Trouble-shooter’s Guide to Motor Overload

Do you know what to do when a motor overloads and may cause tripping of the related electrical circuits? In such a case, the correct prognosis of the problem is the most important. You must primarily identify the root source from where this defect may have originated and the reasons that may have triggered it off.
It is critical to understand the load on the motor, the kind of drive you are dealing with, and whether the motor itself is malfunctioning and could be the culprit.

The Identification Process

Some of the key areas that could be responsible for motor overloads that may need further investigation are:
  • It is possible that there is a mechanical overload on the motor that may cause repeated tripping and even damage to the electric motor winding. In this case, it is important to reduce the load as quickly as possible as buying a new motor can be an expensive proposition and will add to the operational costs.
  • The main source of power to the motor must be shut off immediately in order to conduct an inquiry to identify the exact reason for the tripping. It is also beneficial to make sure that the overload relay system is adjusted correctly. Generally, this is set at 110% of the total power capacity of the motor.
  • In many cases, the drive components may need to be suitably aligned with the motor to avoid any mishaps of this nature.
  • The exact voltage that is being supplied to the motor must be checked on a regular basis, including the possibility of loose contacts that can result in tripping or blown fuses.
  • The actual source of the trip point of the relay must be located and replaced, if found defective.
  • The electrical wiring to the motor must be verified to ensure that all the connections are made in accordance with the requirements. In case of a single or open phase, all the different combinations available must be checked to make sure that all the connections are in order, especially, the red to blue, blue to yellow, and red to yellow phases.
  • Use a clamp on the meter to check the amps when the motor is running to identify if there is an overload occurring. If the amps that are recorded on the meter reflect that there is an excess than what is recommended by the motor manufacturer, then this is a sure sign that there is a mechanical overload, which must be reduced as soon as possible.
  • There may be instances of less amount of power or amps that is getting to the motor and yet tripping occurs. This is a sure sign that there is a defect in the motor.

Other Related Areas and Their Remedies

Once the correct diagnosis is made in identifying the root problem, more than half the battle is won. However, it may be required to continually check on the future voltage that is being supplied to the motor. In a three phase motor, which are most commonly used for commercial purposes, the amount of power drawn by a motor must be equal from all the phases. Any imbalance can cause a problem. If there is an imbalance of more than 10% between any of the phases, the reasons could be several, which must be located and set right immediately to avoid further mishaps.
In some cases, when a new motor is installed, it may refuse to operate. The most obvious reasons could be wrong wiring of the motor or a problem with the motor itself. The cause of this malfunction has to be established quickly and a suitable remedy found. There can be instances when the motor has been running, but refuses to start on another occasion. The reason for this could be that the circuit breaker or fuse tripped on account of an overload or the motor went to the ground and got shorted.
The other reasons that could be behind a motor failure are voltage fluctuation (mostly low voltage), a failed capacitor, or a damaged stator. Worn out bearings can also be a cause and must be replaced on detecting the problem.
Whatever may be the reasons for your motor to be overloaded, it is essential that you get to the root of the problem at the earliest to avoid further complications and avoid the resulting increase in costs that can seriously make a dent in your balance sheet.

Author: Jeson Pitt works as a sales representative for D&F Liquidators, a leading supplier of electrical products. He has a keen interest in everything “electrical” and loves to learn about new techniques to polish his electrical skills and knowledge. Jeson also loves to share his knowledge while enlightening people about electrical products and solving their electrical dilemmas. He lives in Hayward, CA, and can be contacted by e-mail if you have any electrical problems that he can solve.