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July 05, 2018
4 minutes to read  

Comparing Shaded Pole, PSC and EC Motors

We write a lot about electronically commutated motors, sometimes called EC Motors or ECM. But what's the difference between EC motors and other traditionally used motors like shaded pole motors or permanent split capacitor (PSC) motors? How much will those differences cost you and more importantly, save you? Let's spend a few minutes comparing shaded pole, PSC and EC motors.

Shaded Pole Motor

This trusty motor is your standard single-phase AC induction motor. There's nothing terribly sophisticated about a shaded-pole motor. They're usually single speed, low horsepower motors used for things like light ventilation. While it's the least expensive of the three types of motors, at 30 percent efficiency, it's also the least efficient. Here's an excellent description and graphic from Electrical 121 website



Permanent Split Capacitor Motor (PSC)

Where a shaded-pole motor is considered old design and old technology, a PSC motor is more middle of the road. Because of their widespread use in HVAC/R applications, PSC motors are probably the most common type of motor. A PSC motor has a capacitor that helps run the motor and helps give it more torque or force. The construction is more sophisticated than a slotted pole motor with slotted windings inside the stator (the stationary part of the motor's rotary system.) PSC motors are able to run at single or multiple speeds, depending on the application. But at 40 to 60 percent efficiency, they're nothing to write home about. Here's another Electrical 121 explanation and diagram:



Electronically Commutated Motor (EC or ECM)

The EC motor is considered a 'Smart' motor because of the use of technology to make it run. EC motors are equipped inside with a printed circuit board (PCB) and logic control to know when to turn on or when to apply more or less power. The windings are separated, the rotor is usually steel or rare earth magnet material (permanent magnet material). The attached PCB allows the motor to receive feedback from the environment. If it picks up air resistance, for example, it may increase speed. EC motors typically include more plastic materials, which has significant added benefits in terms of cost, performance and durability. You can expect an EC motor to achieve 70 to 83 percent greater efficiency over shaded pole or PSC motors. EC motor sales are increasing year over year, but they haven't caught up to PSC motors yet. 



Cost vs. Savings

Let's talk price. It's quite simple really. The lowest-cost option is the shaded pole motor. You can expect to pay two times more for a PSC motor, and two times more for an EC motor. But... because of the efficiency of the EC motor, you can also expect to see the return on your investment within a year. That might not sound like much if you're talking about one motor, but what if you're talking about hundreds of motors running refrigerator cases in stores all over the United States? That kind of savings, coupled with a quieter, cooler, more energy efficient motor would be worth a second look.

The U.S. Department of Energy thought so. In 2014, the DOE released new energy efficiency guidelines addressing the amount of energy consumed by commercial refrigerators, freezers, reach-in coolers, and bottle coolers currently used in supermarkets, restaurants, commercial kitchens and convenience stores. The standards went into effect in 2017 and will reduce energy consumption by

  • +40 percent for solid-door "reach in" refrigerators and freezers.
  • Nearly 30 percent for glass-door supermarket refrigerator cases.
  • +10 percent for freezer cases. 

The DOE guidelines stated that these reductions were achievable as companies did three things: 

  • Installed LED lighting with sensor technology.
  • Installed glass doors with more insulation.
  • Installed high efficiency electric EC motors.

EC motors are an excellent choice for any company that's looking at the big picture. Smart technology is here to stay and is only getting more sophisticated, not less. EC motors can save money not just because it operates efficiently, but because they are programmable, and can reduce the number of SKUs you need to purchase. 


So that's our quick comparison of shaded-pole, PSC and EC motors. And here are a few more posts on the topic if you'd like to learn more:




Filed Under: EC Motors