Appliance Design - January 2008 - (Page 32)

MOTORS An exploded view of the GE ECM by Regal Beloit ICE 59. The EC motors works with VAC, PWM, and DSI inputs. Ebm-papst’s A3G800 axial fan works with its electronically commutated motors. 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. 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 32 applianceDESIGN January 2008 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. “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. 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. 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Table of Contents Feed for the Digital Edition of Appliance Design - January 2008

Appliance Design - January 2008 Contents Editorial Shipments/Forecasts News Watch Makers of Commercial Refrigeration Equipment Turn to Variable-Speed Motors to Improve Energy Efficiency. New Motor Design and Control Scheme Makes Brushless Motors More Economically Feasible for a Wider Range of Applications. External Gas Molding, a Relatively New Technique, Solves Many of the Challenges Associated with the Injection Molding of Large Plastic Parts. Plastic Housings Offer Many Benefits: EMI Protection Isn't One of Them. But, New Materials and Techniques are Solving that Problem. Choosing the Optimal Strategy for Effective EMI Shielding Depends on Both Mechanical and Electrical Requirements Ethernet-Enabled Microcontroller Makes Networking Schemes Easier and More Cost Effective to Implement The Ever-Changing Array of Microcontroller Memory Options Makes it Imperative to Keep Abreast of What's Available to Determine the Optimal Choice for an Application. A Vast Range of Components and Finished Products will be Exhibited at the Country's Preeminent HVAC/R Show, AHR Expo, which is Scheduled for Jan. 22-24 in New York. Advertiser's Index Association Report: PRBA

Appliance Design - January 2008

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