AC Motors – Rewind and Repair

AC Motors are everywhere, from household appliances such as water pumps and refrigerators to industry equipment such conveyor belts, right through to pumps on Navy warships. AC motors are electric motors which are driven by an alternating current (AC) as opposed to a direct current that drives DC Motors.

An AC motor generally consists of two parts – an outside stationary housing, with the stator being made up from coils in the form electromagnets arranged on the outside of the motor. This is supplied with an alternating current to produce a rotating magnetic field. The second rotating magnetic field in made up of an inside rotor, solid metal axle, loop of wire, coil and squirrel cage constructed of metal bars and interconnections attached to the output shaft.

Common Failures in AC Motors

AC motors have the potential for a very long life, due to the fact they have no common wear parts such as brushes and commutators – being fairly low maintenance, routine inspections are often neglected for AC motors. There are a few inspections you can carry out if your motor fails or experiences underperformance:

• If the motor can be removed from its drive then check whether or not the shaft can rotate by hand without difficulty – if it is strenuous, it could be a sign of a mechanical obstruction or failed bearing.
• Look for any initial, obvious signs that the motor may be damaged. These include broken mounts, signs of burning or carbon and contamination from water, oil, grease or rust.
• Disconnecting the motor and taking the resistance measurement can indicate if there are shorted coils present – the expected results should be available in your motor manual or from the manufacturer.
• Taking the insulation resistance (IR) between windings, the majority of winding faults are due to IR. Typically, the IR should value should be a minimum of 2M ohms and a maximum of 100M ohms. A value of fewer than 2M ohms indicates that the insulation is deteriorating or has already failed.

To prevent experiencing these problems, consider a maintenance contract for fixed term contracts and advice on how to best maintain and get the most out of your motor.

Repair or Replace?

If a motor does fail, companies may experience downtime on production – which can be costly. When faced with this problem, businesses must decide between repairing, rewinding or replacing their motor, here are a few things to consider when making this decision:

• Age of the motor – if your motor is old, it could be the case that replacing it with a newer, more energy efficient motor will save you money in the long run. However, dependent on what the problem is, replacement is likely to be a much bigger investment than a rewind or repair.
• Use of the motor – The more horsepower a motor delivers, the greater the operating cost. If a smaller motor that is used infrequently begins to underperform, the cost to the business may not be substantial even if the motor is inefficient, in this scenario a repair of the motor can be a cost effective solution. If the motor is a larger one in constant use, the cost of underperformance will soon outweigh the cost of a repair or replacement.
• Time – Downtime of an important motor can be extremely costly for business. Having a motor repaired can take as little as 24 hours whereas acquiring and installing a replacement motor is likely to take longer.

AC Motor Rewinds and Repairs at Mawdsleys

At Mawdsleys, we understand how important a motor can be for your business; That’s why we offer a 24-hour emergency call out service to all our clients.

We manufacture and repair AC and DC motors from our in house workshop – keeping waiting time to a minimum so you can have business up and running again as soon as possible.

If you require a new AC motor or are experiencing underperformance with your current motor, give us a call on 0117 955 2481 or fill out a contact form.