Electric motors must operate reliably in a wide variety of environmental conditions, from hot and dusty mine sites to arctic oil rigs. In some regions, the seasonal weather can change quickly and bring about extreme temperatures that can severely impact motor performance. It's essential to understand what these impacts are and what you can do to prevent interruptions to your operations and productivity.
Electric Motors and Temperature
Typically, electric motors are designed to operate within a temperature range of -20 to 40 degrees Celsius. Outside this range, several issues arise that, left unchecked, can reduce your motor's service life and cost you and your business a lot of money. Even if the ambient temperature isn't outside this range, other factors that affect the motor temperature can stack up to push it beyond its rated limits.
Before dealing with the specific problems brought about by extreme weather, make sure that you've done everything you can to keep your motor temperature under control. Ensure that the motor is the correct size and that it is not excessively stressed during start-up. If you have a substantial starting load, you may need to use a soft starter to keep inrush currents from overheating the windings and damaging the motor. Keep the motor clean and dry with plenty of access to cooling air, and, if possible, installed in a sheltered and climate-controlled space.
Depending on the application, achieving the best operating conditions for the motor might be difficult. Here's what to do in a less-than-ideal scenario.
Take Care of Your Bearings
Bearings withstand an incredible amount of friction and stress during motor operation. It's vital to ensure that the lubrication, whether it's grease or oil-filled bearing, can do its job. Cold temperatures increase the lubricant viscosity, causing grease to become thick and tacky, leading to uneven distribution and hotspots of increased friction and wear. If the lubricant gets too hot, it can become thin and runny, reducing the protective lubrication layer's thickness and potentially becoming damaged by oxidation.
When you know your bearings will experience extreme temperatures, the first thing to do is select the right lubricant. There are specialized high- and low-temperature greases and oils formulated to maintain normal viscosity over a more comprehensive temperature range. By choosing bearings that use them, you can achieve a far longer service life for your motor.
If the motor is exposed to freezing temperatures, take care to start it up slowly with a minimal load to give the bearings a chance to warm up and distribute the lubrication. For larger motors with oil-filled bearings, a sump heater can be used to keep lubrication warm and fluid. When motors are stored away or used intermittently in sub-zero conditions, periodically rotate the shaft, or operate the motor as part of your regular maintenance schedule to keep the lubrication evenly distributed within the bearings.
Prevent Motor Overheating
In extremes of both hot and cold weather, overheating can become a problem for electric motors. When ice or dust builds up on the motor's body and ventilation ports, the internal temperature rises quickly from the insulating effect and inadequate cooling airflow.
To prevent this, keep the motor shielded from the weather and any direct sources of pollution, which can create an insulating layer that heats the motor and can work its way into the bearings. Make sure the motor body is clean and free of ice before starting it up, and pay special attention to ventilation ports, fans, and cooling fins to ensure that they are not blocked or impeded in any way. When operating motors outdoors in hot weather, take care to shield them from direct sunlight, and make sure the vents are not covered up and have access to plenty of cooling air.
If the ambient temperature is extremely hot, make sure that the motor components and wiring have the correct NEMA insulation class. Insulation around cables and connections, as well as the motor windings, will quickly break down and fail as the motor starts to overheat, so having a motor made of heat-resistant materials will go a long way toward keeping it up and running in a hot environment.
Prevent Motor Condensation
When an electric motor experiences rapid cooling, such as when it's switched off in freezing temperatures, the motor body's exposed surface cools faster than the windings, which causes condensation to form inside the motor. This can be very detrimental, causing corrosion, short-circuiting, and power loss in the windings. Because this happens internally, spotting the problem and dealing with it in time is difficult, so prevention is vital.
Totally Enclosed, Fan-Cooled motors (TEFC) are typically not airtight, and they can still draw in moisture-laden air during cooldown. Your TEFC motor must be fitted with a drain plug positioned underneath so that condensation can be allowed to run out regularly. If motors are to be stored or used intermittently, fitting a space heater inside will prevent most condensation from forming, keeping the motor interior clean, dry and corrosion-free.
Check Your Fans and Seals
Because they're typically made of plastic or rubber, cooling fans and port seals are the parts of a motor that are most susceptible to becoming brittle and cracking during cold weather spells. If your motor is operated in freezing weather, consider using metal fans and alternative, cold-resistant materials for seals, such as silicone instead of neoprene.
Explosion-proof motors are designed to withstand an internal explosion of specified material and prevent it from igniting flammable gases and vapours in the vicinity, protecting your infrastructure and personnel. They are mandated in industries such as petroleum, where motors operate in high-risk environments.
In cold conditions, explosions produce a substantially greater pressure inside a motor, rupturing seals and spreading the blast to the surrounding area. Check that your explosion-proof motor's rating allows for temperatures as low as it will face in its intended operating location.
Keep Out Rodents
Suppose your motor is operated in an isolated area without much activity, in colder seasons, or is exposed to a rapid weather change. In that case, it can bring in rodents, which are attracted to the warmth radiated by the motor. They can chew through cable insulation and damage rubber and plastic components, causing damage to infrastructure and increasing the electrical fire risk.
Once rodents are established on the premises, it can be challenging to remove them, so use preventative measures. Periodically spraying down areas with repellent and placing traps will go a long way toward keeping them at bay, and your equipment in good working order.
Extreme weather changes don't have to cause you headaches and interrupt your operations. With the right preventative measures and routine maintenance, you'll be able to keep your motors running reliably in all weather conditions.