A brushless motor with a microcomputer-based speed control system, but without a shaft-mounted position sensor, is described. The motor terminal voltages are used to obtain rotor position information. Speed control in the system is carried out through chopper control of the inverter itself, much as in chopper-fed DC motors. Various processes, including the speed control process, are controlled by developing the appropriate software. The limits of position sensing under a motor load are also described.

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