Motor Winding Explored

Most mining, commercial, industrial, and military machines use electric motors as a critical part of their production and manufacturing. However, at some point all motors will need to be repaired or replaced. Understanding the mechanical basics of motor rewinding will help you make the best decision on which is required.  An armature winding process helps to regain the full function of an older motor for a few more years. 

Three phase asynchronous motors are the most commonly used motors in the world due to its dependable efficiency and low manufacture and maintenance costs. 

The motor has two main parts: the rotor and the stator. The rotor is usually made as a squirrel-cage, and it is inserted in the stator’s hole. The stator is made out of iron core and winding.

The stator is used to generate magnetic fields. Rotation of the magnetic field “cuts” the squirrel-cage, where it induces voltage, and as the cage is short-circuited, the voltage generates a flow of electric current. This current in the magnetic field generates force.

When the motor fails then you are faced with two options

Old winding

1. Rewind – This is where you opt to rewind the failed motor back to its original efficiency, or to rewind it to a higher efficiency.
2. Replace – This is where you opt to replace the failed motor with the same efficiency motor or to replace it with a higher efficiency motor.

Motor rewinding methods can be divided into three steps: 

1. Coil removal 
2. Winding new coils 
3. Varnishing the stator

Motor Rewinding Methods

There are two schools of thought / methods used to rewind motors: traditional armature winding, and the alternative, or mechanical method. Traditional techniques generally last longer, while the alternative approach might be faster. 

The Traditional, Manual Method of Motor Winding

The generally preferred traditional motor winding method requires that the previous phase is complete before starting the next phase. This can take several hours. Traditional techniques require higher operating temperatures and thus a higher insulation class rating. 

Higher operating temperatures typically increase pressure on the mechanical components (such as bearings). 

However, a reduction of the end turns for I2R stator losses can be easier with the traditional method, as opposed to the mechanical rewind (alternative) method.

The Alternative, Mechanical Method to Armature Winding

The alternative methods are faster but need additional and more expensive equipment to complete. However, this may be a desired alternative if the goal is potentially better slot filling. 

This method incorporates a cold coils removal process, and while this may eliminate the risk of core damage due from high temperatures during burning out (traditional method), it does not remove the possibility of increased motor losses. 

Additionally some types of epoxy varnishes need a very strong force to remove the coil, which raises the risk of core mechanical damage. This is why it is generally preferred to use a traditional burnout process in the oven, with controlled burnout temperature, over the cold coils removal process (cold stripping).

The Benefits of Rewinding a Motor

Reputable, skilled motor rewinders in Cape Town are in high demand. This is because motor rewinding is always a more cost effective solution when it comes to the high costs of replacing a failed motor with a new one. Additionally, rewinding a motor boosts efficiency and is shown to increase equipment performance.

As long as you have an experienced engineer by your side, you are assured of seeing your equipment returned in tip-top shape. 

Ask CAW for Motor Rewinding Today!

So, whether you decide to refurbish an old motor, rewind it, or replace it entirely, trust the experts at CAW to replace, rewind and repair your old motor with care, expertise, and precision. With over 50 years in the industry, we are ready to help you.