Bare-Wire Flow Heater Control for Leakage Current Limits
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Solution Overview
Problem
Existing electric bare wire instantaneous water heaters face issues with leakage currents due to the potential difference between the bare wire and conductively connected water channels, leading to potential overheating and damage, which current conductivity measurement methods only address by switching off the heating coil in case of lack of water, not effectively managing leakage currents.
Innovation Solution
A control device that determines a hypothetical leakage current based on conductivity values and design-related parameters, reducing heating power by adjusting the operating voltage or switching off the heating device if the leakage current exceeds a predetermined threshold, using a conductivity measuring device and temperature sensors to maintain a specified leakage current threshold at a defined reference temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductivity measurement is used to detect lack of water, then heating coil destruction is prevented, but leakage current management is insufficient
Solution Approach 1:
The control device continuously measures water conductivity and uses this feedback to dynamically adjust heating power. The evaluation unit calculates hypothetical leakage current based on conductivity values and device parameters, creating a closed-loop control system that responds to changing water conditions to manage both overheating and leakage current risks
Solution Approach 2:
The system changes the heating power parameter based on measured conductivity values. By adjusting the operating voltage or switching off the heating device when conductivity indicates high leakage risk, the system adapts its operation to maintain safety margins while preventing both coil destruction and excessive leakage currents
2Object-generated harmful factors
If heating power is reduced to manage leakage current, then safety compliance is improved, but heating efficiency decreases
Solution Approach 1:
The control device applies partial heating power reduction rather than complete shutdown when leakage current thresholds are approached. By reducing heating power proportionally to the calculated leakage risk, the system maintains sufficient heating performance while staying within safety limits, avoiding excessive restriction of useful action
Solution Approach 2:
The heating power is dynamically adjusted based on real-time conductivity measurements and calculated leakage current. The system transitions from static on/off control to continuous dynamic modulation, allowing optimal heating efficiency at low leakage risk while automatically reducing power when safety thresholds are approached
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
Precisely manages leakage currents by reducing the heating output when the leakage current exceeds the threshold, preventing overheating and potential damage, while ensuring compliance with safety limits by accounting for water temperature and conductivity variations.
Implementation Method 1
a conductivity measuring device for determining a conductivity value of the water flowing through the channel arrangement
Implementation Method 2
one for heating water flowing through the channel arrangement water-equipped electric bare wire heating device
Data Source
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AI summary
The present invention relates to an electric bare wire instantaneous water heater (10) for hot water preparation, comprising a duct arrangement (11) with an electrically conductive water inlet duct (12) which is electrically conductively connected to ground potential and which is set up for connection to a first external water supply line and a electrically conductive water drainage channel (13) which is electrically conductively connected to ground potential and which is set up for connection to a second external, water-discharging water line, the channel arrangement (11) comprising at least one electrically non-conductive water-carrying channel (14) on whose The water inlet channel (12) and the water outlet channel (13) are arranged at each channel end, an electric bare wire heating device (15) designed to heat water flowing through the channel arrangement (11), an electronic control device designed to regulate the heating output of the bare wire heating device (15), wherein the control device comprises a conductivity measuring device for determining a conductivity value of the water flowing through the channel arrangement (11) and is characterized in that the control device comprises an evaluation unit set up to determine a hypothetical leakage current value on the basis of the conductivity value and at least one predetermined, design-related device parameter and the Control device is adapted to reduce the fleet power of the bare wire heating device (15) if the hypothetical leakage current value exceeds a predetermined leakage current threshold value. Furthermore, the present invention relates to a method for controlling an electric bare wire flow heater.