Speed control of variable-speed multiple-phase motors
AssigneeEmerson Electric Co.
InventorsPing Shan, Cai Bing Zhang
Life of this patent
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Abstract
Exemplary embodiments or implementations are disclosed of methods, apparatus, and systems for operating motors in variable speed situations. In an exemplary implementation, a method of controlling a variable-speed motor includes defining a control duration as a predetermined number of cycles of a multiple-phase power supply. Each speed in a range of speeds is defined by a corresponding number of the cycles of the control duration. Power is provided to the motor from the power supply at a selected one of the speeds, by enabling input from the power supply for the number of the cycles of the control duration corresponding to the selected speed.
Claims20
A method of controlling a variable-speed motor, the method comprising:
- defining a control duration based on a predetermined number of cycles of an alternating current (AC) line frequency;
- defining each speed in a range of speeds by a corresponding fraction of the control duration;
- a controller providing a driver signal to an interface circuit for each of one or more phases of an AC power supply, to enable line voltage input to a variable-speed motor at the AC line frequency from the one or more phases for the fraction of the control duration corresponding to a selected one of the speeds;
- and
- each interface circuit detecting zero-crossing points of the line voltage independently of the controller and switching the line voltage input from the corresponding phase between “on” and “off” states at detected zero-crossing points of the line voltage input, such that an “on” time of each interface circuit of the one or more interface circuit corresponds to the fraction of the control duration corresponding to the selected one of the speeds, wherein the controller provides the driver signal to the interface circuit for each of the one or more phases of the AC power supply independently of the detecting of zero-crossing points of the line voltage by each interface circuit.
A method of controlling a variable-speed motor, the method comprising:
- a controller providing a driver signal to an interface circuit for a time period equal to a fraction of a number of AC line voltage cycles by which a full-speed driver signal to the motor is defined, the fraction corresponding to a selected motor speed;
- and
- the driver signal enabling the interface circuit to switch a line voltage input to the motor on or off upon detection of zero-crossing of the line voltage input by a zero-crossing circuit of the interface circuit, the interface circuit being enabled to switch on the line voltage input to the motor, at the line voltage frequency for the time period equal to the fraction corresponding to the selected motor speed;
- the driver signal to the interface circuit being provided by the controller independent of the detection of zero-crossing of the line voltage input.
A system for controlling a variable-speed motor, the system comprising:
- a controller configured to provide a driver signal configured in accordance with an AC line frequency;
- and
- one or more interface circuits each configured to deliver a corresponding one of one or more AC line voltage inputs to a load, each interface circuit having a corresponding zero-crossing circuit configured to detect zero crossing in the corresponding line voltage input;
- each interface circuit configured to:
- receive the driver signal from the controller;
- and
- based on the driver signal and the AC line frequency, enable or disable, collectively with the other one or more interface circuits, the corresponding line voltage input at the detection of zero crossing by the interface circuit;
- the detection of zero crossing being performed independent of the drive signal.
Dependencies are inferred from the claim text.