Method and apparatus for adjustable voltage/adjustable frequency inverter control
AssigneeRockwell Automation Technologies, Inc.
InventorsDavid Leggate, Gary Leonard Skibinski, Gary R. Woltersdorf
Life of this patent
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Abstract
An apparatus and method for controlling an inverter, the apparatus including an adjustable frequency controller receiving a reference frequency value and generating a command frequency value as a function thereof, an adjustable voltage controller receiving a reference voltage value and generating a command voltage value as a function thereof and independent of the command frequency and a modulator receiving the command frequency value and the command voltage value and generating pulse width modulated (PWM) inverter control signals as a function thereof.
Claims32
An apparatus for controlling an inverter to provide exciting currents to stator windings of an induction motor that includes a rotor where the rotor is not physically connected to an external excitation source, the apparatus comprising:
- an adjustable frequency controller receiving a reference frequency value and generating a command frequency value as a function thereof;
- an adjustable voltage controller receiving a reference voltage value and generating a command voltage value as a function thereof and independent of the command frequency;
- and
- a modulator receiving the command frequency value and the command voltage value and generating pulse width modulated (PWM) inverter control signals as a function thereof;
- wherein the inverter control signals are provided to the inverter to control the inverter.
The apparatus of claim I wherein the adjustable frequency controller also receives at least one of a maximum frequency value and a minimum frequency value and, wherein, the step of generating a command frequency includes generating the command frequency value as a function of the reference frequency and the at least one of the maximum frequency value and the minimum frequency value.
A method for controlling an inverter to provide exciting currents to stator windings of an induction motor that includes a rotor where the rotor is not physically connected to an external excitation source, the method comprising the steps of providing a controller that is programmed to perform the steps of:
- receiving a reference frequency value;
- using the reference frequency value to generate a command frequency value;
- receiving a reference voltage value that is independent of the reference frequency value;
- using the reference voltage value to generate a command voltage value independent of the reference frequency value and the command frequency value;
- using the command frequency value and the command voltage value to generate pulse width modulated (PWM) signals for controlling the inverter;
- and
- using the PWM signals to control the inverter.
An apparatus for controlling an inverter to provide exciting currents to stator windings of an induction motor that includes a rotor where the rotor is not physically connected to an external excitation source, the apparatus comprising:
- an interface for specifying a reference frequency value and a reference voltage value that is independent of the reference frequency value, the interface also for specifying at least a subset of additional information including frequency acceleration and deceleration reference values, voltage acceleration and deceleration reference values, maximum and minimum frequency values and maximum and minimum voltage values;
- an adjustable frequency controller receiving the reference frequency value and, where the subset of additional information includes at least some frequency related information, receiving the at least some frequency related information, and generating a command frequency value as a function thereof;
- an adjustable voltage controller receiving the reference voltage value and, where the subset of additional information includes at least some voltage related information, receiving the at least some voltage related information, and generating a command voltage value as a function thereof and independent of the command frequency;
- and
- a modulator receiving the command frequency value and the command voltage value and generating pulse width modulated (PWM) inverter control signals as a function thereof;
- wherein the inverter control signals are provided to the inverter to control the inverter.
A method for controlling an inverter to provide exciting currents to stator windings of an induction motor that includes a rotor where the rotor is not physically connected to an external excitation source, the method comprising the steps of providing a controller that is programmed to perform the steps of:
- during a commissioning procedure:
- receiving a reference voltage value;
- receiving a reference frequency value that varies between a maximum frequency value and a minimum frequency value;
- using the reference voltage value and the reference frequency value to generate PWM inverter control signals;
- using the PWM inverter control signals to drive the inverter;
- sensing inverter output current;
- and
- identifying the reference frequency value at which the inverter output current is maximized as a resonant frequency value;
- and
- after the commissioning procedure:
- using the reference voltage value and the resonant frequency value to generate PWM inverter control signals;
- and
- using the PWM control signals to drive the inverter.
Dependencies are inferred from the claim text.