetrating soft winding core is a closed slot or a semi-closed slot, the slot width is smaller than the embedded wire diameter, and the wire is an insulated round wire or a plurality of stranded wires, which are penetrated by the two ends of the groove. The threading work is very large and is only used for special motors, such as medium frequency motors and water-filled submersible motors.


● Hard winding

The hard winding consists of a molded coil made of insulated flat wire or bar. According to different bulk methods, it can be divided into embedded and plug-in.

(1) The embedded winding core is an open slot or a semi-open slot, and the winding component is a multi-turn or single-turn forming coil. When the multi-turn forming coil is used for the open slot, it is generally covered and insulated from the ground and insulated. When used in a semi-opening slot, the coil is formed by winding two insulated flat conductors, which are separated into slots and are flattened in the slots.

The single-sided forming coil is divided into a full circle type and a half circle type. The full-circle type is mostly used for medium-sized DC armatures; the half-turn type is mostly used for large-scale steam turbine generators and hydro-generators.

Generally, a single-sided forming coil has a large conductor cross section, which is composed of a plurality of insulated flat conductors and is bent on a special mold or molding apparatus. For large generators above 300 kW, due to the large conductor size, the leakage magnetic field in the tank will cause uneven distribution of the conductor current, which will increase the winding loss. In order to overcome this shortcoming, the coil is often woven by multi-strand insulated flat conductors.

(2) The plug-in hard coil core is a closed slot or a semi-closed slot, and the winding component is a half-turn bar. When used in an asynchronous motor wound rotor, the coil conductor is bent by a beryllium copper strip. Bend one end first, and the other end is inserted into the groove and then molded. For large motor stators, some use involute half-turn transposition braided coils, which are inserted into the slots and welded with the headgear. Asynchronous motor welding squirrel cage windings, synchronous motor damper windings or starting windings, as well as large DC motor compensation windings also use plug-in windings.

The pole winding is mounted on the pole core. According to the materials used and the winding method, it can be divided into two types: insulated wire winding (round wire or flat wire) and ribbon wire winding. The strip conductor can be divided into two types: flat winding (wide side bending) and flat winding (narrow side winding).

Winding manufacturing processes vary by structure. The key to the manufacture of soft windings lies in the bulk winding, taking the example of embedded soft windings. The main manufacturing process is: winding → coil → wiring → inspection → insulation treatment. The key to hard winding manufacturing is coil manufacturing. The coil manufacturing method varies according to different insulation structures and processing techniques. Taking the open slot embedded hard winding as an example, the main manufacturing process is winding or wavy coil → rising shape → shaping → inter-turn insulation → gelation treatment → package-to-ground insulation → hot press forming → inspection → winding embedding → test.