Motor Controller

Selecting a Motor Controller for Electrical Drives

One reason is that the brushless motors often used in high-performance motion-control applications have quite a simple construction. Motor components, which include the motor controller, can be thought of as building blocks consisting of laminations and magnets. This allows motion-control suppliers to inventory a large array of basic building blocks used in developing motors for special requirements. All other components such as the motor controller, copper wire, bearings, motor housing parts, shaft and rotors, shaft encoders and readers are either generally available commodities or can be modified with short lead times.

In terms of motor controller performance, optimization generally considers factors such as the actual peak and rms torque requirements or whether a dc supply voltage is available. The need for an enclosed or open frame and special interface specifications can also be built into custom specifications.

For example, consider simple velocity control over a 500 to 5,000-rpm speed range. A standard motor controller will require either a resolver or encoder to provide the feedback signal for velocity. But such feedback components might be an overspecification for this speed range. Instead, Hall-effect commutation sensors on the motor itself might provide velocity sensing that would work as well.

The motor controller interface often can be optimized in other ways. The motor controller can be optimized by designing the BEMF constant of the motor and the dc bus voltage of the motor controller to yield a maximum speed that is less than 10 to 15% above the highest operating speed. This ensures that certain failure modes do not produce high runaway speeds.

A motor controller can also be optimized through modification to the direct-drive application where speeds are low (0 to 500 rpm) and torques high. Here, custom motor / motor controller combinations can be configured to get more power from smaller motors, use less energy for a given task, obtain faster acceleration and deceleration rates to improve throughput, reach higher or more precise operating speeds, meet precise positioning criteria, improve heat dissipation for cooling, and reduce maintenance or lengthen operating life.

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Motor Controller: Motor Controller Information

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