Solenoid Coil Current Switching for Lower Hold Power
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Solution Overview
Problem
Conventional solenoid coil designs in HVAC systems face issues with high steady state power consumption and operating temperatures, leading to increased heat rise and the need for higher insulation class wires, which restricts performance and requires multiple coils for various voltages and frequencies.
Innovation Solution
A control circuit that applies two different current values to a DC solenoid coil, with a higher pick current for actuation and a lower hold current for maintenance, actively and electronically controlled, allowing operation over a wide voltage range and reducing power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC solenoid coil is sized to provide sufficient pick current for actuation, then the solenoid can be actuated reliably, but the steady state power consumption and operating temperature increase
Solution Approach 1:
The patent applies dynamics by transitioning from a static single-current design to a dynamic two-current design. The control circuit switches between a higher pick current for actuation and a lower hold current for maintaining the solenoid position, allowing the system to adapt current levels based on operational phase. This dynamic current adjustment resolves the contradiction by providing high current only when needed for actuation while reducing current during steady state operation.
Solution Approach 2:
The patent implements periodic action through time-based current switching. A control circuit applies the higher pick current for a predetermined time period during actuation, then switches to the lower hold current for maintaining the solenoid position. This periodic alternation between high and low current states allows reliable actuation while minimizing steady state power consumption.
2Reliability
If a DC solenoid coil is sized to provide sufficient pick current for actuation, then the solenoid can be actuated reliably, but the operating temperature and heat rise increase
Solution Approach 1:
The dynamic two-current operation allows the solenoid to experience high current only briefly during actuation rather than continuously, reducing the average power dissipation and resulting heat generation. This dynamic approach maintains actuation reliability while lowering operating temperature.
Solution Approach 2:
The patent converts the potentially harmful continuous high current (which causes excessive heat) into a beneficial brief high-current pulse for actuation followed by low-current operation. The harmful thermal effect is transformed by timing the high current application only when mechanically necessary for overcoming the air gap, turning a thermal problem into a controlled actuation solution.
3Temperature
If higher insulation class wires are used to handle increased operating temperatures, then the solenoid can operate at higher temperatures, but the material costs and device complexity increase
Solution Approach 1:
The patent converts the thermal stress problem into a manageable transient condition. By limiting high current to brief actuation periods rather than continuous operation, the resulting temperature excursions are reduced and transient in nature, allowing the use of standard insulation class wires rather than requiring higher insulation class materials.
Solution Approach 2:
The patent changes the temporal parameter of current application from continuous to intermittent. This parameter change reduces the thermal load on the wire insulation, allowing standard insulation classes to handle the reduced average temperature and transient thermal stress without requiring more complex high-temperature insulation materials.
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 solution reduces heat from power dissipation, enables the use of smaller solenoid coils, lowers operating temperatures, and decreases energy consumption, while allowing for increased Maximum Operating Pressure Differential and reduced material costs.
Implementation Method 1
A voltage may be output to a solenoid coil to actuate a valve in an HVAC system. The solenoid coil may be actuated using an opening magnetic force and a holding magnetic force.
Implementation Method 2
The solenoid coil may be actuated using an opening magnetic force and a holding magnetic force. Solenoid force versus stroke curves indicate that the force generated by a magnetic solenoid actuator is lowest when the magnetic air gap is the largest.
Data Source
AI summary
Disclosed are exemplary embodiments of control circuits for supplying current to actuate solenoids, such as refrigerant valves in HVAC systems, other valves, “solenoid” style contactors, other coil driven actuators, etc. In exemplary embodiments, a control circuit for supplying current to actuate a solenoid comprises a solenoid coil and a switch coupled with the solenoid coil. The control circuit may be configured such that the solenoid coil is operable as a load coil and a switch mode supply coil and such that the switch is configured to operate a load and power supply of the control circuit. Additionally, or alternatively, the control circuit may include a current monitoring shunt and a flyback diode that are located in a circulating current loop defined by and/or including the solenoid coil, the current monitoring shunt, and the flyback diode.