Current Transformer Power Stealing for Solid-State Relay Control
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Solution Overview
Problem
In applications where there is no continuous source of power for the circuit controlling solid-state relay switches, the control circuit for the solid-state relay may not function properly due to the unavailability of voltage when the relay is turned on.
Innovation Solution
A circuit is designed with a first rectifier, a bridge circuit, and a second rectifier, where the bridge circuit is coupled to the output of the first rectifier and adapted to be coupled to a primary winding of a transformer, and the second rectifier input is adapted to be coupled to a secondary winding of the transformer, enabling power to be derived from the transformer windings to maintain the operation of the solid-state relay control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the solid-state relay is turned on to switch the load, then the load is activated, but the voltage across the solid-state relay switches drops to approximately zero volts making power unavailable for the control circuit
Solution Approach 1:
A current transformer is introduced as an intermediary device to transfer power from the load circuit to the control circuit. The transformer's primary winding couples to the solid-state relay switches, and the secondary winding provides isolated power to the control circuit through rectification, enabling the control circuit to remain powered even when the relay is on
Solution Approach 2:
The control circuit powers itself by deriving energy from the load current through the current transformer. The rectifier circuit converts the transformer output to DC, creating a self-sustaining power supply that eliminates the need for external power sources
2Reliability
If the control circuit is powered from the voltage generated by the transformer secondary winding, then the control circuit can function, but the voltage becomes unavailable when the relay is turned on
Solution Approach 1:
The rectifier circuit continuously converts the AC voltage from the transformer secondary winding into DC voltage, maintaining continuous power supply to the control circuit regardless of the relay state. This ensures uninterrupted operation of the control circuit throughout the relay's on/off cycles
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 ensures that the solid-state relay control circuit remains powered regardless of the on/off state of the solid-state relay, preventing improper functioning due to voltage unavailability and extending the operational duration by utilizing power from the transformer windings.
Implementation Method 1
a voltage generated by a secondary winding of a transformer, whose primary winding is coupled across the switches of the solid-state relay
Implementation Method 2
The second rectifier input is adapted to be coupled to a secondary winding of the transformer
Data Source
AI summary
A circuit includes a first rectifier having a first rectifier input and a first rectifier output. The circuit also includes a bridge circuit and a second rectifier. The bridge circuit is coupled to the first rectifier output. The bridge circuit has first, second, third, and fourth terminals. The first and second terminals are coupled to the first rectifier output, and the third and fourth terminals are adapted to be coupled to a primary winding of a transformer. The second rectifier has a second rectifier input and a second rectifier output. The second rectifier input is adapted to be coupled to a secondary winding of the transformer.