Commercial refrigeration efficiency is a hot button issue as government regulatory agencies draft and enforce new energy efficiency standards and end users want more powerful, less energy consuming equipment. As a result, designers of refrigeration products are increasingly eyeing electronically commutated motors as a key path to increased efficiency.

In today’s regulatory environment, OEMs have to be concerned about meeting regulations at the state level, most notably California, and the federal level, both in the near and the longer term.

The U.S. Department of Energy (DOE) is working on a whole range of energy conservation standards for commercial refrigeration appliances. In August, a consensus agreement was announced that covers coolers and freezers with an enclosed, walk in storage space of less than 3,000 square feet that are refrigerated to temperatures above, at or below 32 DegF. The agreement affects products that will be built on or before Jan. 1, 2012.

In 2005, three similar agreements were signed covering a number of commercial products, including large, packaged air conditioners and heat pumps, commercial ice-makers, and commercial refrigerators, freezers and refrigerator-freezers, which the Air-Conditioning and Refrigeration Institute says will save 8,000 MW of peak power by 2020.

Enlarge this picture Direct Electricity Savings (30-in. fan).

According to the DOE, replacing traditional shaded-pole motors with ECM motors is one of the best ways to improve energy efficiency. In the DOE’s report, Energy Savings Potential for Commercial Refrigeration Equipment, the DOE estimates primary energy usage in the commercial refrigeration sector at 990 trillion BTU per year.

The report identifies potential energy savings of about 266 trillion BTU by implementing more efficient technology in equipment such as walk-in coolers (a 58 trillion BTU savings), refrigerated vending machines (56 trillion), supermarkets (53 trillion), beverage merchandisers (29 trillion), reach-in freezers (28 trillion), reach-in refrigerators (24) trillion) and ice machines (18 trillion). Of all the areas for potential energy savings, evaporator fan EC motors offers the greatest potential opportunities for savings. According to the report, energy savings using these types of motors in commercial refrigeration applications could reach 85 trillion BTUs and have a payback of between 6 months and 3 years.

At the state level, the most pressing regulatory action is occurring in California and it mandates that commercial refrigeration appliances use EC motors. “Regulatory pressures have been making product adaptability a key issue lately,” says Tim Neal, Industry Leader for Commercial Refrigeration at GE ECM by Regal Beloit, Beloit, Wis. “Starting January 1, California’s Title 20 appliance efficiency standards will require that all new walk-in coolers and commercial freezers use ECM evaporator fans. With many states referring to Title 20 in their own efficiency rulings, this new standard will quickly become the law of the land.”

Michael Jenkins, sales manager for North American operations for Elco Motors of Quebec, Canada, says that electronically commutated motors, which use brushless-DC technology, are inherently more efficient than traditional AC asynchronous induction motors, in practically any load condition. The higher efficiency mainly is the result of the use of permanent magnets to generate the rotor magnet field. “This solution sensibly reduces magnetic and Joule-effect energy losses against the traditional squirrel-cage rotor,” he says.

The MCE-IP65 EC motor from Elco Motors can drive 6 to 10 in. fans and feature efficiencies of up to 70 percent.

The benefit of improved efficiency is driving many manufacturers toward using electronically commutated motors, says Jenkins, especially on evaporator applications such as display cases for supermarkets, convenience stores and appliances, and especially with remote condensing units, he says. “With these types of products, energy efficiency will payback the additional cost of the motor in such a rapid fashion that most of the new applications are going into energy efficient ECM motors.”

Commercial refrigeration encompasses a wide-ranging product mix that includes everything from large walk-in freezers, to small, refrigerated-display cases, and ice-cream machines to ice-making machines. While as a group these products are lumped together, the particular application will affect the designer’s specification of motors. “This is first of all based on required airflow,” says Armin Hauer, product manager for ebm-papst of Farmington, Conn. “The larger a fan of a given geometry and airflow, the higher the motor torque requirement. Motor torque generally determines the motor frame size.”

According to Hauer, refrigerated vending machines traditionally use 1,550-RPM motors with an output of about 12 W. Refrigerated display cases are usually designed for 7 in. to 11 in. axial fans running at 4-pole speed and require about 16 W shaft power. The smallest walk-in coolers use 10-in. and 12-in. axial fans with 1,550-RPM motors that produce 1/15 HP.

While ECM is the relatively new kid on the speed-control block, there are various other means to vary speed and control different motors. Speed reduction with small AC induction motors is often done with variable-voltage methods such as using inline capacitors, TRIACS (a bidirectional switch), or tapped motor windings, says Hauer. He cautions though, that motor efficiency is reduced significantly and the motor temperature rises. “This is why evaporator fans and small condenser fans are seldom speed controlled with voltage reduction,” he says.

Enlarge this picture Source: Food Service Technology Center

In terms of industrial and large, commercial walk-in coolers, many now use variable-speed motors with electronic drives. Large condenser fans are becoming equipped with continuously variable control instead of on/off operation and often use just one TRIAC-controlled lead-fan. “The challenge here lies in making the electronics withstand the elements. TRIAC motor control is not suitable if acoustic noise is of concern,” says Hauer.

For refrigeration products that employ 3-phase equipment, it may appear appealing to install variable-frequency drives (VFDs). Hauer cautions that careful evaluation is then necessary to prevent motor failures from VFD generated voltage spikes and common-mode currents arcing through the motor bearings. Because the VFD itself has some losses, electricity savings can be negated if the refrigeration load profile requires high fan speed.

Advanced ECM fans are more efficient than VFD equipment and they maintain high efficiency throughout the control range, cause no noise penalty, and can provide some refrigeration control functions directly within the motor package. Most importantly, ECM motors are matched to the electronics so that there are no voltage spike or bearing current problems.

According to Jenkins, the use of VFD motors usually incurs additional cost and is normally applied to higher output power motors (fractional and up) for larger fan blades or for compressor drives.  

This exploded view of an ebm-papst 1.5 HP EC fan motor with integrated electronics and fan blade.

One of the benefits of ECMs is the flexibility they offer, says Hauer. For instance, the motor speed does not depend on the AC line frequency so that 60 Hz equipment will perform equally in the 50 Hz world. “Besides, smaller fans running at higher than 2-pole synchronous speed provide a space-saving potential,” he says. “The more motor controllability and diagnostics are appreciated in an application, the easier it is to justify the investment in EC motors.”

In ebm-papst and other studies, the ECM motors offered direct savings in terms of energy efficiency (see Chart 1). In another study by GE ECM that compared motors, the ECM had a higher electrical efficiency (70 percent efficient) than PSC (49 percent efficient) or shaded-pole (32 percent efficient). Watt-for-watt, ECM can use up to a third as much energy when running at rated speed. ECM also maintains its efficiency across its speed range, whereas an induction motor’s efficiency plummets when its rated speed is altered, Neal says.

In addition to the direct benefits, Hauer adds that there are a number of indirect benefits such as less heat load on air-conditioned space when used with evaporator coils.

In evaporating unit applications, a high efficiency fan results in “cooler” motor operation, with lower heat released inside the refrigeration cycle as compared to traditional shaded-pole fans. In the past, most evaporator units featured fans driven by shaded-pole or permanent-split-capacitor fan motors. Efficiencies for ECM motors are generally four and five times the efficiency of a traditional shade pole motor, says Jenkins.

An exploded view of the GE ECM by Regal Beloit ICE 59. The EC motors works with VAC, PWM, and DSI inputs.

“The consequent lower demands of refrigeration capacities generate a combined energy saving effect, improved cooling quality and temperature stability inside the cooler, reduced moisture formation on the evaporator and consequently longer defrost intervals,” says Jenkins. “This immediate dollar saving on the final user’s energy bill allow an extremely short pay-back time (less than 6 months) on both new and retrofit installations.

Elco recently released its second generation of ECM products, the MCE-IP65 and MCE-IP66 Long Life (with ball-bearings) that can drive 8-in.and 10-in. fans and feature efficiencies of up to 70 percent.  These fans are available for 115 V and 230 V at 50/60 Hz power supply.

Neal adds that while for any given application, manufacturers choose the components to use based on size, input, and performance requirements, as well as the cost of adapting existing designs to fit a new motor, in the context of California’s ECM mandate,  equipment designers must determine how to take an advanced motor and slot it into an existing design that calls for a small, uncomplicated component.

That is why motor manufacturers are developing products that are “nearly identical in size and function to that of conventional evaporator-fan motors,” says Neal. While most motors are easy to drop in, Jenkins adds that sometimes the brackets need to be tweaked to better mount the motor. Jenkins says that Elco’s motor mounting design features a modular plastic shroud that is well established within the European commercial refrigeration appliance manufacturers and the ECM motor is meant as a perfect drop-in replacement.

Ebm-papst’s A3G800 axial fan works with its electronically commutated motors.

Another benefit of the more efficient motors is that the lower heat generation and improved airflow means the refrigeration system can be downgraded. “They are normally happy about it because they can save some money on the vent side,” says Jenkins.

ECM motors, which feature completely integrated electronics, can benefit designers that have to design products that have to work both with 50 Hz and 60 Hz markets. “They find that ECM motors are not affected from this frequency difference, while the traditional shaded-pole motors are affected,” says Jenkins. “The nominal speed of 50 Hz is 1,350 RPM, and 60 Hz is 1,550 RPM, which is a 15 percent to 20 percent difference in airflow between the two frequencies, so that changes the design. With an ECM motor there is no change between the two frequencies so they can use the same fan blade and everything.”

Neal adds that a motor’s capability to work with various inputs is an important feature when working with existing designs. The ICE 59, for instance, works with three motor control schemes — multiple line voltage inputs, pulse-width-modulation and direct serial interface. Neal says that multiple line voltage input is the easiest way to create multiple-speed equipment without high development costs. For a second discrete speed, a third wire can be added to the conventional two-wire voltage input. VAC control can help manufacturers update existing equipment to meet California Title 20 rules, because it makes ICE 59 a motor-for-motor match to conventional shaded-pole designs, says Neal.

The PWM works with existing variable-speed equipment, using the manufacturer’s plug harness to modify motor speed from 500 RPM to 1,800 RPM. Product developers gain access to the motor’s full range of operating speeds, but it comes at the cost of having to develop an external fan controller that can send the PWM signal to the motor.

Enlarge this picture Source: Food Service Technology Center

Digital serial interface gives designers access to the built-in intelligence of the ICE 59, including live command processing, real-time speed control, and BlaKBox Diagnostics, a data recorder built into the motor control board.

“Interchangeable controls are tremendously important for backwards compatibility with existing products, but it also allows designers to create gradual system redesigns without having to create an entirely new equipment platform, says Neal. “If a designer makes an incremental change to system components, the original ICE 59 motor can accept a different kind of control input or be adjusted to run at a more appropriate speed.”

The ability to replace traditional shaded-pole motors with more efficient ECM units was confirmed by researchers at the Food Service Technology Center (FSTC) in testing for Pacific Gas & Electric Co. The testers installed and monitored two GE ECM motors in a walk-in freezer. The motor utilized a permanent magnet, three-phase, brushless DC motor combined with a built-in electronic AC inverter that was used to drive it. The freezer evaporator unit originally came equipped with two shaded-pole 1/15 HP fan motors, but was retrofitted. The initial measurement of the original SP motor fans’ input power was 271 W with the two fans combined. Following the retrofit, the power was 88 watts for two fans combined. The average supply voltage throughout the two-week monitoring period was 207.4 V. Overall, the ECM equipped fans used 67 percent less energy.

The ability of EC motors to use less energy in applications, which typically consume a lot of energy, is not merely the wave of the future, but it is a technology whose time is already here. Whether driven by regulations or energy costs, manufacturers of commercial refrigeration equipment will continue to pursue more efficient technology even if that technology is initially more expensive.

For more information, email:
Ebm-papst: sales@us.ebmpapst.com
Elco Motors: sales@elcomotors.com
GE ECM by Regal Beloit: ecm.marketing@regalbeloit.com