Brushless DC motor operation at
high speeds as affected by the core losses
The brushless dc (bldc) motor is now being used in a number of high performance applications where motor speeds of 10,000 to 30,000 rpm are achieved. The impact of iron losses cannot be ignored and must be included in any design procedure for these high speed applications. This paper will compare the various design tradeoffs of the internal motor losses in small bldc motors, specifically a 2.0" O.D. and a 3.0" O.D. bldc motor, when operating at high speeds. These losses include eddy current, hysteresis and copper losses. The results will be presented and a number of computer simulation solutions will be shown. These will be used in optimizing different performance parameters. Some of these results will be matched to various applications in the US market. The impact of the motor's thermal performance will limit the actual dissipated power that the brushless dc motor can achieve. A series of thermal resistance targets will be established which will be used as practical limits to the motor's ability (or inability) to dissipate heat.
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