Optimizing Motor Constant Km (Electric Motors)

10.13.4
The thousands of applications that use a BLDC motor make it impossible to determine a simple criteria in selecting the best BLDC motor for a given application. For motor designers, there is a single figure of merit that can determine if the motor design engineer has optimized the design in terms of magnetics and stator winding conditions. The figure of merit (motor constant Km), along with the motor’s dimensions does provide a relatively simple but effective method of evaluating a BLDC motor design. This also assumes that the proper magnet material has been selected, based on cost as well as dimensional requirements.

• Changing to high-energy magnets
• Increasing motor OD or AL
Usually the motor’s available input voltage and current levels will act as a limit to optimizing Km beyond a certain limit.The challenge for the motor design engineer is to maximize Km within specified electric inputs or friction and inertia requirements which will yield the best overall magnetic design.