issue: June 2007 APPLIANCE Magazine
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With a wide range of motoring and loading capabilities, a new motor-testing system can reportedly perform the testing typically done with several different systems — all with a single capital investment.
The DynoLab EM electric motor test system from Sakor Technologies Inc. is said to help appliance manufacturers test a variety of motors, including dc, brushless dc, ac induction, and permanent ac magnet motors. In fact, according to the Okemos, Michigan, U.S.–based company, when utilizing its AccuDyne ac motoring dynamometers, the
system can cater to almost any testing need.
“Appliance engineers can use the [motor-testing] capability to qualify manufacturers, specific motor models, or drivetrain components for use in their product,” notes Randy Beattie, president of Sakor. “The fact that the AccuDyne is a motoring dynamometer, however, makes it much more generally useful. In the testing laboratory, it can be used in place of the motor to drive transmissions, drivelines, or the entire appliance. While doing this, it can directly measure torque, speed, and the power requirements necessary to properly drive that appliance. From these data, specifications for the proper motor required for the device can be developed with actual measured data, rather than estimated (calculated) values.”
In a dishwasher, for example, the appliance engineer can use the system to completely characterize the operation of the dishwasher motor’s performance in all normal and unusual circumstances, including a locked rotor. “The same system can be used to perform unattended 24/7 durability testing over many thousands of hours, as required,”
Beattie explains. “The system is also capable of accepting data logged from actual (properly instrumented) units in the field and ‘playing back’ these data on the test bench. In this way, actual in-use simulation can be performed on the motor.”
In fact, Beattie says that when fitted with the proper fixtures, the system can also be used to gather performance requirement data by actually replacing the drive motor in the dishwasher and taking direct readings of torque, speed, and power required to operate the dishwasher. “These data can then be used to determine the proper motor to be used in the product,” he explains.
Designed to meet EPAct, NEMA, ISO, IEEE (112 and 115), and other international standards, the test system itself is said to be extremely power efficient. By utilizing the dynamometers and a unique regenerative method of electrical loading, Beattie says the test system is highly efficient at recirculating absorbed power within the system, resulting in a solution that can test even the largest electric motors while drawing only minimal power from the electrical grid, and generating almost no waste heat.
“As an ac dynamometer, it is inherently regenerative,” Beattie explains. “This means that the power that is absorbed is regenerated back to the ac mains rather than being used to generate heat. In this way, it requires virtually no cooling, is extremely power efficient, and, therefore, has a very low cost of operation.”
He adds that the phrase “regenerative method of electrical loading” refers to the fact that the test system will not only provide loading and motoring with the AccuDyne, but will also provide electrical power to, or loading of, the customer’s device as well. “In this configuration, any power that is used to drive the system via the dynamometer customer’s device is absorbed by the other device and placed back to the internal power bus (less electrical and mechanical losses),” Beattie says. “This absorbed energy is then recirculated back in to power the system. This configuration reduces the power drawn from the ac mains to that of the electrical and mechanical losses in the system, which are typically a very small percentage of the total system power.”
Beyond the energy efficiency and operating-cost savings, Beattie says that this feature provides very precise, automated control. “Since the system is in control of both the drive and loading components (e.g., the dynamometer and customer component), it can perform completely automated closed-loop testing,” he explains. “This, in turn, helps to guarantee precise and repeatable results.”