An electronically commutated motor and control means therefor. The electronically commutated motor has no dead zone and no overlap despite an imperfect position detecting signal. The transition of the commutation is carried out in a differential manner. Any fluctuation in the operating temperature and/or deviation of the supply voltage does not disturb the commutation. The generating torque of the motor is easily controlled by a small power without using any additional power control means. A constant torque motor and a constant speed motor are illustrated.
An improved maintenance free fractional horsepower brushless direct current motor of the solid state switching circuit type wherein a rotational transducer secured to the motor shaft cooperates with each of the three detecting coils provided within a stator of the motor to excite each of the three stationary windings in order to revolve the motor into a predetermined direction.
12-step motor commutation is provided by a three-phase sinusoidal signal generator and related circuitry. Circuitry which compares the voltage outputs of two primary signals provides two additional switching points for every 360 electrical degrees. Three comparator circuits provide six additional switching points. Primary voltage outputs are weighted in the ratio of 2:1 prior to comparison.
A method of reducing torque ripple and noise for an brushless DC machine comprising: determining a control frequency for the electric machine, the control frequency indicative of an existing current command to and a rotational velocity of the electric machine; multiplying the control frequency by a selected multiple and forming a modulating signal responsive thereto; and formulating a modified command profile. The method also includes: correlating and synchronizing the modified command profile with the existing current command and a rotor position for the electric machine; and generating a modulated current command to the electric machine.
