US 2012/0256580 A1Published application

System and method for fast start-up of an induction motor

AssigneeEaton Corporation

InventorsAnbo Yu, Lei Zhang, Kevin Lee

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Abstract

A system for controlling operation of a motor drive during fast start-up of an induction motor is disclosed. The system includes an AC motor drive having a PWM inverter and a control system to generate a command signal to cause the PWM inverter to control an output of the AC motor drive. The control system includes a start-up modulator that is selectively operable during start-up acceleration of the AC motor, the start-up modulator programmed to determine a motor current applied to the AC motor and a voltage of a DC bus, generate a first frequency offset that causes a frequency reference of the command signal to be decreased when the motor current is greater than a reference current threshold, and generate a second frequency offset that causes the frequency reference of the command signal to be increased when the DC bus voltage is greater than a reference voltage threshold.

Claims20

Dependent claims

A system to control operation of an AC motor, the system comprising:

an AC motor drive having an input connectable to an AC source and an output connectable to an input terminal of an AC motor, the AC motor drive comprising:
a rectifier connected to the input;
a pulse width modulation (PWM) inverter connected to the rectifier by way of a DC bus and having a plurality of switches therein to control current flow and terminal voltages in the AC motor;
and
a control system connected to the PWM inverter and being configured to generate a command signal to cause the PWM inverter to control an output of the AC motor drive corresponding to the input to the AC motor, the command signal including a frequency reference and a voltage reference;
wherein the control system includes a start-up modulator that is selectively operable during a start-up acceleration of the AC motor to a desired reference speed, the start-up modulator being programmed to:
determine each of a motor current applied to the AC motor and a voltage of the DC bus;
generate a first frequency offset that causes the frequency reference of the command signal to be decreased when the motor current is greater than a reference current threshold;
and
generate a second frequency offset that causes the frequency reference of the command signal to be increased when the DC bus voltage is greater than a reference voltage threshold.

7 more elements

A method for controlling operation of an AC motor during acceleration of the AC motor in a start-up mode of operation by way of a motor drive, the method comprising:

generating a command signal in a control system of the motor drive based on a desired speed of the AC motor, the command signal including a frequency reference and a voltage reference;
transmitting the command signal to a pulse width modulation (PWM) inverter of the motor drive to control an output of the PWM inverter, thereby controlling current flow and terminal voltages in the AC motor;
and
incrementally adjusting the command signal transmitted to the PWM inverter during the start-up mode of operation based on a motor current applied to the AC motor and a voltage an a DC bus of the motor drive, wherein incrementally adjusting the command signal comprises:
determining each of the motor current applied to the AC motor and the DC bus voltage;
comparing the motor current to a reference current threshold and the DC bus voltage to a reference voltage threshold, respectively;
decreasing the frequency reference in the command signal if the motor current is greater than the reference current threshold;
and
increasing the frequency reference in the command signal if the DC bus voltage is greater than the reference voltage threshold.

6 more elements

An AC motor drive to control transmission of voltage and current from an AC power source to an AC motor, the AC motor drive comprising:

an input and an output connectable to an AC source and to an input terminal of the AC motor, respectively;
a rectifier connected to the input;
a pulse width modulation (PWM) inverter connected to the rectifier by way of a DC bus and having a plurality of switches therein to control current flow and terminal voltages in the AC motor;
and
a control system connected to the PWM inverter and configured to:
determine each of a root mean square (RMS) current applied to the AC motor and a voltage of the DC bus;
compare the RMS current and the DC bus voltage to a reference current threshold and a reference voltage threshold, respectively;
determine a first frequency offset based on the comparison of the RMS current value to the reference current threshold;
determine a second frequency offset based on the comparison of the DC bus voltage to the reference voltage threshold;
combine the first frequency offset and the second frequency offset to determine a composite frequency offset;
and
generate a modified frequency reference in the command signal based on the composite frequency offset.

9 more elements

Dependencies are inferred from the claim text.