Hubbry Logo
Arc suppressionArc suppressionMain
Open search
Arc suppression
Community hub
Arc suppression
logo
7 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Arc suppression
Arc suppression
Arc suppression
View on Wikipedia
from Wikipedia

Arc suppression is the reduction of the electric arc[1][2][3][4][5] energy that occurs when current-carrying contacts are opened and closed. An electric arc is a man-made, continuous arc-discharge consisting of highly energized electrons and ions supported by an electric current of at least 100mA; not to be confused with an electric spark.[6]

Overview

[edit]

Every time an electrical power device (for example: heaters, lamps, motors, transformers or similar power loads) turns on or off, its switch, relay or contactor transitions either from a CLOSED to an OPEN state ("BREAK") or from an OPEN to a CLOSED state ("MAKE"), under load, an electrical arc occurs between the two contact points (electrodes) of the switch.

There are two distinct forms of electronic contact arcing, each defined by its respective arc initiation mechanism (note that arc initiation is not the same as plasma ignition; i.e., arcs initiate before their plasmas ignite). The two types of contact arc initiation mechanisms are: 1. The Thermionic-Emission-Initiated-Arc (T-Arc) is born out of Current and initiates around V(T-Arc_init_min), and the T-Arc plasma is maintained at or above the minimum-arc-current of I(arc_plasma_min). 2. The Electron Field-Emission-Initiated-Arc (F-Arc) is born out of Voltage and initiates around V(F-Arc_init_min), and the F-Arc plasma is maintained at or above the minimum-arc-current of I(arc_plasma_min). Both T-Arcs and F-Arcs require the combination of a minimum arc-initiation-voltage and a minimum arc-plasma-supporting-current of 300mA to 1000mA. We refer to these current and voltage combinations as the respective T-Arc Domain and F-Arc Domain.
The Domains of Existence for Thermionic-Emission-Initiated Arcs ("T-Arcs") and Electron-Field-Emission-Initiated-Arcs ("F-Arcs")

The temperature of the resulting electric arc is very high (tens of thousands of degrees), causing the metal on the contact surfaces to melt, pool and migrate with the current. The high temperature of the arc causes dissociation of the surrounding gas molecules creating ozone, carbon monoxide, and other compounds. The arc energy slowly destroys the contact metal, causing some material to escape into the air as fine particulate matter. This very activity causes the material in the contacts to degrade quickly, resulting in device failure.[4][7]

Understanding arc suppression requires an understanding of both arcing and arc initiation mechanisms. Contact arcs are either a Thermionic-Emission-Initiated-Arc ("T-Arc") or a Field-Emissions-Initiated-Arc ("F-Arc"), and are maintained by a continuous supply of power (think of an arc welder or a Xenon arc lamp).:

  1. The T-Arc is born out of Current and initiates around V(T-Arc_init_min), and the T-Arc plasma is maintained at or above the minimum-arc-current of I(arc_plasma_min).[8]
  2. The F-Arc is born out of Voltage and initiates around V(F-Arc_init_min), and the F-Arc plasma is maintained at or above the minimum-arc-current of I(arc_plasma_min).[8]

While arcing occurs during both the BREAK and MAKE transitions, the break arc is typically more energetic and thus more destructive.[8][9][10]

Potential MAKE F-Arc plasma extinguishes with the initial MAKE contact impact, followed by a series of MAKE-bounce-T-Arcs.

Arcing initiated during contact MAKE

[edit]

During contact MAKE, F-Arc initiation occurs as the moving electrode nears the stationary electrode. Then the MAKE F-Arc plasma ignites and is promptly extinguished at the instant of contact impact. This initial impact results in a series of plasma pressure amplified MAKE bounces, with each bounce yielding a T-Arc. These bounces continue until the contact is micro-welded in the CLOSED position. (Note that "arc suppression" does not mean "arc elimination", as some tiny arcs ("arclets") yield beneficial micro-welds. These micro-welds are a desired and important power contact feature as they ensure vibration-resistant, low ohmic, and non-permanent electrode connections.)[8][9][10]

The "BREAK Arc" consists of an initial BREAK T-Arc, and is then extended by from one to possibly thousands of BREAK F-Arcs until the contact comes to rest in the OPEN state.

Arcing initiated during contact BREAK

[edit]

The "BREAK Arc" consists of an initial BREAK T-Arc that may be extended by a series of BREAK F-arcs. The initial BREAK T-Arc is created after the explosion of the super-heated molten-metal bridge that had been carrying current as the contact begins to open. As the BREAK T-Arc plasma extinguishes and current is interrupted, inductance in the loop extends the duration of the "BREAK Arc" by initiating a series of BREAK F-Arcs which continue until the contact gap widens beyond the thermodynamic ability to support the burning plasma.[8][9][10]

Uses

[edit]

There are several possible areas of use of arc suppression methods, among them metal film deposition and sputtering, electrostatic processes where electrical arcs are not desired (such as powder painting, air purification, and contact current arc suppression. In industrial, military and consumer electronic design, the latter method generally applies to devices such as electromechanical power switches, relays and contactors. In this context, arc suppression is contact protection.

Contact protection

[edit]
Physical effects of contact arcing - from left to right: pristine unused contact; failed contact after < 100 k unsuppressed cycles (i.e., typical use); used contact in excellent shape after 100 k suppressed cycles; used contact still in excellent shape after 1 million suppressed cycles (a 10x improvement).

Contact protection methods are designed to mitigate the wear and degradation occurring during the intended use of contacts within an electromechanical switch, relay or contactor and thus avoid an excessive increase in contact resistance or premature switch failure.

Arc suppression is an area of interest in engineering due to the destructive effects of the electrical arc to electromechanical power switches, relays and contactors' points of contact.[11] There are many forms of "arc suppression" that provide contact protection in applications operating at less than 1 Ampere. Most of these, however, are more accurately considered "transient suppression" and are therefore ineffective for either arc suppression or contact protection.[12][13]

Effectiveness

[edit]
Screen captures from an oscilloscope measuring the arc energy: current shown by blue line (sinusoidal wave), 2V/div = 5A/div; voltage shown by red line,10V/div.
(left) Unsuppressed AC power electrical arc
(right) An identical arc with suppression.

The efficacy of an arc suppression solution for contact protection can be assessed using the Contact Arc Suppression Factor ("CASF")[14][15] to compare the calculated arc energy of the unsuppressed arc with that of the suppressed arc:

CASF = W(arc) / W(arclet)

Where W(arc) = Unsuppressed arc energy and W(arclet) = Suppressed arc energy. The unsuppressed and suppressed arc energy must be obtained graphically from oscilloscope measurements. The unsuppressed and suppressed arc energy is expressed in Watt seconds [Ws] or Joules [J]. The resulting Contact Arc Suppression Factor [CASF] is dimensionless.

Contact Arc Suppression Factor (CASF) test set-up. The results obtained using this test set-up allow for determining the effectiveness of a contact arc suppression on either an electromechanical relay or a contactor.

W(arc) = V(arc) × I(arc) × T(arc)

Where V(arc): Arc burn voltage, I(arc): Arc burn current, is approximately I(load), where I(load) may be in the range from a few Ampere [A] to kilo Ampere [kA]; and T(arc): Arc burn duration, can be on the order of microseconds [μs] to seconds [s].

W(arclet) = V(arclet) × I(arclet) × T(arclet)

Where V(arclet): Arc ignition voltage, depending on the contact metal. E.g. about 12V for silver indium tin oxide; I(arclet): Arclet current, is approximately I(load) and may be in the range from a few Ampere [A] to kilo Ampere [kA]; and T(arclet): Arclet burn duration, is on the order of a few microseconds [μs].

Electrical arcing across the contacts of an electromechanical relay may be effectively measured using an oscilloscope connected to a differential voltage probe across the relay contacts and a high speed current probe to measure the current through the contacts during operation under load.[14][15]

Alternatively, the electrical arc may also be visually observed on an electromechanical power switch, relay and contactor, with visible contacts, while the contacts are opening and closing under load.

Common devices

[edit]

Common devices that may be reasonably effective arc suppressors in applications operating below 2 Amperes include capacitors, snubbers, diodes, Zener diodes, varistors, and transient voltage suppressors.[12][16][17] Contact arc suppression solutions that are considered effective in applications operating at more than 2 Amperes include:

  1. Electronic Power Contact Arc Suppressor
  2. Solid state relays are not electromechanical, have no contacts, and, thus, do not create electrical arcs.[18]
  3. Hybrid power relays
  4. Hybrid power contactors

Specialized devices

[edit]
An electronic power contact arc suppressor attached in parallel across the contact of a relay or contactor (Fig. 1 of issued patent U.S. 8,619,395 B2)

The circuit diagram is part of an issued patent for an electronic power contact arc suppressor intended to protect the contacts of electrical relays or contactors. It suppresses arcs by providing an alternate path around contacts as they open or close. [19][20]

Some contact arc suppressors operate connected solely across the protected contact, while other contact arc suppressors are also connected to the coil of the contactor to provide the suppressor with additional input about contact operation.

Benefits of arc suppression

[edit]

Arc suppression techniques can produce a number of benefits:[20]

  1. Minimized contact damage from arcing and therefore reduced maintenance, repair and replacement frequency.
  2. Increased contact reliability.
  3. Reduced heat generation resulting in less heat management measures such as venting and fans.
  4. Reduced ozone and pollutant emissions.
  5. Reduced electromagnetic interference (EMI) from arcs - a common source of radiated EMI.

See also

[edit]

References

[edit]

Further reading

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Arc suppression

View on Grokipedia
from Grokipedia
Arc suppression is a set of techniques designed to minimize or extinguish luminous plasma discharges known as electric arcs, which form when current-carrying contacts separate or during fault conditions in power systems, thereby preventing contact erosion, equipment damage, and safety risks. These arcs arise from the rapid interruption of current, particularly in inductive loads where stored energy generates high-voltage transients, or in capacitive systems during ground faults. In low-voltage applications such as relays, solenoids, and switches, arc suppression protects contacts by absorbing or diverting inductive kickback energy; common methods include flyback diodes placed in parallel with DC loads to provide a path for reverse current, RC snubber networks (-capacitor pairs) connected across contacts or loads to limit voltage rise rates, and metal-oxide varistors (MOVs) or bidirectional transient voltage suppressor (TVS) diodes for AC circuits that clamp transients above a . For DC inductive suppression, diodes extend contact life by shunting energy, while RC networks with values of 0.5–3 times the peak voltage divided by switch current and capacitors starting at 0.1 μF reduce arcing in both AC and DC setups. MOVs and TVS diodes, with lower in the latter, conduct excess energy during spikes, preventing restriking arcs that can multiply the original inductive energy several times. In high-voltage power distribution networks, arc suppression primarily involves Petersen coils (arc suppression reactors or earth fault neutralizers), single-phase inductive devices connected between the neutral point of transformers and ground to compensate for system capacitance during single-line-to-ground faults. These coils, invented by Waldemar Petersen in 1917 and typically oil-immersed with adjustable reactance ratios up to 10:1, reduce fault currents to 5–10 A or less, allowing the arc to self-extinguish without service interruption and avoiding damage to conductors or insulators. The reactor's inductance is tuned to match the network's earth capacitance (e.g., 0.1–0.7 μF/km for cables), creating an opposing inductive current that neutralizes the capacitive fault current. Overall, arc suppression enhances system reliability and safety across applications, from industrial automation where zero-crossing switching in solid-state devices like SCRs minimizes inductive energy release, to utility-scale protection against fires and outages. Without proper suppression, repetitive arcing can drastically shorten component life and pose severe hazards, underscoring its role as a critical design consideration in modern electrical systems.

Fundamentals of Electrical Arcs

Arc formation and characteristics

An electrical arc is a self-sustained plasma discharge that forms between two electrodes when the applied voltage exceeds the of the intervening medium, leading to gas and a conductive path for current flow. This process begins with an initial breakdown, where free electrons accelerate under the high , colliding with gas molecules to produce further via an , ultimately creating a plasma column of ionized gas, electrons, and ions. The plasma exhibits high electrical conductivity due to the abundance of free charge carriers, enabling sustained current at relatively low voltages after . Key characteristics of an electrical arc include its extreme , typically ranging from 5,000°C to 20,000°C in the plasma core, which is sufficient to vaporize materials and dissociate surrounding gases. The process maintains the arc's conductivity, with densities on the order of 10^15 to 10^18 per cubic centimeter, depending on current levels. dissipation occurs primarily through and as heat, visible and light emission, and manifesting as sound, with the plasma's arising from excited atomic and ionic recombining. These properties make arcs highly erosive to and capable of rapid energy transfer. Electrical arcs can be classified into two primary types based on initiation mechanism: transient arcs, or T-arcs (thermionic-emission-initiated arcs), which form during current interruption when residual heat from the electrodes emits electrons to bridge the gap; and fundamental arcs, or F-arcs (field-emission-initiated arcs), which arise from voltage breakdown across an insulating gap via quantum tunneling of electrons from the . T-arcs are short-lived and dependent on prior thermal conditions, while F-arcs are triggered by high exceeding 10^7 V/m in typical gases like air. The stability and behavior of an electrical arc are influenced by several factors, including electrode material, which affects emission properties and erosion rates—such as tungsten providing higher thermionic emission than copper; gap distance, where narrower gaps lower the initiation voltage but increase arc intensity; surrounding medium, with air supporting arcs at atmospheric pressure while vacuum or inert gases like SF6 alter ionization thresholds and quenching; and current/voltage levels, where higher currents enhance thermal ionization for stability, but excessive voltage can lead to elongation or extinction. Historically, electrical arcs were first systematically observed in the early 19th century by , who in 1807-1808 demonstrated luminous discharges between carbon electrodes using a large battery at the , laying the groundwork for development in the 1810s. , as Davy's assistant, contributed to early electrochemical studies in the 1830s that indirectly advanced understanding of arc-related discharges through his work on and .

Arcs in switching operations

In electrical switching operations, arcs form during both the make and break phases of mechanical contact closure and separation. During the contact make phase, a field-emission-initiated arc (F-arc) occurs as the moving electrode approaches the stationary one, driven by across the narrowing gap exceeding the spark potential of approximately 327 V, leading to dielectric breakdown and plasma formation. Upon initial contact, this F-arc extinguishes, but subsequent contact bounce can initiate short thermionic-emission-initiated arcs (T-arcs) due to localized heating and micro-welding at the contact points, where current flow through tiny asperities generates sufficient thermal energy for emission. During the contact break phase, the process begins with a T-arc as the contacts separate and the molten metal bridge between them ruptures under , sustaining the plasma through thermionic emission from the heated surfaces. This T-arc is often prolonged by subsequent F-arcs, particularly in inductive circuits where stored energy maintains across the widening gap until it exceeds the plasma sustainment distance, typically a few millimeters. Arcs in (AC) systems differ markedly from those in (DC) systems due to the periodic nature of AC voltage. In AC switching, the arc tends to self-extinguish at the current zero-crossing, where the voltage naturally drops to zero, interrupting the plasma column without additional intervention. In contrast, DC arcs persist because the unidirectional voltage and current do not provide a natural zero-crossing, requiring external mechanisms to force interruption and prevent prolonged arcing. These switching arcs lead to several detrimental effects on contacts and surrounding systems. Contact erosion results from the extreme arc temperatures of 6000–20,000 , which vaporize and eject metal material from the electrodes. Pitting occurs due to localized high current densities causing intense, uneven heating and formation on contact surfaces. Material transfer happens as accelerated electrons heat the more than the , leading to preferential deposition and imbalance between contacts. Additionally, arcs generate (EMI) by acting as broadband spark-gap transmitters, emitting noise from 30 MHz to 1 GHz during make and break transitions. The high-temperature plasma dissociates air molecules, producing (O₃), nitrous oxides (NO, NOₓ), and fine particulates from vaporized contact materials, which can escape into the environment in open-air devices. Quantitatively, arc durations in low-voltage switching typically range from 1–10 ms, with AC arcs around 5 ms and DC arcs extending to tens or hundreds of ms depending on load . Energy dissipation varies from millijoules (mJ) in low-power resistive loads to kilojoules (kJ) in high-power inductive or fault scenarios, scaling with current, voltage, and circuit parameters.

Arc Suppression Techniques

Passive suppression methods

Passive suppression methods encompass a range of non-powered techniques that mitigate arc formation and energy in electrical switching by leveraging physical, material, or circuit properties to dissipate, redirect, or cool arc energy. These approaches are particularly effective in low- to medium-voltage applications where inductive kickback or contact separation generates transient voltages and currents that sustain arcs. Unlike active methods, passive techniques operate continuously without external power or control electronics, relying on inherent circuit elements or mechanical designs to limit arc duration and intensity. Snubber circuits, typically consisting of resistor- (RC) networks connected across switch contacts or inductive loads, absorb from voltage transients during switching operations. The charges rapidly to limit the rate of voltage rise (dV/dt) across the contacts, while the dissipates the stored as , parasitic resonances and reducing peak voltages that could initiate or prolong arcs. For optimal performance, the value approximates the of the resonant circuit, L/C\sqrt{L/C}
Add your contribution
Related Hubs
User Avatar
No comments yet.