Current-Limiting Circuit Breaker with Varistor Arc Suppression
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Solution Overview
Problem
Existing current limiting circuit breakers are not suitable for breaking short circuits between the limiter block and branch circuit breakers, leading to inefficiencies in current limitation and potential damage.
Innovation Solution
A current limiting circuit breaker with switch means in series on the electrical circuit, connected to control means for opening after short-circuit identification and automatically closing after a predetermined duration, and a voltage-dependent resistor for energy dissipation, along with sectioning means for additional control and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If switch means are opened to limit short-circuit current, then current limitation is achieved, but electric arcs may form between contacts
Solution Approach 1:
A voltage-dependent resistor is introduced as an intermediary element connected in parallel with the switch means. When the switch opens during a short-circuit, the voltage-dependent resistor provides an alternative current path that prevents electric arc formation between the switch contacts while still limiting the short-circuit current to a safe level.
2Object-affected harmful factors
If the circuit is opened during a short-circuit, then current limitation is achieved, but the entire circuit including healthy feeders is de-energized
Solution Approach 1:
The circuit is segmented into the faulty feeder and healthy feeders. The voltage-dependent resistor is connected in parallel with the switch means so that when a short-circuit occurs on one feeder, only the affected circuit path is limited while other feeders remain energized and operational, maintaining continuity of service for healthy loads.
3Speed
If switch means open quickly to limit current, then current limitation speed is improved, but energy stored in the circuit must be dissipated
Solution Approach 1:
The voltage-dependent resistor converts the harmful stored energy in the circuit during a short-circuit into a beneficial function. When the switch opens quickly to limit current, the voltage-dependent resistor dissipates the stored energy through controlled resistance, preventing dangerous voltage spikes and protecting the circuit while maintaining the fast opening speed benefit.
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
Effectively limits and manages short-circuit currents, ensuring selective tripping and continuity of service by isolating faults without damaging the circuit, while preventing electric arcs and ensuring safe re-energization of healthy feeders.
Implementation Method 1
at least one element voltage dependent resistor connected in parallel with said switch means for dissipating energy stored in said circuit when the switch means is in an open state
Data Source
Figure 1
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AI summary
The breaker (1) has switch units (8) placed in series on an electrical circuit (10) and connected to a control unit (15) to open the circuit after identification of short circuit current and to automatically close the circuit after a preset duration. A varistor (17) is connected in parallel to the switch units for dissipating energy stored in a circuit when the switch units are in open state. A disconnector (55) is placed between an incoming line and one of the switch units and connected to the control unit. The control unit disconnects the circuit after an identification of the current. An independent claim is also included for a method for limiting current circulating in an electric circuit between an incoming line of a head circuit breaker and an outgoing line equipped with a circuit breaker and/or divisional contactor.