CONSTANT SPEED ELECTRIC MOTOR

摘要

A constant speed brushless D.C. motor of the permanent magnet outside rotor type with an internal stator wired in quadrature having a pair of Hall effect switches one of each mounted in proximity to one of a pair of opposite stator wirings to sense the direction and phrase relationship of the field in the rotor, a coarse feedback loop sensing back electromotive force in said motor including first comparator for comparing the negative generated motor voltage and motor potential said Hall effect switches operating under the influence of said first comparator to control power to said motor and thereby control its speed, a fine speed control loop including a tachometer for generating electrical pulses in proportion to motor speed upon rotation of said rotor, counter means counting said pulses and a second comparator connected to said counter means for comparing the frequency of said electrical pulses having a given frequency and the electrical pulses representing a steady desired preset motor speed providing a balancing potential difference at said second comparator thereby achieving a frequency lock to lock in the motor speed. An electrical dynamic brake is disclosed.