Half-Step Stepper Motor Driving for Lower Peak Current
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Solution Overview
Problem
Existing HVAC systems face challenges in efficiently controlling stepper motors due to the high global warming potential of refrigerants like R-134a, which requires more powerful stepper motors and larger electric currents, leading to difficulties in upgrading or replacing driver circuits.
Innovation Solution
The system controls two or more stepper motors by limiting the number of stator windings energized at a time, thereby reducing peak currents supplied by the driver circuit. This is achieved through a control assembly that applies specific electric signals to the windings of the motors in a half-step mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If more powerful stepper motors are employed to accommodate increased mechanical forces and torque, then the motors can handle higher loads, but larger electric currents are required which makes driver circuit upgrades or replacements difficult
Solution Approach 1:
The patent applies partial action by energizing only one stator winding at a time instead of multiple windings simultaneously. This reduces the peak current demand on the driver circuit while still providing sufficient torque for the stepper motor to handle increased mechanical forces. The control method selectively activates individual windings in sequence, achieving the necessary mechanical output without requiring a high-capacity driver circuit.
2Power
If driver circuits with higher rating are used to supply larger electric currents, then more powerful stepper motors can be driven, but the driver circuits are permanently built into the system making upgrades or replacements difficult
Solution Approach 1:
The patent changes the operational parameters of the stepper motor control by implementing a half-step mode where windings are energized sequentially rather than simultaneously. This parameter change reduces the peak current requirement, allowing the system to use lower-rated driver circuits that are easier to replace and upgrade. The control assembly modifies the electrical parameters (current timing and distribution) to achieve the desired mechanical performance with reduced electrical demands.
3Force
If multiple stator windings are energized at the same time to control torque, then the amount of torque can be controlled, but the peak currents supplied by the driver circuit increase
Solution Approach 1:
The patent implements periodic action by energizing stator windings in a sequential, time-based sequence rather than simultaneously. The control assembly activates one winding at a time in a predetermined sequence, creating periodic torque pulses that accumulate to achieve the desired rotational motion. This temporal separation of winding activation reduces peak current demands while maintaining effective torque control through the cumulative effect of sequential winding engagement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the peak currents provided by the driver circuit, making it easier to manage and upgrade the system without significant changes to the HVAC design, while also potentially reducing the environmental impact associated with high global warming potential refrigerants.
Implementation Method 1
stepper motors are often employed to control flow through such circuits. More specifically, stepper motors set the positions of valves within such circuits, thereby controlling flow through the valves and ultimately through the circuits. A driver circuit connected to a controller can be used to supply such stepper motors with electric currents.
Data Source
AI summary
An HVAC system comprising: an appliance; a control assembly; a first motor; and a second motor. The control assembly: applies a electric signal to the first terminal of the first winding of the first motor for a number of intervals of time; afterwards, apply a second signal to the first terminal of the first winding; apply the first electric signal to the first terminal of the second winding for a second number of regular intervals of time; and after the application of the first electric signal to the first terminal of the second winding, apply the second electric signal to the first terminal of the second winding of the second motor; wherein the first number of regular intervals of time and the second number of regular intervals of time differ by one regular interval of time.