초록 ▼

Apparatus and method for high slip operation of an AC electric motor at substantially zero rotation and substantially zero torque in an AC electric motor drive system is disclosed. The electric motor produces a rotation in response to an outgoing signal, such as a drive current, of variable magnitud

Apparatus and method for high slip operation of an AC electric motor at substantially zero rotation and substantially zero torque in an AC electric motor drive system is disclosed. The electric motor produces a rotation in response to an outgoing signal, such as a drive current, of variable magnitude and frequency supplied by the drive system. An idle control signal is furnished when the drive system is in a substantially zero rotation and substantially zero torque state, where the frequency of the current is approximately zero. The idle control signal causes substantially simultaneously an adjustment of the magnitude of the current to a predetermined magnitude level and a rapid raising of the frequency of the current to a higher frequency value to produce per-unit slip s=(n1-n)/nb greater than 0.1, where n1 is the synchronous rotation of the stator field of the motor, n is the rotation of the rotor of the motor, and nb is the synchronous speed of the stator field at motor rated rpm. The adjustment in the magnitude and the rapid increase in the frequency of the current causes the motor to produce substantially zero rotation and substantially zero torque because the motor is operating in the high slip region of its torque-rotation curve. The apparatus and method of the present invention allows the motor to accelerate rapidly on command from the substantially zero rotation and substantially zero torque high slip mode.

대표청구항 ▼

A substantially zero rotation and substantially zero torque apparatus for an AC electric motor drive system having an AC electric motor producing a rotation in response to a drive current of variable magnitude and frequency comprising: (a) means for establishing a rotation reference signal proportio

A substantially zero rotation and substantially zero torque apparatus for an AC electric motor drive system having an AC electric motor producing a rotation in response to a drive current of variable magnitude and frequency comprising: (a) means for establishing a rotation reference signal proportional to a desired level of motor rotation; (b) means for generating an actual rotation signal proportional to the rotation of the motor; (c) means for generating a rotation difference signal as a function of any difference between said rotation reference signal and said actual rotation signal; (d) means for supplying a torque command signal in accordance with said rotation difference signal, and for producing a frequency control signal and a current control signal as functions of said torque command signal; (e) means for supplying drive current to the motor at a frequency controlled in response to said frequency control signal and at a magnitude varied in accordance with said current control signal; (f) means for furnishing an idle control signal when said torque command signal and at least two of said rotation reference signal, said actual rotation signal, and said rotation difference signal are less than respective predetermined values; and (g) first and second modifying means each responsive to said idle control signal for, respectively, changing the magnitude and rapidly raising the frequency of the drive current to cause the motor to produce a substantially zero rotation and substantially zero torque at high slip.