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issue: October 2005 APPLIANCE Magazine Part 2: Motors & Air-Moving Devices

Motors and Air - Moving Devices
Driving Motor Design


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by Jill Russell, Associate Editor

The demand to balance reliability, features and cost is driving appliance motor manufacturers to approach the design phase from a more fine-tuned perspective.

Developed by Eberle Equipment & Processes, a division of Brazil’s Mundial S.A., the Syllent pump features a motor and pump in a single package. For use in whirlpool baths and spas, the design involves an electric motor and pump, without a cooling fan, mechanical shaft seal, or motor bearings. “By creating the pump in a composite of thermal plastics and integrating the motor’s internal windings within the housing, making it electrically isolated, water is able to flow right though the middle of the motor,” explains Dave Hall, a sales engineer for the company. According to Eberle, the motor-pump is manufactured with injection molding equipment and is sealed after the electrical component has been placed. The company says that because water is able to flow through the motor, the unit is naturally cooled and the heat transferred to the water is flowed back in the whirlpool bath. “The integration of the pump and motor for utilization of heat energy is something that we think is important. Otherwise, it’s wasted energy,” Hall says.

Industry knows that in order to bring a successful product to market, the supplier and OEM must work together closely. At the risk of sounding cliché, the idea of establishing a relationship at the beginning of the design phase still holds true, especially when it concerns the “heart” of the appliance—it’s motor. Still, not everyone addresses motor needs in the most efficient way in the design process.

“You would be amazed how often a company has already designed a product and then comes to us as a second source,” Michael Rogen, vice president, Electronics, Sales and Marketing for Maxon Precision Motors (Burlingame, California, U.S.), tells APPLIANCE. “Being there first from a design point-of-view makes it easier because you are not limited to what somebody else is doing.

Besides being the second source on a new design project, motor suppliers are finding that appliance makers don’t always have a firm handle on the products specifications, making the entire process more complicated than it should be. There are steps that suppliers can take to help alleviate the frequency of the problem.

In order to eliminate becoming the second source in appliance design, and also in response to increased competition and prices, motor suppliers are becoming more aggressive in the way they do business, from start to finish.

The Carrier Infinity Series of gas furnaces (pictured) and air-conditioners feature an electronically controlled motor that communicates with the system compressor during operation. According to the company, the system monitors the outside temperature and humidity conditions along with the indoor air temperatures and adjusts the motor to operate in order to heat or cool accordingly.

Establishing Ground

The notion of a collaborative relationship between OEM and supplier is becoming commonplace. In the past, OEMs would typically complete the majority of design work before requesting sample blowers or propeller fans for those applications. Consequently, product performance would suffer because of various system effects that were not accounted for in the design process, explains Michael Brendel, vice president of Engineering and Marketing for Lau Industries (Dayton, Ohio, U.S.). More OEMs are beginning to realize that more effective solutions are available if we work together throughout the entire design process.

In response to the more cooperative design process, motor suppliers are finding that appliance producers are asking that they provide a more complete or “system” package with their motors.
Lau Industries refers to these as “motorized” packages, which include blowers, propeller fans, motors, drives, brackets, and other components that are supplied as a subassembly before the final assembly of the product. “OEMs are beginning to recognize the efficiencies and cost savings gained in buying the complete, assembled motorized air-moving package,” Brendel says. “This plug-and-play approach frees up floor space for the OEM and helps streamline supplier logistics.

A.O. Smith, a motor supplier based in Tipp City, Ohio, U.S., agrees that more OEMs are looking for subassemblies for motors and blowers rather than individual components. “They have come to us in the past for a motor, and now it’s motors, mounting brackets, wiring harnesses, and so on,” Mark Olson, A.O. Smith global market manager for Ventilation and Refrigeration, tells APPLIANCE. “We are trying to become more of a solution provider.”

One of the ways the supplier is achieving this is by working with customers on a case-by-case basis for new projects. Olson says that when working on a new project, the appliance maker will have a list of objectives and products they would like the supplier to provide. Instead of focusing on only the motor or blower, it works to provide multiple items on the list. “The main point is to show them we can do that and get away from the notion that ‘they didn’t invent it, they don’t do it’ mentality,” Olson says.

This has been achieved with A.O. Smith’s CoolBlue Solutions™, a line of high-efficiency motors, electronics and design ideas developed to help OEMs achieve the latest Season Energy Efficiency Rating (SEER) 13 standard. With the new line, the supplier says it can provide a solution that includes an evaporator, condenser and compressor motors that are controlled by a single, integrated set of electronics.

The line includes the A.O. Smith ECM motor, which the supplier says is designed to deliver constant cfm and features full programmability; the new Comfort Select™ motor, a brushless DC motor with high-speed electronic controls that features five speeds; an IPM compressor motor, featuring internal permanent magnets; and enhanced air-flow systems for high-efficiency furnaces, which are pre-packaged air-moving units that feature electronically controlled brushless DC motors integrated into the blower.

Additionally, A.O. Smith recently signed a technology licensing agreement with PaxFan, a research and development company specializing in air-moving technologies, that allows the motor supplier to optimize both its fan and motor product offering specifically for appliance applications. Under the PaxFan agreement, A.O. Smith says it has seen a 25-percent energy savings to date simply by matching the fan blade and motor combination for the application.

Besides offering “packaged” solutions, other suppliers are taking different approaches to initiate a close supplier-OEM relationship. One such supplier is Johnson Electric.

Headquartered in Hong Kong, with offices in Europe and in North and South America, Johnson Electric recently opened its Value Innovation Program (VIP) Center in China. The center allows engineers and appliance producers to create, model and test new product ideas. “The VIP center is intended to encourage more customers to come into a confidential environment, where they can discuss what they would like to do collaboratively and develop strategic products without fear that their intellectual property will pass to others,” Richard Baines, an engineer for Johnson Electric, says. “The idea is to create value and innovation.

The supplier also recently opened an engineering and production center in Moncalieri, Italy. Johnson Electric says the center focuses on brushless DC motors and electronic controls and is equipped with CAD systems, EMI (electromagnetic interference) chambers, acoustic chambers, and reliability testing labs.

Integrating electronic control into its motor designs, Maxon Precision Motors recently introduced its EC-powermax 30-mm brushless DC motor. The company designed the motor so that the coils are outside the rotor, which it says allows for good heat dissipation and high overload capability. The motor features a stainless steel housing and a maximum speed of 22,000 rpm. Designed for use in robotic and automated applications, the motor is available in different windings to accommodate desired speed and available voltage.

Efficient Services

As new energy efficiency guidelines approach, the relationship between supplier and OEM has become a key component in ensuring products meet the mandated requirements. To help appliance producers introduce products by the January 2006 deadline, motor suppliers are providing testing and qualification services in-house as a value-added service.

Bison Gear & Engineering, a motor supplier located in St. Charles, Illinois, U.S., was recently awarded a grant worth U.S. $100,000 by the National Science Foundation to fund research on higher efficiency electric motors. Bison says the research will aim to increase electric motor efficiency to 80 percent compared to the current average of 60 percent efficiency.

In addition, the research will help Bison develop a new, more efficient electric motor. “The motor under development will run 33 percent more efficiently,” Matt Hanson, vice president of Sales and Marketing told APPLIANCE. “The design occupies 50 percent less space and will cost less to manufacture than conventional motors.” According to Bison, the research will take place in its Design Studio located at the company’s headquarters and will start by focusing on the motor’s control algorithms.

As control algorithms become more advanced, the use of electronic controls has helped to increase the efficiency of motor and blower products. ebm-papst (Farmington, Connecticut, U.S.) recently introduced its Model RG175/2000-3633 blower designed for high-efficiency, condensing gas-fired boilers rated up to 500 BTU per hour. Powered by a brushless DC motor, which also features a vibration isolation system, ebm-papst says the blower was designed to fill a performance gap in the company’s line of premix-ready gas blowers. It says the blower is 100-percent speed controllable and compatible with Honeywell and Dungs gas valve assemblies, which deliver a measured air-to-gas mixture to the blower on demand.

Also using integrated sensors is Maxon, which recently introduced a new line of pancake motors that are said to be extremely efficient and reliable while offering a compact package. The motor is 90 mm in diameter and 29.1 mm in height and offers 90 W of output power. Maxon says that uniquely shaped motor has been a winning solution for several customers. “Our flat motors are often used in blower applications, where the main advantage of the brushless motor is the reliability that comes from having no brushes to wear out,” he says. “The flat motor shape opens a lot of doors for us. Quite often, you can’t fit a traditional motor in a certain space.” With a maximum speed of 5,000 rpm and an ambient temperature rating of -40°C to 100°C, Rogen says the motors are designed for use in automation and packaging equipment, robotics and pumps.

Reducing Noise, Increasing Reliability

The use of brushless DC motors helps keep products both quiet and reliable. Johnson Electric recently introduced a new end cap for miniature motors that is said to provide further noise suppression and thermal protection. Taking into consideration the fact that the closer the suppression circuit is to the source of the noise, the more effective it is, Johnson Electric designed an end cap to mount the suppression components inside the motor. The plastic end cap features cavities inside to place and hold the components. Brass parts placed inside the cavities allow the circuit to complete as the motors choke cable and capacitor are positioned.

In addition, the end cap features a positive temperature coefficient thermistor (PTC), which shuts the motor down if it reaches a temperature threshold to help eliminate the possibility of complete motor failure. According to Johnson Electric, the addition of the PTC prevents misuse of the application from causing damage to the appliance by switching off any large and damaging overload currents before failure occurs.

In order to achieve the internal design, Johnson Electric reconfigured the end cap and its relation to the motor. A typical suppression device works as the PTC is connected to a negative terminal through a capacitor. Next to the positive terminal is a choke that is connected to the brush, which rests on the commutator and is connected to the motor windings. The negative terminal is next to the PTC, which leads to another brush. However, as the supplier wished to place all the components inside the cap, the design was changed so that each of the components could be placed in a pocket, or cavity, in the end cap. In the new design, each component is placed in a pocket and connected to the complete circuit via a spring contact and pinched contact with the spring brass blades. Each motor terminal is a female-type and is located around the terminal posts. This protects the motor from damage if the male terminal is connected with too much force, Baines explains.

The idea behind this particular concept is that it protects the suppression elements by putting them inside the motor, instead of placing them outside,
Baines tells APPLIANCE. I think OEMs are looking for components that are almost impossible to damage when fitting them into their appliances.

Besides the actual motor, many noise considerations are related to fans. ebm-papst recently designed a mixed flow fan to help reduce noise levels in its product line that takes into consideration the blades of the fan impeller and the centrifugal acceleration of the device.

According to the supplier, the design overcomes higher back pressures without the need for major design modifications. The mixed flow design features a conical rotor hub with a small intake diameter, which increases toward the pressure side of the unit. ebm-papst says this creates a higher circumferential speed of the blade tips at the air exhaust, which, in turn, creates a higher centrifugal acceleration of the air. Because the impeller form is conical, the vortex can be minimized, allowing the fan to operate at low noise levels at high speeds.

Another supplier developing motors to decrease noise and increase product reliability is the DC Micro Motor Division of Sanyo (Bensenville, Illinois, U.S.). The motor supplier has engineered a DLP rear-projection TV color wheel motor containing ceramic air bearings. Sanyo says the ceramic material helps to reduce noise in TVs and projectors, as they do not produce any rolling or sliding resistance while in operation.

According to Shane Snipe, manager and mechanical engineer for Sanyo, the sleeve and shaft of ceramic air bearings contain a 3- to 5-micron gap between them. At the bottom of the shaft, magnets repel each other, and once the motor starts spinning, static air pressure is created in the gap. This allows the motor to operate without having any contact. Available in a 20 mm size, the sensorless motor is said to be extremely reliable, as the motor will operate as long as the bearings are in good condition. “It would last as long as it would take the air to wear out the ceramic,” explains Snipe. “Ceramic is very hard and the frictional wear of air is minimal, so basically it would last forever.

Related to this type of technology is the idea of fluid-bearing motors. Permawick Corporation (Birmingham, Michigan, U.S.), a supplier specializing in fluid-filled bearings and injection equipment, says this technology eliminates the need for manual maintenance of a motor because self-maintenance occurs inside the motor. Specializing in oil-filled sleeve bearings and lubricants, Permawick recently introduced a new line of low temperature synthetic oils for freezer motors.

Customers want smaller, less expensive motors to do more work and one of the consequences is elevated operating temperatures in the bearing,” says John Lane, president of Permawick. In response, the supplier developed a line of bearing lubrication oils using hydrocracked base oils that meet the need of higher bearing temperatures without being a synthetic oil. In addition, it has introduced a line of reservoir gels that have been used in electric household appliances such as juicers, blenders and mixers.

Lang says that gels are beneficial because they supplement existing oil and do not require a reservoir in the motor as oil does. “In larger bearing designs, there is enough real estate to accommodate wick material and an oil recirculation system. Smaller motors often lack this reservoir,” says Lang. “The advantage of gel is that it can be deposited on the surface around the bearing to offer a longer motor life.

Testing Techniques

Besides reducing motor noise, suppliers are also working to provide reliable motor products through quality testing. Heating, ventilation and air-conditioning (HVAC) manufacturer Carrier, headquartered in Farmington, Connecticut, U.S., said testing of the motor before and after installation is an important step in the production process.

We closely monitor our motor suppliers in our manufacturing facilities on a regular basis, evaluating products in assembly line tests. Tim Perry, manager of heating product marketing for the company, says Carrier strives for zero defects and that, in order to meet the demand, its motor suppliers conduct extensive testing to ensure quality. We 100-percent test run all of our products before they are shipped, he tells APPLIANCE. We also install the motor in the furnace and then run it in a quiet, enclosed chamber so operators can hear unusual or unacceptable noise.

One motor supplier conducting extensive testing on the assembly line is AEA, a part of the Italy-based Loccioni Group. The company has incorporated automated systems to conduct on-line inspections of its finished products. Dr. Cristina Cristalli, AEA R&D manager, says that in order to detect mechanical defects, the supplier studied noise and vibration measurements. Used to test washing machine motors and refrigerator compressors, computer-aided tests are now monitored for vibrations and noise levels to indicate motor defects.

According to Cristalli, all of the test systems are automatic and use a laser vibrometer to conduct the tests without physically touching the motor. “This allows us to measure vibration, for example, directly on the bearing housing or in positions where it is difficult to put an accelerometer, she explains.

In addition to testing for noise and vibration as defect indicators, other suppliers are choosing to focus on the motor temperature to signal possible malfunction. ACC, a Pordenone, Italy-based maker of motor compressors, says that some appliance makers consider the shell temperature as sufficient indication of the internal temperature, which can lead to errors. Instead, ACC says monitoring the coil winding temperature can help reduce problems and is designing motors according to the temperature norm of 130°C safe operating temperature for Class B compressors. To make sure the internal temperature is correctly monitored, ACC reads the winding temperature by measuring the motor winding resistance and has not exceeded the 130°C limit under the new tests.

Extensive testing, though, isnt the only thing that ensures a suppliers solution is successful. True success comes from knowing and meeting customer wants and needs and more motor suppliers are taking final application testing into their own hands literally.

GEs Motor Division says it helps to ensure success by having the appliance product in its own labs to assist with both design and testing. Youve got to know the applications to know the right questions to ask customers, says Robert Hollenbeck, an application systems expert for GEs Motor Division. We have a lot of appliances in our labs and we figure out how we would like to design the appliances in addition to what the customer wants. We can present options and go in the directions the customer wants.

 

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