Magnetic Core Current Balancing in Parallel Circuit Breakers
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Solution Overview
Problem
Parallel-connected circuit breaker arrangements experience current imbalance due to circulating currents, leading to thermal issues and unequal current sharing between poles, caused by differences in mutual coupling with other phases.
Innovation Solution
Incorporating a magnetic core, such as a ring of laminated grain-oriented steel, adjacent to the conductors to introduce inductance and balance currents, with the core partially surrounding the conductors to reduce circulating currents and prevent undesirable heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple circuit breaker switches are connected in parallel to increase current capacity, then the current carrying capability is improved, but current sharing becomes unequal between switches
Solution Approach 1:
The patent applies local quality by introducing different inductance values in specific phases through magnetic cores. Phase A has a magnetic core with higher inductance, while Phase B has no magnetic core or a different core, creating localized impedance differences that balance the current distribution across parallel switches.
Solution Approach 2:
The patent changes the electrical parameter (inductance) by introducing magnetic cores with different characteristics in different phases. This parameter modification creates unequal impedance paths that compensate for the inherent current sharing imbalance in parallel-connected circuit breakers.
2Power
If parallel-connected breaker switches are used, then current capacity is increased, but circulating currents cause thermal issues
Solution Approach 1:
By modifying the inductance parameter in specific phases through magnetic cores, the patent changes the impedance characteristics to eliminate circulating currents, thereby preventing the thermal problems that would otherwise result from unequal current sharing.
3Manufacturing precision
If magnetic core is added to balance currents, then current distribution becomes more even, but device complexity increases
Solution Approach 1:
Instead of adding magnetic cores to all phases, the patent applies them only where needed (e.g., only Phase A or only Phase B), creating local improvements without uniformly increasing complexity throughout the entire system.
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 magnetic core effectively balances currents between poles, reducing thermal problems and achieving more even current distribution by introducing inductive impedance, thus mitigating the effects of circulating currents and temperature imbalances.
Implementation Method 1
positioning at least one magnetic core adjacent at least one of the first and second conductors to introduce an inductance in the at least one of the first and second conductors
Data Source
AI summary
Currents may be balanced in an apparatus including first and second conductors electrically connected to a third conductor and configured to be coupled to respective first and second parallel-connected circuit breaker switches using at least one magnetic core positioned adjacent at least one of the first and second conductors to introduce an inductance in the at least one of the first and second conductors. The at least one core may include at least one magnetic material ring that at least partially surrounds the at least one of the first and second conductors. The at least one magnetic material ring may include a plurality of laminated layers of grain-oriented steel.