Here are the final 4 reasons why advanced plastics are better than aluminum and steel in EC Motor applications. Check out our first installment of Why EC Motors are Plastic here.
Refrigeration systems are harsh places because they are subject to constant temperature swings and moisture. This makes corrosion is a major issue and often the reason for motor failure. The combination of temperature changes with water can cause corrosion even in normally non-corrosive metals such as aluminum. Corrosion is worsened by combining several metals, such as steel laminations and bearings with aluminum housings (known as: electrolytic corrosion). Plastics do not corrode, and since they are electrical insulators they also prevent electrolytic corrosion between metal parts attached to them, avoiding motor failures.
6. Vibration and Sound Isolation
No one wants to hear a noisy motor in a convenience or grocery store because a bottle cooler or commercial refrigerator is loud. Plastics are less stiff than metals and have some internal damping. This minimizes the transmission of motor generated sound and vibration, particularly high frequency noises. It also helps protect internal components from shock and impact.
Since EC Motors are subjected to high operating temperatures we only specify fire-retardant grades of engineering plastics for our EC motors. There are several levels of fire retardance as defined by international standards, of which the highest are V-0 and 5-V. All advanced plastics used by Wellington in its ECR motors are V-0 or 5-V rated.
Most of us think that metals are normally stronger than plastics. However, with modern engineering plastics, the difference is no longer large. For example, glass reinforced nylons can have a failure stress of over 200MPa, which is similar to the yield strength of common aluminum alloys and cast or wrought irons.
So what’s the takeaway? Most of the EC Motors on the market have converted to plastic housings and some internal components already. Remember that all plastics are not the same and you want to ask the tough questions on the front end before you find out that the EC Motors you bought because you initially thought they were cheaper, ended up costing you a lot more in the long run. Make sure your manufacturer is transparent and knowledgeable. And don’t be afraid to ask why types of plastic they use to make their EC Motors. If they don’t know, keep looking!
A special thanks to our guest writer: David Howell, Chief Technical Officer, Wellington Drive Technologies, Limited. David holds a PhD in Motor Design and Engineering and has several patents in the field. He leads a team of the brightest motor design and controller engineers in the world in Auckland, NZ. For more information, visit: www.wdtl.com
Did you know the U.S. Department of Energy recently passed regulations that affect commercial refrigeration? These new standards are going into effect within a few short years! We've put together a FREE helpful eBook that will help explain the guidelines and how they will affect your business. Just click the link below to download!