Analysis: Use of brushless motors grows for factory floor and beyond
Thousand Oaks, CA — Brushless permanent magnet (PM) motors continue to evolve into high torque, high efficiency, smaller sized packages. They currently dominate electric motors in office automation (such as printers, disk drives, CDs, DVDs, and photocopiers), medical instruments (centrifuges, blood analysis, CAT scans, metering pumps), and a wide range of factory floor automation applications (including robots, semiconductor equipment, material handling, packaging machines, nut runners, machine tool drives). Now, they are beginning to move into lower-cost, high-volume automotive and appliance applications, albeit in selective cases.
Brushless PM motors — also known as brushless dc, brushless ac synchronous, and brushless servo motors, among others — have benefited from the discovery of rare earth magnets, best represented by samarium cobalt and neodymium-iron-boron types. Magnet manufacturers continue to improve incrementally the rare earth magnet’s magnetic energy levels, approaching 55 mega-gauss-oersteds. An Olympic weightlifter would find it difficult to pull such a magnet off the refrigerator.
Concurrent development of solid-state devices in the form of integrated circuits (ICs), power modules (inverters), microprocessors, and digital signal processors (DSPs) is providing the impetus for cost effective drives with electronic commutation approaching $10 in some high-volume-speed based applications. Integrating power and control functions equips the motion control user with the tools needed to construct a full motion control system. This continuous revolution in power and control electronics gives these devices the capability to expand into new applications.
The brushless PM motor is considered an excellent servo motor. Its high-torque and high-power efficiency allows for its use in smaller devices and machines. Although servo motors are used in precision position applications, in high performance incremental motion application, efficiency plays a direct role in terms of minimizing losses, thereby providing the motor with superior thermal performance. Lower eddy currents, hysteresis, and parasitic losses in the motor mean more thermal headroom and higher torque levels.
Today’s motor design engineer has superior design simulation tools available to take advantage of more customized brushless PM motors with improved performance. All motor types benefit from FEA (finite element analysis) and global simulation tools. The intrinsic performance advantage of the brushless PM motor and the latest integrated drives will promote new applications, particularly in power applications of 10 kW and lower.
For more on servo systems, see Product Research article on servo motors, p. 54, in the January 2008 Control Engineering North American edition, available online at www.controleng.com/archive
Where are you starting to apply brushless permanent magnet motors that you hadn’t previously? Have any questions or recommendations about the use or application of these motors?
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