4 main electrical problems in industrial motors

Having a preventive maintenance programme is the best way to monitor the health of an electric motor, as it allows us to identify, evaluate and resolve problems that arise over time and may require a repair service, which in turn results in increased costs.

Electric motors are complicated and complex equipment. Therefore, they can stop working for many reasons. Both AC motors and DC motors can develop similar problems. Whether due to lack of maintenance, wear and tear or simply old age, failures occur due to various causes.

In this respect, the main electrical problems in industrial engines can be classified into four basic categories:

• Voltage unbalance effects,
• Effects of single-stage operation,
• Overload effects, and
• Environmental and maintenance effects.

But let's look, in detail, at each and every one of these electrical problems in industrial motors that we might encounter in our installation:

• Electrical problems in industrial motors: Voltage unbalance effects

  There is a good deal of literature on the subject of voltage unbalance and associated current unbalance. In general, it can be stated that when voltages are unbalanced, higher induced currents are present in the rotor, because it has a lower impedance to the negative sequence voltage components.

  For example, for a voltage unbalance of 3%, the current unbalance can be from 18% to 24%. The increase in stator current is usually small, therefore, the overload protection does not operate in time to protect against damage due to the high induced current in the rotor. This additional heat in the rotor can be present for a considerable period of time, and because the rotor laminations and rotor shaft constitute a continuous metallic element, this heat is transmitted to the bearings, reducing the life of the bearings.

  Voltage unbalance problems can occur from the power supply network to the industry or facility, or in the plant or industry's own distribution system. The potential problems are as follows:

  • Potential problems in the power supply network. These problems have to do with voltage unbalance on the line, reduced use of transpositions on the lines, open deltas in the transformers, situations causing voltage unbalance effects, specifically stator heating (missing winding) and rotor heating (problems with vibrating bearings, etc.).
  • Potential problems in the plant's own distribution system. From large single-phase loads, unbalanced lighting loads, different impedance of conductors, blown fuses in one phase of a capacitor bank for power factor correction and expansions without the required additional capacity. This causes effects such as voltage unbalance, i.e. stator heating (winding failure) and rotor heating (problems with bearings, vibrations, etc.).
• Electrical problems in industrial motors: Effects of single phase loss

  The potential effects that single-phase loss can lead to are similar to those produced by voltage unbalance; however, single-phase loss represents one of the worst cases of voltage unbalance. Additionally, excessive overheating occurs in the windings of the two phases that remain in operation. Phase unbalance occurs when the supply lines are out of phase or “out of phase”.

  Naturally, unbalance in three-phase motors occurs when single-phase loads are applied, which causes one or two of the lines to carry more or less load. Three-phase loads in three-phase installations are balanced from design and installation. Unbalance begins when additional single-phase loads are added to the system. This unbalancing results in the three-phase lines not being 120 “electrically” out of phase in their currents and voltages, and in the three-phase motors operating at higher temperatures than those indicated as nominal values.

  A three-phase motor operating in an unbalanced circuit cannot deliver its rated potential, so degradation factors must be applied. This generates potential problems in the power supply network, i.e:

  • Loss of a phase in the supply network.
  • Fuse blown in one phase of the supply network.
  • Fault in one phase of the supply line.
  During the loss of a phase, there is excessive heating in the windings of the remaining phases and heating in the motor (motor rods and problem with bearings and lubricants).

• Electrical Problems in Industrial Motors: Effects of Overloads

  Most of the problems caused by overloads are only reflected as overheating in the stator, while two problems, repeated starts and repeated stops, also cause mechanical stresses on the heads of the individual nozzles and nozzles.

  These mechanical forces generated via the process of motor operations (start-stop, etc.), are reflected as physical stress on the coil heads and terminals of the copper coils, increasing the potential problems due to fracture of the insulation of the conductive parts.

If you are interested in finding out more about electrical problems in industrial motors, we invite you to learn more about how to detect signs of mechanical failure in industrial equipmentas well as to subscribe to our Newslettera newsletter that provides you with technical content about the best technological solutions for industrial plants, focused on automation and maintenance.