electric motor fault

When a three-phase motor keeps blowing a fuse, it means the current drawn from the circuit has exceeded the protective device's limit. The most common causes are a short circuit, o... More Details

An electric motor usually "burns out" when its windings overheat and the insulation breaks down. Behind this you almost always find overload, phase loss, under- or over-voltage, po... More Details

It is normal for an electric motor to run somewhat warm; a hot frame does not automatically mean a fault. But heat that you cannot touch for even a few seconds, a frame that gets v... More Details

If your three-phase asynchronous electric motor will not turn, the cause usually falls into three groups: a lost phase in the supply (the motor hums but the shaft does not rotate),... More Details

When a three-phase motor will not turn at all, the fault should be narrowed down from the outside in, in order before any part is replaced: first the supply and protection, then wh... More Details

When a three-phase asynchronous motor energises and hums but its shaft does not turn, it means the motor is magnetised yet cannot produce enough starting torque to turn the shaft. ... More Details

If one of the three phases is lost while a three-phase motor is running (single phasing), the motor does not stop at once; instead the current drawn through the two remaining phase... More Details

A motor phase protection relay is a small protective device that continuously monitors the three-phase supply and stops the motor by opening the control circuit when it detects a p... More Details

A motor winding burns out when the heat produced by the current it draws exceeds the limit the wire insulation can withstand. The most common causes are overload, phase loss, low o... More Details

An insulation resistance (megger) test is a basic check that shows how sound the insulation is between an electric motor's windings and its frame (earth). The instrument, called a ... More Details

The winding resistance of a three-phase motor means measuring the copper resistance of the three phase windings — labelled U-V-W — one by one with an ohmmeter (or a micro-ohmmeter ... More Details

When an electric motor vibrates, it reveals an imbalance in the rotating parts or a defect in the system the motor is attached to. The most common causes are unbalance, coupling (s... More Details

A constant hum, a metallic ticking or a thin whistle from your electric motor usually comes from a bearing. Bearing noise is the first sign that the balls and races are starting to... More Details

A motor "leaking to the frame" means the insulation between the windings and the metal housing has weakened, letting voltage reach the body. The quickest symptoms are a tingling se... More Details

If your three-phase asynchronous motor runs the wrong way, the fix is simple: swapping any two of the three phases feeding the motor reverses the direction of rotation. There is no... More Details

A burnt terminal box on an electric motor almost always comes down to a single mechanism: high contact resistance at a connection point. A loose bolt, an oxidised surface, under-ti... More Details

If your electric motor gives off a burning smell, the first thing to do is stop it and cut the supply. The smell is a serious warning that the winding insulation, the bearing greas... More Details

An electric motor draws a certain current from the supply even with no load on the shaft; this is called the no-load current, and in a healthy three-phase asynchronous motor it is ... More Details

The most typical signs of a broken rotor bar are a motor that clearly struggles under load, a slow periodic swing (modulation) in speed and current, weak starting and a gradual los... More Details

Coupling misalignment occurs when the shaft of a motor and the shaft of the machine it drives do not meet on the same axis, and it usually shows up as noticeable vibration. This vi... More Details