The Basics of EC Motors

The Basics of EC Motors

 

What are EC motors?

EC (Electronically Commuted, or Electronically Controlled) motors are electric motors which have permanent magnets on the rotor and use electronics to control the voltage and current applied to the motor.

How do they work?

All electric motors work by the interaction of two magnetic fields pushing on each other. One field is created by the rotor and one by the stator. The difference between motor types is in how these fields are created and controlled:

  • EC motors use permanent magnets to create the rotor field, and a series of coils controlled by an electronic controller (or "commutator") to create the stator field.
  • Brushed DC motors use permanent magnets to create the stator field, and a series of coils powered by the DC input voltage and controlled by mechanical contacts ("brushes") to create the rotor field.
  • Induction motors use a series of coils powered and controlled by the AC input voltage to create the stator field, and the rotor field is created electromagnetically (or "induced") by the stator field.

EC motors have no brushes, so avoid the sparking and short life of brushed motors. Because they have electronics controlling the stator, and do not need to waste power inducing the rotor field, they give better performance and controllability, and run cooler than induction motors (for small motors, at least: high  horsepower 3 phase induction motors can be very efficient). EC motors are used today in many fractional-horsepower applications where high motor efficiency, reliability, and/or controllability is desired.

I hear many terms used for electronically controlled motors, like EC, ECM, BLDC, PMSM, and VFD. What is the difference?

Terminology in the motor world is confusing, as many acronyms are used for the same thing, and people's definitions are not always consistent. For all practical purposes, many of these terms are interchangeable. 

  • EC stands for Electronically Commutated.  ECM stands for Electronically Commutated Motor. These are the same thing, and usually refer to motors which use AC mains power.
  • BLDC stands for Brushless Direct Current motor: a BLDC motor may be the same as an EC motor, but it is more often used to refer to an electronically controlled motor which uses a DC power supply.
  • PMSM stands for Permanent Magnet Synchronous Motor: often this means the same thing as a BLDC motor, although in academic circles the two terms are sometimes used to distinguish between motors with different types of commutation algorithms.
  • VFD, which stands for Variable Frequency Drive, is the one term which means something significantly different. A VFD is a type of electronic controller which is used to give an induction motor (usually a larger 3 phase motor) improved controllability and part-load performance. Although VFD electronics are similar to those of an EC motor controller, the software is quite different and the two are not interchangeable.

What are the advantages of EC motors?

EC motors are very high efficiency, and maintain a high efficiency level at part speed. This means that in most cases they use from less than one third to one half of the electricity used by the traditional "shaded pole" induction motors used in the ventilation and refrigeration industries, which in turn translates into lower operating costs and short payback periods.

EC motors’ high efficiency also means that the motors run “cool”, and dramatically reduce the amount of waste heat produced. Reduced waste heat at the evaporator motor level also typically results in reduced operation at the compressor level, which allows further energy savings. Further, running cooler improves the life of highly loaded motor parts like windings and bearings.

EC motors also have a wider operating range than traditional induction motors, which means that one ECM motor can replace a number of induction motor models. In this way, the number of models required by a typical customer is significantly decreased, which decreases and simplifies inventory. This is the main reason why ECM product lines usually include less motor models than their induction counterparts.

In terms of speed control and features, because the motor’s operation is controlled by software, EC motors allow customers to optimize and integrate the motor, fan and controller with the application, and to include features like data communications, constant volume control, variable speed, etc.

EC motors are also quieter than traditional inefficient motors, have longer design life and require less maintenance.

What is the efficiency difference between a shaded pole, permanent split capacitor and EC motor?

Efficiency will vary depending on the manufacturer, power rating and load conditions.  However, as a general rule of thumb, shaded pole motors range from 15-25% efficiency, permanent split capacitor motors range from 30-50% efficiency and EC motors achieve 60-75+% efficiency.

I need to increase the efficiency of my product for upcoming DoE regulations. How much will EC motors help me?

After the compressor, refrigeration fans are one of the highest energy consumers in an HVAC or refrigeration product. Improving motor efficiency by moving to EC motors is one of the most cost-effective "bolt on" efficiency upgrades available, offering similar "bang for buck" to changing to LED lighting. On a typical glass-front upright integral (plug-in) cabinet, upgrading to EC motors can improve system efficiency by 20-25%.

The use of hydrocarbon refrigerants is becoming more popular. Are EC motors suitable for use with hydrocarbon refrigerants?

Not all EC motors are suitable for use with hydrocarbon refrigerants, or for use in all applications. Wellington offers "HC compatible" versions of our ECR refrigeration fan motors, which are "non-sparking" per UL requirements, and approved for use with hydrocarbon refrigerant charges up to 150gm. For more safety-critical applications we also offer ATEX certified (EEx nA IIA T5) versions of ECR motors. For assistance in selecting the correct motor for your hydrocarbon application, please contact us.

What is the payback period for replacing my shaded pole or permanent split capacitor motors with EC motors?

Payback analysis involves many factors such as your local electricity rate, duty cycle of the motors, efficiency of the air mover and operating conditions.  For high duty cycle applications such as refrigeration fans, payback can be as short as a few months, while for low duty applications, energy savings may not be the driver for moving to EC motors.  We’d love to hear about your application so please contact us to discuss your application.

I hear that EC motors are expensive.   What is the price premium vs. my current motors?

EC motor pricing will vary by features, size and volume.  In general you can expect to pay anywhere from 2-4x the price of an equivalent size AC motor.  Our products are very competitively priced and we’d love to hear about your application so please contact us to discuss your application.

Do you offer EC motors that are dual voltage (a single motor P/N can accept either 115 or 230 VAC)?

Yes, our ECR2 series motors are dual voltage compatible and accept any voltage from 70-264V, 50-60Hz, 1ph, under a single P/N.

Can your EC motors reverse to blow dirt out of my condenser?

Yes, our ECR motors are available in timed reverse on stop, timed reverse on start, or continuously reversible versions, and custom programmed behaviours are available for volume customers.

My AC motor runs 10-15% slower with 50 Hz mains than with 60 Hz, which creates a performance issue in my application.  Can I expect the same RPM loss at 50 Hz with EC motors?

No.  Because EC motor electronics convert the incoming 50 or 60 Hz AC power to a DC voltage within the motor, the speed of the motor will be exactly the same with 50 or 60 Hz AC power input.

I need to have the flexibility to adjust motor speed in the field to adjust to the application conditions. Do you have any EC motors that are field programmable?

Yes, our ECR2 motors are field programmable from 300-1800 RPM in increments of 50 RPM with our programming tool.   Used in conjunction with our SCS controller, we can change fan speed in real time to maximize the energy savings in your system.

My AC motors “hum” and are very hot to the touch when I reduce the speed.  Do EC motors also have this humming noise and get hot when the speed is reduced?

No. The “hum” you are hearing is likely the noise produced from resonance of the motor lamination stack when you speed reduce an AC motor with a TRIAC, voltage chopper or some other phase chopping device.  The noise tends to become more prevalent the further the speed is reduced.  The heat generated from altering the sine wave to a chopped waveform will also create additional temperature rise in the motor leading to shorter motor lifetime. 

What sizes of EC motors can Wellington supply?

Our current EC range includes motors from 2-25W (1/375-1/30 hp) output power, in packages compatible with Q frame and unit bearing refrigeration fan motors. Products coming soon include C-frame compatible EC motors from 1-5W and 95mm frame EC motors up to 125W 1/6hp. See our fans and motors page for more information,

I like EC motors but I'm not ready to convert my whole range. Can Wellington supply my non-EC motor needs too?

Yes we can. We supply Q frame shaded pole motors under our AirMoVent brand, and can source a wide range of customised fractional horsepower induction motors. See our fans and motors page for more information.


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