Transformer-Based Temperature Detection for High-Voltage Heating Elements
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Solution Overview
Problem
Conventional temperature detection methods for high-voltage heating elements face challenges in accurate and timely temperature measurement due to insulation requirements, which complicate the detection process and introduce time lags, especially when using thermostats or thermistors directly attached to these elements.
Innovation Solution
A temperature detection apparatus utilizing a transformer with a thermostat or thermistor directly attached to the heating element, where the thermostat's contacts short-circuit or open-circuit based on temperature, and a current detection circuit generates an alarm signal when a preset current threshold is exceeded, allowing for direct attachment and reducing insulation-related errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermostat or thermistor is attached directly to a heating element operating at high voltage, then temperature detection accuracy is improved, but the detecting circuit becomes complicated due to insulation requirements
Solution Approach 1:
The patent divides the detection system into two separate circuits: a high-voltage detection circuit that directly contacts the heating element for accurate temperature sensing, and a low-voltage control circuit that processes the detection signals. The isolation transformer segments the electrical isolation function from the detection function, allowing direct attachment of the thermostat to the heating element without compromising safety or requiring complex insulation in the control circuit.
Solution Approach 2:
The patent introduces an isolation transformer as an intermediary device between the high-voltage detection circuit and the low-voltage control circuit. This transformer mediates the signal transmission while providing electrical isolation, enabling accurate temperature detection from the high-voltage environment without exposing the control circuit to high voltage, thus avoiding the need for complex insulation designs.
2Reliability
If an insulator is interposed between the heating element and the thermostat, then high voltage insulation is achieved, but temperature measurement accuracy deteriorates and time lag increases
Solution Approach 1:
The patent separates the insulation function from the thermal coupling function by creating two distinct circuits. The high-voltage detection circuit achieves insulation through circuit topology and transformer isolation rather than physical insulators between the thermostat and heating element. This segmentation allows the thermostat to maintain direct thermal contact with the heating element for accurate measurement while the electrical insulation is provided by the isolated circuit design.
3Device complexity
If the detecting circuit is operated at high voltage to eliminate insulation needs, then device complexity is reduced, but safety hazards increase due to direct connection with low-voltage control circuits
Solution Approach 1:
The patent segments the system into a high-voltage detection circuit and a low-voltage control circuit that are electrically isolated from each other. The high-voltage circuit operates at elevated voltages for detection purposes without requiring complex insulation structures, while the low-voltage control circuit maintains safety by being isolated through the transformer. This segmentation eliminates safety hazards while avoiding the need for complicated insulation designs.
Solution Approach 2:
The isolation transformer serves as an intermediary that allows the detection circuit to operate at high voltage while protecting the low-voltage control circuit. The transformer transfers detection signals from the high-voltage side to the low-voltage side without direct electrical connection, eliminating safety hazards associated with high voltage exposure in the control circuit while maintaining operational simplicity.
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 configuration enables precise and timely temperature detection of high-voltage heating elements, simplifying the detection process and reducing errors caused by insulation, while using general-purpose components for cost-effectiveness and miniaturization.
Implementation Method 1
a transformer; a thermostat attached directly to an electrically conductive site of the heating element... having contacts that become short-circuited or come into an open-circuit condition... the contacts being connected to a secondary coil in the transformer
Implementation Method 2
a thermostat attached directly to an electrically conductive site of the heating element and having contacts that become short-circuited or come into an open-circuit condition depending on whether or not the temperature of the heating element is equal to or higher than a predetermined value
Implementation Method 3
a thermistor attached directly to an electrically conductive site of the heating element and having a resistance value varying depending on the temperature of the heating element
Implementation Method 4
a current detection circuit detecting a current value of current flowing through the primary coil in the transformer, and outputs an alarm signal when the current value exceeds a preset value
Data Source
AI summary
A temperature detection apparatus includes a transformer, a thermostat attached directly to an electrically conductive site of the heating element and has contacts that become short-circuited or come into an open-circuit condition depending on whether or not the temperature of the heating element is equal to or higher than a predetermined value, the contacts being connected to a secondary coil in the transformer, a DC voltage source and a transistor configured to supply required AC power to a primary coil in the transformer, a current detection resistor configured to detect a current flowing through the primary coil in the transformer, and a comparison circuit detecting a voltage generated across the current detection resistor when a current flows through the current detection resistor, the comparison circuit outputting an alarm signal when the current flowing through the primary coil in the transformer exceeds a preset threshold current.