Contactor Coil Temperature Evaluation via Resistance Measurement
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Solution Overview
Problem
Electrical contactors face temperature-related malfunctions due to overheating, which can lead to contact welding and blocking, and existing temperature monitoring methods using sensors are costly and inaccurate, measuring local temperatures that do not reflect the coil temperature effectively.
Innovation Solution
A method to evaluate the temperature of a contactor's actuation coil by determining its resistance through controlled voltage and current measurements, without the need for additional sensors, by applying a closing order to set a standard current, sending a drop-out order, measuring the current decay, and analyzing the resistance to calculate the coil temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature detector is used to monitor the temperature of a contactor, then the temperature can be measured, but the measurement is local and does not accurately reflect the coil temperature
Solution Approach 1:
The patent replaces the mechanical/physical temperature sensor system with an electrical measurement system. Instead of using a temperature detector that physically contacts the coil, the system measures electrical parameters (current, voltage, resistance) of the coil to infer temperature. This substitution enables accurate coil temperature measurement without the limitations of local temperature sensors.
2Reliability
If a temperature detector is implemented in the contactor, then temperature monitoring is possible, but additional costs are incurred that are often prohibitive for industrial use
Solution Approach 1:
The contactor uses its own existing electrical components (coil, measuring means already present in the circuit) to perform temperature monitoring. The system leverages the coil's electrical characteristics and existing voltage/current measurement infrastructure, eliminating the need for separate temperature detection hardware. This self-service approach provides temperature monitoring without adding external sensors or increasing device complexity.
3Ease of operation
If the control voltage is applied to the contactor, then the contactor operates, but the temperature-dependent electrical resistance causes difficulty in closing the power contacts
Solution Approach 1:
The system performs preliminary temperature evaluation by measuring electrical parameters before the contactor closing operation. By assessing the coil temperature in advance using the electrical measurement method, the system can determine whether conditions are suitable for closing, preventing operation at temperatures that would cause malfunction. This preliminary check ensures safe operation before the actual closing action occurs.
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 method accurately evaluates the coil temperature, preventing overheating-related malfunctions by determining the resistance of the actuation coil, thereby ensuring reliable operation without the need for additional sensors, reducing costs and improving accuracy.
Implementation Method 1
an electromagnetic actuator having a magnetic yoke and a movable ferromagnetic core, means for controlling an actuation coil
Implementation Method 2
the dynamic behavior of the moving part of the contactor depends on the electrical resistance of the coil. But this depends on the temperature
Data Source
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AI summary
The method involves sending a closing order by applying voltage to terminals (L1, L2) of an actuating coil (3) for enabling electric current (I) flowing in the coil to be modified up to a reference value. A drop-out order is sent by fixing a drop-out voltage at the terminals of the actuating coil. The electric current flowing in the coil is measured, and acquisition of specific values on a signal of the electric current is performed. The specific values are analyzed for evaluating operating temperature of the coil. An independent claim is also included for a contactor.