Light Fixture Safety Loop Using Low-Voltage Thermo Switch
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Solution Overview
Problem
Existing light fixture safety systems require high-current switching, which reduces the lifespan of thermo switches and increases production costs, and may not provide immediate power disconnection in case of temperature overload.
Innovation Solution
A low-voltage safety loop with a constant current source and current measuring device is used, allowing small thermo switches to manage limited current, enabling efficient temperature supervision and immediate power disconnection through a direct connection to the power supply, reducing costs and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional high-current thermo switches are used for temperature supervision, then the light fixture can be protected from overheating, but the thermo switch lifespan is reduced and production costs increase
Solution Approach 1:
A low-voltage safety loop with constant current source (e.g., 10-20mA) is introduced as an intermediary system. The thermo switch operates in this isolated low-voltage loop rather than directly switching high lamp current. The safety loop includes a current source, thermo switch, and current measuring device that triggers power interruption when the thermo switch opens due to temperature overload.
Solution Approach 2:
The electrical system is segmented into two independent circuits: the high-voltage lamp power circuit and the low-voltage safety supervision circuit. The thermo switch belongs to the safety circuit and only handles minimal supervising current, while the lamp circuit handles the full lamp current. This segmentation allows the thermo switch to function without being exposed to high current stress.
2Reliability
If traditional high-current thermo switches are used for temperature supervision, then the light fixture can be protected from overheating, but production costs increase
Solution Approach 1:
A low-voltage safety loop with constant current source (e.g., 10-20mA) is introduced as an intermediary system. The thermo switch operates in this isolated low-voltage loop rather than directly switching high lamp current. The safety loop includes a current source, thermo switch, and current measuring device that triggers power interruption when the thermo switch opens due to temperature overload.
Solution Approach 2:
The invention uses inexpensive low-voltage components in the safety loop that can be easily replaced if needed. The thermo switch in the safety loop handles minimal current and can be a simple, low-cost component compared to high-current rated switches. The constant current source and measuring device are also low-power, low-cost components.
3Duration of action of moving object
If a safety loop with constant current source and current measuring device is used, then thermo switch lifespan is extended and production costs are reduced, but the system complexity increases
Solution Approach 1:
The safety loop components serve multiple functions: the constant current source provides both the supervising current and a reference for the measuring device; the current measuring device both monitors the loop current and triggers the power interruption; the thermo switch both supervises temperature and acts as the failure indicator. This multi-functionality reduces the number of separate components needed.
Solution Approach 2:
The safety loop is self-monitoring and self-actuating. The constant current source automatically maintains the supervising current, and when the thermo switch opens due to temperature overload, the current measuring device automatically detects the current interruption and triggers the power supply to interrupt the lamp current without requiring external control logic or additional sensors.
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 extends the lifespan of thermo switches, reduces production costs, and ensures rapid power disconnection in case of temperature overload, enhancing the safety and reliability of light fixtures.
Implementation Method 1
a temperature-sensitive switch responsive to the ambient temperature
Implementation Method 2
a current source that generates a constant current in the safety loop
Implementation Method 3
which safety loop is supervised by current measuring device
Data Source
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AI summary
The present invention relates to a light fixture and a method for control of a light fixture is supervised by at least one thermo switch, which thermo switch by increasing temperature protects the light source by disconnecting the power supply to the light source. It is the object of the invention to achieve a safety circuit in a light fixture without switching the supply circuit to a light source. This can be achieve in a light fixture by using at least one thermo switch, which can be connected to a low voltage safety loop, which safety loop can be connected to a current source that generates a constant current in the safety loop, which safety loop is supervised by current measuring device. Hereby it is achieved that the switching, if temperature arises, is achieved by switching contacts that are only carrying a very limited current. This will increase the life time of the thermo switch and very small switches can be used.