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Technical Note: This article is an interpretation of the referenced research paper. The figures, simulation results, experimental waveforms, and technical data presented herein are reproduced from the original research source for technical interpretation and discussion. Please refer to the original publication for the complete methodology and results.
An air circuit breaker (ACB) does more than simply separate its contacts during a short-circuit event.
Once the contacts open, an electrical arc is established and must be driven away from the contact region, transferred to the arc runners, and guided into the arc chute. Inside the arc chute, the arc is divided by splitter plates, cooled, and converted into a series of shorter arcs until interruption is achieved.
But what happens if the arc does not remain inside the splitter plate region?
A research study published in Plasma Science and Technology investigated this question using a three-dimensional magnetohydrodynamic (MHD) model combined with breaking experiments.
The study focused on the transient motion of the arc inside an ACB and, in particular, the influence of the material and position of the innermost barrier plate on arc motion and interruption performance.
The arc chamber is one of the critical structures affecting ACB breaking performance.
When the contacts separate, electromagnetic force and gas flow drive the arc toward the arc runners and splitter plates.
The intended process is:
Contact Separation → Arc Runner → Splitter Plate → Arc Splitting → Cooling → Arc Extinction
Once the arc enters the splitter plate assembly, it is divided into several shorter arcs. This increases the arc voltage and promotes cooling and interruption.
However, the simulation reported in this study shows that arc motion can become unstable.
The arc may move backward toward the contact region, or establish an alternative current path behind the splitter plates.
These phenomena can reduce the effectiveness of the arc chute.
Figure 1. Structure of the ACB arc chamber.
The ACB structure studied in the paper contains the fixed contact, movable contact, left and right arc runners, splitter plates, and vent.
The arc runners provide an electrical path during arc movement, while the splitter plates are responsible for dividing and cooling the arc. The vent provides an airflow passage between the arc chamber and the atmosphere.
The geometry of these components determines how the arc moves after contact separation.
Experimental measurements can provide macroscopic information such as arc voltage and current.
However, the internal state of the arc plasma is much more difficult to observe directly.
The study therefore developed a three-dimensional MHD model to investigate the coupled behavior of the arc plasma, electromagnetic field, and gas flow.
The model considers:
Arc plasma temperature
Gas flow
Current density
Thermal radiation
Electrical conductivity
Thermal conductivity
Viscosity
Magnetic field
Nonlinear magnetic characteristics of ferromagnetic components
The governing model combines mass conservation, momentum conservation, energy conservation, and electromagnetic equations.
The simulation was solved using the FLUENT finite-volume method, with a half-symmetry model used to reduce computational complexity.
This approach allows the researchers to visualize transient parameters that are difficult to obtain experimentally, including temperature distribution, gas flow, and current density.
The simulation identifies five major stages of arc motion:
Arc commutation from the contacts to the arc runner
Arc movement along the arc runner toward the splitter plate
Arc splitting by the splitter plate
Back commutation
Arc burning at the back of the splitter plate
This sequence is important because successful interruption depends not only on whether the arc reaches the splitter plates, but also on whether it remains within the intended arc-splitting path.
Fig.2 Arc temperature distribution sequences with time on the symmetry plane of the arc chamber
Figure 2 provides a time-resolved view of the arc movement.
At the beginning of the process, the arc develops between the contacts and expands along the contact surfaces.
At approximately 0.175 ms, the arc begins to transfer toward the left arc runner.
At approximately 0.390 ms, the arc begins to move toward the right arc runner while the arc on the opposite side has already entered the splitter plate region.
As the surrounding gas is heated, its electrical conductivity increases, affecting the subsequent arc commutation process.
The simulation then reveals a more complex behavior: the arc does not always remain inside the splitter plate region.
As the arc chamber temperature increases, the air around the arc becomes increasingly ionized and electrically conductive.
Under these conditions, an alternative arc path can become established.
At approximately 0.795 ms, back commutation occurs between the movable contact and the left arc runner.
The arc inside the splitter plate region is gradually replaced by the back arc.
The arc subsequently moves back toward the splitter plates, and the process can repeat. Another back commutation occurs at approximately 1.300 ms.
This behavior is important because it can produce fluctuations in arc voltage.
Instead of:
Arc Voltage ↑ continuously
the actual process can become:
Arc enters splitter plate → Voltage rises → Back commutation → Voltage falls → Arc returns → Voltage rises again
The simulation therefore provides an explanation for unstable arc-voltage behavior during interruption.
The most important finding of the simulation appears at approximately 1.700 ms.
The arc has moved through the splitter plate region, but a current channel remains between the innermost barrier plate and the top of the splitter plate.
The arc continues burning in this region.
Fig.3 Temperature and current density distribution of the arc chamber at t = 1.700 ms, (a) Temperature distribution, (b) Current density distribution
Figure 3 shows why this behavior is important.
The temperature distribution indicates that the arc continues burning behind the splitter plate, while the current density distribution reveals a current channel through the gap between the innermost barrier plate and the top of the splitter plate.
In this condition, the arc is no longer effectively divided by the splitter plates.
As a result:
Arc Splitting ↓ → Arc Voltage Rise ↓ → Interruption Effectiveness ↓
The paper therefore identifies arc burning behind the splitter plate as a phenomenon that can weaken the interruption process.
The simulation suggests that the position of the barrier plate has a strong influence on arc motion.
To verify this finding experimentally, the researchers compared different barrier plate configurations during breaking tests.
A single-frequency LC oscillator power circuit was used.
Arc voltage was measured using a high-voltage probe, while arc current was measured using a Rogowski coil. The waveforms were recorded using an oscilloscope.
Fig.4 Principle diagram
During the breaking test, the charged capacitors are discharged through the inductance and specimen to generate the short-circuit current.
This experimental arrangement allows the researchers to record the arc voltage and current during the breaking process.
The electrical waveforms can then be compared with the simulated arc behavior.
This creates an important verification chain:
MHD Simulation → Arc Voltage / Current → Physical Observation
The study compares two configurations under an expected 10 kA short-circuit current peak.
Innermost barrier plate: stainless steel
Gap between barrier plate and splitter plate: 5 mm
Innermost barrier plate: insulating material
Barrier plate positioned close to the top of the splitter plate
The purpose was to investigate how barrier plate material and position influence arc motion and breaking performance.
After contact opening, the arc voltage initially rises as the arc elongates and moves toward the splitter plates.
Once the arc enters the splitter plate region, it is divided into shorter arcs and the arc voltage continues to rise.
However, when back commutation occurs, the arc voltage can fall again.
The waveform therefore contains information about the underlying arc motion.
Fig.5 Arc voltage and current waveforms
The experimental results show a clear difference between the two configurations.
For Condition A, the measured arc voltage peak is approximately:278 V
For Condition B, the arc voltage peak reaches approximately:355 V
The higher voltage obtained under Condition B indicates that the arc is more effectively driven into the splitter plate region and divided there.
The study also associates the fluctuations in the voltage waveform with the back-and-forth movement of the arc.
278 V → Condition A
355 V → Condition B
+27.7% higher reported peak voltage
Note: The percentage above is calculated from the two reported peak values and is not a value explicitly stated by the paper.
Electrical waveforms provide one form of evidence.
The researchers also examined the physical erosion of the vent after the breaking tests.
This provides another way to identify where the arc has actually been burning.
Fig.6 Erosion of the vent
The erosion results are consistent with the simulation and electrical measurements.
Under Condition A, evident erosion appears on the innermost barrier plate and the top of the splitter plate, indicating an arc path in this region.
Under Condition B, no evident erosion is observed.
According to the study, the insulating innermost barrier plate positioned close to the top of the splitter plate can effectively reduce arc burning behind the splitter plate.
This creates a useful three-level verification:
Simulation
→ Current channel behind splitter plate
Experiment
→ Different arc-voltage behavior
Physical inspection
→ Different erosion patterns
The three observations support the same arc-motion mechanism.
The study demonstrates that arc chute performance is not determined by the splitter plates alone.
The surrounding barrier structure also affects the path taken by the arc.
Several design considerations emerge from the research.
The arc needs to transfer effectively from the contacts to the arc runners and into the splitter plate assembly.
If the arc returns toward the contact or runner region, arc voltage can fall and interruption can become less effective.
A gap behind the splitter plate can provide an unintended path for current and arc burning.
The position of the innermost barrier plate influences whether the arc remains within the intended splitting region.
The experimental comparison shows that changing both the material and position of the innermost barrier plate can significantly influence arc voltage and arc burning behavior.
The value of MHD simulation is not simply to generate a colorful temperature map.
Its engineering value is that it helps connect several phenomena that are difficult to observe simultaneously in an experiment:
Arc Motion
↓
Temperature Distribution
↓
Gas Flow
↓
Current Density
↓
Arc Splitting
↓
Arc Voltage
↓
Interruption Behavior
In this study, the simulation identified the possibility of back commutation and arc burning behind the splitter plate.
The subsequent breaking experiments and erosion observations provided experimental evidence supporting these findings.
The study provides several useful insights into ACB arc chamber development:
01 — Arc movement is a dynamic process
Electromagnetic force, gas flow, temperature, and electrical conductivity interact throughout the interruption process.
02 — Reaching the splitter plate is not enough
The arc must remain within the intended splitting path.
03 — Back commutation can weaken interruption
Repeated backward and forward arc movement can produce fluctuations in arc voltage.
04 — The area behind the splitter plate matters
An unintended current channel can allow the arc to burn without effective splitting.
05 — Barrier plate position is a design variable
The study shows that positioning the insulating innermost barrier plate close to the splitter plate promotes arc splitting and increases arc voltage in the tested configuration.
06 — Simulation and experiment complement each other
MHD simulation reveals internal arc behavior, while electrical measurements and erosion observations provide experimental verification.
The research shows that effective ACB arc interruption depends on controlling the complete arc path—not simply increasing the number of splitter plates.
The arc must be transferred from the contacts, guided through the arc runners, driven into the splitter plate assembly, and prevented from establishing alternative paths behind the splitter plates.
The study demonstrates that the material and position of the innermost barrier plate can have a significant influence on this process.
In the reported experiment, an insulating barrier plate positioned close to the top of the splitter plate produced a higher arc-voltage peak and reduced evidence of arc burning behind the splitter plate.
For ACB arc chute development, the key principle is:
Effective arc interruption is not only about splitting the arc—it is about controlling where the arc moves before, during, and after splitting.
Niu Chunping, Ding Juwen, Wu Yi, Yang Fei, Dong Delong, Fan Xingyu, Rong Mingzhe.
Simulation and Experimental Analysis of Arc Motion Characteristics in Air Circuit Breaker.
Plasma Science and Technology, Vol. 18, No. 3, March 2016.
DOI: 10.1088/1009-0630/18/3/05
