Motor winding repair 1. Short circuit of stator winding

Winding short circuit refers to the direct collision of two copper wires caused by insulation damage to the coil wire, resulting in the current flowing directly into the circuit without passing through the load. The main reasons are high power supply voltage, excessive current, winding moisture and vibration wear, and repair of embedded wires

Accidentally scratching the insulation on the outer layer of the wire. After a short circuit fault occurs in an electric motor, high temperatures will be generated at the fault location, causing more insulation to burn out. Therefore, when checking for a short circuit fault in a running electric motor, it is recommended to stop the motor after it has stopped

Carefully observe whether there are any burnt marks or burnt smell on the motor coil. It is also possible to run the motor without load for a period of time, immediately remove the end cover after stopping, and touch the coil with your hand to see if the heating is uniform. Areas with inter turn short circuits generally have higher temperatures. But Zui has

The effective method is still to use the induction method, which utilizes the principle of electromagnetic induction to span a specially designed short-circuit transformer - short-circuit detector across the stator slot. After the short circuit detector is powered on, if the thin iron sheet or saw blade placed on the slot it crosses vibrates

Movement indicates that there is a short circuit phenomenon in the winding. If the winding is connected in multiple or triangular ways, the joints of each winding or phase winding need to be disassembled before inspection, otherwise it is difficult to detect. After finding the location of the short circuit, if it is found that the coil short circuit is not serious, wrap it around

When the group is not burned out, local repairs are often carried out by re wrapping the short circuit with insulation. If only one coil of the entire winding burns out the insulation due to a short circuit but is urgently needed, temporary measures can be taken by removing this coil or

Adopt a jumper method to remove the short circuited coil from the winding circuit, but at this time, all the wires at one end of the short circuited coil should be cut off (otherwise a short-circuit current will be generated), and then twist the wire ends on both sides together and wrap them with insulation material

Okay, if most of the winding insulation is burned out, a new winding needs to be replaced.

2. Inspection and repair of stator winding grounding

Winding grounding refers to the connection between the winding and the casing or iron core. The reasons include the coil being damp, the insulation material of the winding losing its insulation function, the coil overheating caused by long-term overload operation of the motor, which makes the insulation material brittle and damaged, and the operation during wire embedding

Accidentally causing the wire to collide with the iron core or end cap. If one phase of the winding is grounded, it will make the motor casing live, and if two phases are grounded, it will cause a short circuit and burn out the winding.

The commonly used light bulb method is to check whether the winding is grounded. Before inspection, the joints of each phase winding need to be disconnected so that the windings are not connected to each other. Then, connect the light bulb in series with the low-voltage power supply (12-36v), with one end connected to the motor housing and the other end alternately connected

On the joints of each phase winding, if the light bulb lights up, it indicates that there is a winding grounding phenomenon in this phase. If it is not directly grounded (touching the shell) and there is leakage between the winding and the iron core due to insulation moisture, there is a high leakage resistance between the winding and the iron core

The light bulb method may not be able to test it. In this case, several dry batteries and a speaker (earphone) can be connected in series. When there is a fault, a "click" sound can be heard, which is not present in good windings. If there is only one phase winding and the grounding point is in the end slot but there is no

When suffering from severe burns, there is no need to remove the coil. Simply place insulation paper on the grounding point and apply insulation paint. If the grounding point is in the slot, the wire needs to be gently pulled out of the slot, repaired, and then placed in the slot or replaced with a new coil. at this time

Attention should be paid to using insulating paper to pad the insulation groove (especially at the groove), to prevent the wire from directly touching the two ports of the groove and causing grounding again. If there are two windings that are grounded or have multiple grounding points, and the coil is severely damaged, it can be replaced according to the specific situation

A winding. In addition, sometimes the insulation of the wire may be cut and grounded due to one or several protruding silicon steel sheets in the stator core of the slot. In this situation, simply remove or flatten the protruding silicon steel sheet, and then re insulate the cut wire

Just enough.

3. Inspection and repair of stator winding open circuit
Winding open circuit refers to the disconnection of one or several coils due to wire breakage or loose end connections. The main reasons are motor overload, high voltage, excessive current, poor welding or detachment due to mechanical vibration. If there is one in the winding

Phase open circuit, the motor becomes single-phase and cannot start; If the stator is a winding with multiple connections, and one of the phases is open circuited, it will cause an imbalance in the three-phase current of the motor, causing the winding to heat up and the speed to decrease, and unable to reach the rated speed and rated power

It can also cause vibration and abnormal noise in the electric motor. The commonly used light bulb method is to check the open circuit of the winding. Connect the light bulb in series in one phase winding and connect the low-voltage power supply (12-36V). If the light bulb does not light up, it indicates that there is an open circuit in the winding.

If the disconnection is caused by poor contact due to joint detachment or the disconnection point at the end, it can be re welded firmly, then polished clean and wrapped with insulation. If the breaking point occurs in the slot, the broken coil should be removed and rewound.

4. Inspection and repair of rotor winding
For wound rotor asynchronous motors, common faults in the rotor winding include short circuits and loose joints. A short circuit in the winding can cause the rotor winding to heat up, even burn out, and result in an unbalanced current in the stator, while also producing abnormal noise. wind

If the joint is loose, it will reduce the motor speed (usually 1/2 of the rated speed when unloaded), decrease the torque, and cause fluctuations in the stator winding current (when measuring the stator current with a clamp ammeter, the needle will oscillate back and forth). inspect

Firstly, open the connection between the stator winding and the slip ring to make the rotor winding in an open circuit state. Then the three-phase current is passed into the stator winding. If the rotor rotates at a high speed (without reaching the rated speed), then it is said that

There is a short circuit in the rotor winding. In addition, a short circuit detector can also be used to check whether there is a short circuit in the rotor winding, using the same method as checking the stator winding. Loose connections in windings generally occur between the lead wires and slip rings of the windings

The connection is often caused by loose screws or poor welding. This type of malfunction can be detected by careful observation.

Classification of windings - Centralized windings

Centralized winding is applied to convex stator, usually wound into rectangular coils, wrapped and shaped with warp tapes, and then immersed in paint and dried before being embedded on the iron core of convex magnet. General commutator motor (including DC motor and AC motor)
The excitation coil of the electric motor and the main winding of the single-phase hood convex motor both use centralized winding.
Centralized windings usually have one coil per ji, but there are also cases where a hidden ji form is used, such as frame type covered ji motors, which use one coil to form two ji motors.

Distributed winding
The stator of a distributed winding motor does not have a convex shape, and each magnetic coil is composed of one or several coils embedded and wired according to a certain rule to form a coil group. After being energized, different magnetic coils are formed, so it is also called an implicit type. According to the embedding
Due to different wiring arrangements, distributed windings can be divided into two types: concentric and stacked.

Concentric winding
Concentric winding is a coil group consisting of several coils with similar shapes but different sizes, embedded in a zigzag shape at the same center position. Concentric windings can be formed into dual plane or tri plane windings according to different wiring methods. Generally single-phase

The stator winding of electric motors and some three-phase asynchronous motors with small power or large span coils adopts this type.

Stacked winding
Stacked windings are generally composed of coils of the same shape and size, with one or two coil edges embedded in each slot, and evenly distributed by stacking them one by one at the outer end of the slot. Stacked windings are divided into two types: single-layer stacked and double-layer stacked. every

A single-layer stacked winding, also known as a single stack winding, is a winding with only one coil edge embedded in the slot; When two coil edges belonging to different coil groups are embedded in each slot, they are placed in the upper and lower layers of the slot, forming a double-layer stacked winding, also known as a double stacked winding. According to the embedded wiring method

With different variations, stacked windings can also be derived into cross type, concentric cross type, and single and double layer hybrid types. At present, the stator winding of three-phase asynchronous motors with high power generally adopts a double-layer stacked structure; Small motors, on the other hand, often use single-layer stacked models

The derivative type in the winding is rare, but single-layer stacked winding is rarely used.

Rotor winding
The rotor winding of asynchronous motors can be divided into two types: squirrel cage type and winding type.

Rat cage type

The squirrel cage structure is relatively simple, usually made by pouring aluminum water into the rotor iron core groove and casting the end rings at both ends; It is also possible to embed copper strips and then weld copper end rings. In order to improve the starting performance, the squirrel cage type can also be made into special types such as deep groove type and double squirrel cage

Type.

Winding type

The wound rotor winding is the same as the stator winding. In addition to the various types of windings mentioned above, it can also use waveform windings. The waveform winding is composed of a single or several turn rod-shaped unit coil, which is embedded and welded into a single wire at the end by two components

The wiring principle of the winding is different from that of the above-mentioned winding, but its appearance is similar to that of a double-layer stacked winding. Waveform winding is commonly used in the rotor winding of large AC motors and the armature winding of DC motors.