Transductor Circuit for DC Trip Accuracy
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Solution Overview
Problem
Current DC circuit breakers face challenges in photovoltaic applications due to low short circuit current levels, where thermal and magnetic trip units are not suitable, and DC electronic trip units are costly, while AC electronic trip units are inoperable with DC current.
Innovation Solution
An electrical switching apparatus with a transductor circuit that converts direct current to alternating current, enabling an AC electronic trip circuit to control separable contacts, providing enhanced tripping accuracy and cost-effectiveness for DC applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a DC electronic trip unit is used in DC circuit breakers, then tripping accuracy and control are enhanced, but the cost increases significantly compared to AC electronic trip units
Solution Approach 1:
The patent introduces a transductor circuit as an intermediary device that converts DC current to AC current. This AC current can then be processed by standard AC electronic trip units, which are cost-effective and readily available. The transductor acts as a mediator that bridges the gap between DC applications and AC-based protection technology, achieving both accuracy and cost-effectiveness.
Solution Approach 2:
The invention changes the electrical parameter of the current from DC to AC through the transductor circuit. By converting the DC current to AC current, the system can utilize AC electronic trip units that have optimized performance and lower cost. This parameter transformation enables the use of mature AC technology in DC applications.
2Ease of manufacture
If AC electronic trip units are used in DC applications, then cost is reduced and availability is improved, but the units become inoperable without a time varying magnetic field
Solution Approach 1:
The transductor circuit serves as an intermediary that generates the required time-varying magnetic field from DC current. This enables AC electronic trip units to operate in DC applications by providing them with the AC signal they require, while the actual protected circuit remains DC. The transductor mediates between the DC source and the AC-based trip unit.
Solution Approach 2:
The invention replaces the need for a physical DC-to-AC conversion mechanism within the trip unit itself with an external transductor circuit. This substitution allows the use of standardized AC electronic trip units in DC applications, leveraging their cost advantages and availability while maintaining operational reliability through the transductor's current conversion capability.
3Reliability
If thermal trip units are used in photovoltaic applications with low short circuit current, then nuisance tripping is reduced, but the tripping time becomes excessively long and protection is inadequate
Solution Approach 1:
The patent replaces the mechanical thermal trip mechanism with an electronic trip unit that processes electrical signals. The transductor converts DC current to AC current, which is then processed by the AC electronic trip unit to provide fast, accurate tripping decisions. This substitution eliminates the inherent time delays of thermal mechanisms while maintaining reliability.
4Speed
If magnetic trip units are used in photovoltaic applications with low short circuit current, then instantaneous tripping is achieved, but calibration becomes difficult and excessive nuisance tripping occurs
Solution Approach 1:
The invention replaces the magnetic trip mechanism with an AC electronic trip unit that processes the transductor's AC output signal. This electronic approach provides precise, programmable trip thresholds that are easy to calibrate and adjust, eliminating the calibration difficulties and nuisance tripping issues associated with magnetic units while maintaining instantaneous tripping capability.
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
The solution offers precise and economical circuit protection in DC applications by using an AC electronic trip circuit, which is more accurate and cost-effective than traditional thermal and magnetic trip units, while being compatible with both AC and DC systems.
Implementation Method 1
a transductor circuit that senses a direct current between at least one of the input terminals and at least one of the output terminals and outputs an alternating current proportional to the direct current
Data Source
AI summary
An electrical switching apparatus includes a transductor circuit that senses a direct current between at least one input terminal and at least one output terminal and outputs an alternating current proportional to the direct current between the input terminal and the output terminal. The electrical switching apparatus also includes an alternating current electronic trip circuit configured to control pairs of separable contacts to separate based on the alternating current output from the transductor circuit. The alternating current electronic trip circuit includes a rectifier circuit, an interface circuit, and a processor structured to output a control signal to control a trip actuator to cause an operating mechanism to separate the plurality of pairs of separable contacts.