All electric motors have their predetermined life span, typically ranging from 30,000 to 40,000 hours. However, this is dependant on proper maintenance – without which they are likely to break down much quicker. Understanding the top five cuases of motor failure, as well as the steps that can be taken to reduce the risk of these failures occurring will give your motor the best chance of achieving its maximum possible service life.
1. Electrical Overload
Electrical overload or over-current is caused by an excessive current flow within the motor windings, exceeding the design current which the motor is able to carry efficiently and safely. This can be caused by a low supply voltage, resulting in the motor drawing in more current in an attempt to maintain its torque. It can also be a result of short circuited conductors, or an excessive voltage supply.
Possible solution: Electrical overload can be prevented by installing effective over-current protection which will detect overcurrent and interrupt supply.
2. Low Resistance
The most common cause of motor failure, and arguably the most difficult to overcome, is low resistance. Low resistance is caused by the degradation of the insulation of the windings due to conditions such as overheating, corrosion, or physical damage. This leads to insufficient isolation between the conductors or motor windings, which can cause leakages and short circuits, and eventually motor failure.
Possible solution: The insulation should be regularly inspected for signs of wear, and replaced before low resistance is able to cause failure.
Around 55% of insulating failures in motors occur due to overheating. Overheating can be caused by poor power quality, or a high temperature operating environment. For every 10oc that the temperature of a motor rises, the insulation life reduced by 50%.
Possible solution: It is critical that the motor is kept as cool as possible, ensuring the operating environment is kept cool if possible will help prevent breakdowns.
Contamination from dust, dirt and chemicals is one of the leading causes of motor failure. Foreign bodies which find their way inside the motor can dent bearing raceways and balls, leading to high levels of vibration and wear. It can also block the cooling fan, limiting the motor’s ability to regulate its temperature, and increasing the likelihood of overheating.
Possible solution: Preventing contamination is relatively easy. Keep work areas, tools and fixtures as clean as possible to help eliminate the chance of contamination entering the motor. Also, when laying out the workspace, try to position motors away from grinding machines which produce large amounts of contaminants.
Vibration can lead to many issues with the motor, and can eventually cause the motor to fail prematurely. Vibration is often caused by the motor being positioned on an uneven or unstable surface. However, vibration can also be a result of an underlying issue with the motor, such as loose bearings, misalignment, or corrosion.
Possible Solution: Motors should be checked regularly for vibration, using a motor analysing tool such as the SKF EXP4000 Dynamic Motor Analyser. In order to reduce vibration, ensure that the motor is positioned on a flat, stable surface. If vibration still occurs, check for signs of wear, as well as loose bearings or misalignment. Consider contacting a specialist if the source of vibration cannot be identified.