Zero rotation and zero torque detector and method for an AC electric motor drive

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, said apparatus comprising:

• (a) means for establishing a torque reference signal proportional to a desired level of torque;
• (b) means for generating an actual rotation signal proportional to said rotation;
• (c) means for generating a torque command signal as a function of said torque reference signal, and for producing a frequency control signal and a current control signal as functions of said torque command signal;
• (d) means for supplying to said motor said drive current at a frequency controlled in response to said frequency control signal and at a magnitude varied in accordance with said current control signal;
• and
• (e) means for furnishing an idle control signal when said actual rotation signal and said torque reference signal are less than respective predetermined values, whereby said idle control signal indicates that the drive system is in a substantially zero rotation and substantially zero torque state and is effective to control an operation parameter of said drive system.

A method of furnishing an idle control signal in an AC electric motor drive system having an AC electric motor producing a rotation in response to an outgoing signal of variable magnitude and frequency comprising the steps of:

• (a) establishing a rotation reference signal proprotional to a desired level of rotation;
• (b) generating an actual rotation signal proportional to said rotation;
• (c) generating a rotation difference signal representative of any difference between said rotation reference signal and said actual rotation signal;
• (d) supplying a torque command signal as a function of said rotation difference signal;
• (e) producing a frequency control signal and a current control signal as functions of said torque command signal;
• (f) supplying to said motor said outgoing signal at a frequency controlled in response to said frequency control signal and at a magnitude varied in accordance with said current control signal;
• and
• (g) furnishing an idle control signal when said torque command signal and at last two of said rotation reference signal, said actual rotation signal, and said rotation difference signal are less than respective predetermined values, whereby said idle control signal indicates that the drive system is in a substantially zero rotation and substantially zero torque state and is effective to control an operation parameter of said drive system.

A method of furnishing an idle control signal in 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 the steps of:

• (a) establishing a rotation reference signal proportional to a desired value of rotation;
• (b) generating an actual rotation signal proportional to said frequency of said drive current;
• (c) generating a rotation difference signal representative of any difference between said rotation reference signal and said actual rotation signal;
• (d) supplying a torque command signal as a function of said rotation difference signal;
• (e) producing a frequency control signal and a current control signal as functions of said torque command signal;
• (f) providing from a variable DC current source a DC output current having a magnitude varied in response to said current control signal;
• (g) supplying from an inverter said drive current to said motor at a frequency controlled as a function of said frequency control signal;
• (h) providing link circuit means including an inductor for connecting said DC current source to said inverter via a link circuit including an inductor;
• and
• (i) generating 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, whereby said idle control signal indicates that the system is in the substantially zero rotation and substantially zero torque mode and is effective to control an operation parameter of said drive system.

A method of furnishing an idle control signal in an AC electric motor drive system having an AC electric motor producing a rotation in response to an outgoing signal of variable magnitude and frequency comprising the steps of:

• (a) establishing a torque reference signal proportional to a desired level of torque;
• (b) generating an actual rotation signal proportional to said rotation;
• (c) generating a torque command signal as a function of said torque reference signal;
• (d) producing a frequency control signal and a current control signal as functions of said torque command signal;
• (e) supplying to said motor said outgoing signal at a frequency controlled in response to said frequency control signal and at a magnitude varied in accordance with said current control signal;
• and
• (f) furnishing an idle control signal when said actual rotation signal and said torque reference signal are less than respective predetermined values, whereby said idle control signal indicates that the drive system is in a substantially zero rotation and substantially zero torque state and is effective to control an operation parameter of said drive system.

A method of furnishing an idle control signal in 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 the steps of:

• (a) establishing a torque reference signal proportional to a desired value of torque;
• (b) generating an actual rotation signal proportional to said rotation;
• (c) generating a torque command signal as a function of said torque reference signal;
• (d) producing a frequency control signal and a current control signal as functions of said torque command signal;
• (e) providing from a variable DC source a DC output current having a magnitude varied in response to said current control signal;
• (f) supplying from an inverter said drive current to said motor at a frequency controlled as a function of said frequency control signal;
• (g) connecting using a link circuit including an inductor, said DC current source to said inverter;
• and
• (h) generating an idle control signal when said actual rotation signal and said torque reference signal are less than respective predetermined values, whereby said idle control signal indicates that the system is in the substantially zero rotation and substantially zero torque mode and is effective to control an operation parameter of said drive system.