US 5,032,771 AGranted

Slip control based on sensing voltage fed to an induction motor

AssigneeAllen-Bradley Company, Inc.

InventorsRussel J. Kerkman, Timothy M. Rowan

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Abstract

An electronic motor drive for vector control of an induction motor controls slip and operating frequency in response to changes in stator voltage. The drive includes a torque control loop, a flux control loop and a frequency control loop which includes slip control in response to a voltage difference. In the constant horsepower range, above base speed, slip is controlled in response to an error between a d-axis reference voltage that is sampled at base speed and a d-axis feedback voltage that is sensed when the motor is operating above base speeed. Flux-weakening is provided in response to an error between a q-axis reference voltage that is sensed when the motor is operating at base speed and a q-axis feedback voltage that is sensed when the motor is operating above speed.

Claims9

Dependent claims

A method for controlling slip in an induction motor having a stator and rotor, the method comprising:

controlling stator voltage in response to a difference between commanded stator current and actual stator current, and in response to a stator operating frequency command;
determining a rotor frequency that is responsive to the rotational speed of the rotor;
determining the stator operating frequency command from the rotor frequency and a slip frequency command;
generating a stator voltage command in response to a preset parameter;
determining voltage feedback representative of actual stator voltage;
determining a voltage error as a difference between the stator voltage command and the voltage feedback representative of actual stator voltage;
applying a control function to the voltage error to generate a slip multiplier for torque-producing current;
multiplying the slip multiplier by a command for torque-producing current to control the slip frequency command;
changing the slip multiplier in response to the voltage error to control the slip frequency command;
and
algebraically summing the slip frequency command and the rotor frequency to control the stator operating frequency command.

8 more elements

A motor drive for controlling the slip of an induction motor without initial adjustment of the drive for the effects of motor parameters, the motor drive being of the type adapted for electrical connection to means coupled to the rotor to sense the frequency of the rotor, the motor drive comprising:

a voltage inverter for generating voltages to be applied to the stator of an induction motor;
means for controlling the voltage inverter with a stator operating frequency command and with stator current commands, and in response to feedback representative of actual stator current;
means for generating a stator voltage command in response to a user input;
means for determining voltage feedback representative of actual stator voltage;
and
means for determining a voltage error as a difference between the stator voltage command and the voltage feedback representative of actual stator voltage;
and
means for applying a control function to the voltage error to generate a slip multiplier for torque-producing current;
means for multiplying the slip multiplier by a command for torque-producing to control the slip frequency command;
means for changing the slip multiplier in response to the voltage error to control the slip frequency command;
and
means for algebraically summing the slip frequency command and the rotor frequency to control the stator operating frequency command.

9 more elements

Dependencies are inferred from the claim text.