Relay Coil Voltage Regulation for Temperature Compensation
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Solution Overview
Problem
Electromechanical relays and contactors face issues with maintaining a consistent magnetic field over a wide temperature range due to varying coil resistance, leading to inadequate actuation, prolonged arcing, or excessive force on contacts, as the current supplied by fixed voltage sources changes with temperature.
Innovation Solution
An adjustable voltage regulator system that uses a temperature sensing device, such as a thermistor, to adjust the voltage applied to the coil, maintaining a constant current magnitude by compensating for changes in coil resistance through a voltage divider circuit, ensuring a consistent magnetic field across temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed voltage source is used to power the coil, then the circuit is simple and easy to operate, but the coil current varies with temperature causing inconsistent magnetic field strength
Solution Approach 1:
The patent implements a feedback control system where the temperature sensing device continuously monitors coil temperature and automatically adjusts the voltage applied to the coil through the voltage regulator. This closed-loop feedback mechanism compensates for temperature-induced resistance changes, maintaining consistent coil current and magnetic field strength while eliminating the need for manual intervention.
Solution Approach 2:
The patent replaces manual voltage adjustment mechanisms with an automated electronic control system comprising a temperature sensing device, voltage regulator, and control circuitry. This substitution of mechanical/manual systems with electronic automation maintains ease of operation while achieving precise control over coil current regardless of temperature variations.
2Temperature
If the coil operates at high temperature, then the resistance increases reducing current, but the magnetic field becomes too weak causing prolonged arcing or failure to actuate
Solution Approach 1:
The patent applies preliminary anti-action by detecting temperature increases before they cause harmful effects and preemptively adjusting the voltage to compensate. The control circuit monitors coil temperature and, upon detecting elevated temperatures that would reduce current below the threshold needed for reliable actuation, automatically increases the applied voltage to maintain sufficient magnetic field strength and prevent arcing or actuation failure.
Solution Approach 2:
The patent dynamically changes the voltage parameter applied to the coil based on temperature conditions. The voltage regulator adjusts the voltage level in response to temperature sensing device readings, increasing voltage when temperature rises to compensate for increased resistance, thereby maintaining constant coil current and magnetic field strength across the full temperature range.
3Temperature
If the coil operates at low temperature, then the resistance decreases increasing current, but the magnetic field becomes too strong causing excessive force on contacts and exceeding power budget
Solution Approach 1:
The patent applies preliminary anti-action by detecting low temperature conditions before they cause excessive current flow. The control circuit monitors coil temperature and, upon detecting temperatures that would reduce resistance and increase current beyond safe levels, preemptively reduces the applied voltage to prevent excessive magnetic field strength, contact damage, and power budget overruns.
Solution Approach 2:
The patent dynamically changes the voltage parameter applied to the coil based on temperature conditions. The voltage regulator decreases the voltage level in response to low temperature readings from the sensing device, compensating for reduced resistance and preventing excessive coil current, thereby maintaining safe and consistent operating conditions across the full temperature range.
4Reliability
If temperature compensation is implemented, then the magnetic field consistency is improved, but the device complexity increases
Solution Approach 1:
The patent introduces a temperature sensing device as an intermediary component that bridges the gap between temperature conditions and voltage control. This intermediary sensor provides temperature information to the control circuit, which then translates it into appropriate voltage adjustments through the voltage regulator, achieving precise temperature compensation while keeping the overall system architecture simple and modular.
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 provides a consistent magnetic field for reliable actuation of electromechanical relays and contactors, preventing under- or over-driving, and allows for predictable current and power allocation within a defined budget, thereby reducing the risk of arcing, welding, or contact damage.
Implementation Method 1
The coil resistance varies with the temperature of the coil exhibiting a positive temperature coefficient which causes the coil resistance to increase as the temperature of the coil wire increases
Implementation Method 2
The regulated voltage output from the voltage regulator is coupled to a first terminal of the coil and to a first terminal of a voltage divider. The voltage divider is comprised of an impedance and the temperature sensing device. The voltage divider has a midpoint at a junction of the impedance and the temperature sensing device at which a midpoint voltage is developed. The midpoint voltage is provided as the variable control voltage to the voltage regulator.
Implementation Method 3
The voltage divider is comprised of an impedance and the temperature sensing device. The voltage divider has a midpoint at a junction of the impedance and the temperature sensing device at which a midpoint voltage is developed.
Implementation Method 4
The strength of a magnetic field operating an electromechanical relay or contactor is a function of the product of the number of turns of the coil wire and the magnitude of the current, measured in amperes, passing through the coil wire.
Data Source
Figure 1~2
Figure 3
AI summary
A circuit and method for controlling a voltage applied to a coil 102 to actuate electromechanical relays or contactors. The strength of a magnetic field operating the coil is a function of the product of the number of turns of the coil wire and the magnitude of current passing through the coil wire. An adjustable voltage regulator 104 provides a regulated voltage at an output 112 to a first terminal 120 of the coil to energize the coil based on the temperature of the coil as sensed by a temperature sensing device 124 located proximate the coil. The regulated voltage is controlled based on the sensed coil temperature to consistently provide a current of optimal magnitude to actuate the coil at the sensed temperature. A transient voltage suppression circuit 134,136 may be used with the coil to suppress back electromotive force generated currents and voltages when the coil is de-energized.