There are a myriad of issues that can cause electric motors to fail. However, among this rogue’s gallery of problems there is a set of usual suspects that crop up more often than the others. Jonathan Wilkins compiles a list of the top five causes.
Excessive heat is one of the biggest killers for electric motors; this is the granddaddy of motor issues. In fact, the other four items on this list are often damaging precisely because they contribute to excess heat generation.
The oft stated rule is that the life of the motor winding insulation is halved for every 10 degrees centigrade of additional heat to the windings. Because of the excessive levels of deterioration that entails, keeping your motors running at optimum temperature is one of the best ways to extend their life.
Dust and contamination
Particles suspended in the air will find their way into an electric motor. Once inside, the damage they cause depends on the type of particle. If they are abrasive they will wear down components, while some particles are electrically conductive and can interfere with currents across components. Lots of these particles blocking cooling passages will also contribute to overheating. Naturally, selecting the right level of IP (Ingress Protection) can help with this to a certain extent.
Power supply Issues
Harmonic currents caused by high frequency switching and pulse width modulation can lead to voltage and current distortion, overloading and overheating. All of these factors reduce the life of the motor and its components and increase long-term equipment costs – but that’s only one issue. Power surges cause their own problems as do over- and under-voltage. Managing these issues is a task that requires constant attention and care.
Humidity and Moisture
By themselves moisture and humidity contribute to the corrosion of components, but when coupled with particles from the air they can create a deadly combination for a motor. Certain particle contaminants can combine with moisture and create even more damaging solutions, shortening the life of motor components even further.
The problem with correct lubrication is that it’s a balancing act that can be very difficult to achieve. Just like Goldilocks and the three bears, there are multiple options to get it wrong and only one way to get it right. Over-lubrication and under-lubrication both pose problems, but there can also be issues with contaminants in the grease, or the use of a lubricant not suited to the task at hand.
It is worth remembering that these problems are all interrelated, tackling only one of them won’t necessarily solve the problem. All of them also have one thing in common; they can be avoided with correct motor usage and maintenance as well as environmental management.
When European Automation buys a motor for future re-sale, we ensure that these problems are no longer affecting it. However, you should be aware that the European Design Directive puts a limit on the amount of repair work you can do without beings considered to be ‘introducing a new product to the market’, rather than repairing an existing one.
Jonathan Wilkins is with European Automation