No-Load Investigations of Sub-Fractional Horsepower Permanent Magnet Motors

Accurately measuring the cogging torque, hysteresis torque, and iron losses of permanent magnet motors is a challenging task. This is especially true for sub-fractional horsepower variants used, e.g., in auxiliary drives for automotive fan and pump applications.

Their cogging torque and hysteresis torque peak values are often in the sub-milli-Newton meter range, causing conventional measuring methods and devices to fail as especially friction impedes the measurement significantly. Moreover, the iron losses of such motors are hard to determine and usually merely estimated in the literature.

Fortunately, a rheometer (universal micro testing machine MCR) can provide a remedy.

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