Circuit Breaker Glossary

By Schneider Electric.

Bare-cable connector: Conducting part of the circuit breaker intended for connection to power circuits. On PowerPact circuit breakers, you can use Schneider Everlink lugs or copper/aluminum lug options that screw to the connection terminals of the circuit breaker.Connectors have one or more holes (single or multiple cable connector) for the ends of bare cables.

Connection terminals: Flat copper surface, linked to the conducting parts of the circuit breaker and to which power connections are made using bars, connectors or lugs.

Spreaders: Set of three (3P device) or four (4P device) flat, conducting parts made of copper. They are screwed to the circuit breaker terminals to increase the pitch between poles.

Breaking capacity: Value of prospective current that a switching device is capable of breaking at a stated voltage under prescribed conditions of use and behavior. Reference is generally made to the ultimate breaking capacity (Icu) and the service breaking capacity (Ics).

Degree of protection (IP) IEC 60529: Defines device protection against the penetration of solid objects and liquids, using two digits specified in standard IEC60259. Each digit corresponds to a level of protection, where 0 indicates no protection.

• First digit (0 to 6): protection against penetration of solid foreign objects. 1 corresponds to protection against objects with a diameter > 50 mm, 6 corresponds to total protection against dust.
• Second digit (0 to 8): protection against penetration of liquids (water). 1corresponds to protection against falling drops of water (condensation), 8corresponds to continuous immersion.

The enclosure of PowerPact circuit breakers provides a minimum of IP40 (protection against objects > 1 mm) and can reach IP56 (protection against dust and powerful water jets) depending on the installation conditions.

Degree of protection against external mechanical impacts (IK): Defines the aptitude of an object to resist mechanical impacts on all sides, resistance being designated by an identifying number set out by the listing standard. Each number corresponds to the impact energy that the object can handle according to a standardized procedure.

Durability: The term “durability” is used in the standards instead of “endurance” to express the expectancy of the number of operating cycles which can be performed by the equipment before repair or replacement of parts. The term “endurance” is used for specifically defined operational performance.

Electrical durability: With respect to its resistance to electrical wear, equipment is characterized by the number of loaded operating cycles, corresponding to the service conditions given in the relevant product standard, which can be made without replacement.

Frame size: “A term designating a group of circuit breakers, the external physical dimensions of which are common to a range of current ratings. Frame size is expressed in amperes corresponding to the highest current rating of the group. Within a frame size, the width may vary according to the number of poles. This definition does not imply dimensional standardization. “PowerPact circuit breakers are available in seven frame sizes covering 125 A, 150 A,250 A, 600 A, 800 A, 1200 A, and 3000 A.

Insulation class: Defines the type of device insulation in terms of earthing and the corresponding safety for the user, in one of three classes.

• Class I. The device is earthed. Any electrical faults, internal or external, or caused by the load, are cleared via the earthing circuit, thus ensuring user safety.
• Class II. The device is not connected to a protective conductor. User safety is ensured by reinforced insulation around the live parts (an insulating case and no contact with live parts, i.e. plastic buttons, molded connections, etc.) or double insulation.
• Class III. The device may be connected only to SELV (safety extra-low voltage) circuits.

The PowerPact circuit breakers are class II devices (front) and may be installed through the door in class II switchboards (standards IEC 61140 and IEC 60664-1), without reducing insulation, even with a rotary handle or motor mechanism module.

Making capacity: Value of prospective making current that a switching device is capable of making at a stated voltage under prescribed conditions of use and behavior. Reference is generally made to the short-circuit making capacity Icm.

Maximum break time: Maximum time after which breaking is effective, i.e. the contacts separated and the current completely interrupted.

Mechanical durability: With respect to its resistance to mechanical wear, equipment is characterized by the number of no-load operating cycles which can be effected before it becomes necessary to service or replace any mechanical parts.

Non-tripping time:This is the minimum time during which the protective device does not operate in spite of pick-up overrun, if the duration of the overrun does not exceed the corresponding voluntary time delay.

Pollution degree of environment conditions IEC 60947–1:”Conventional number based on the amount of conductive or hygroscopic dust, ionized gas or salt and on the relative humidity and its frequency of occurrence, resulting in hygroscopic absorptionor condensation of moisture leading to reduction in dielectric strength and/or surface resistivity”.

Standard IEC 60947-1 distinguishes four pollution degrees:

• Degree 1. No pollution or only dry, non-conductive pollution occurs.
• Degree 2. Normally, only non-conductive pollution occurs. Occasionally, however,a temporary conductivity caused by condensation may be expected.
• Degree 3. Conductive pollution occurs, or dry, non-conductive pollution occurs which becomes conductive due to condensation.
• Degree 4. The pollution generates persistent conductivity caused, for instance, by conductive dust or by rain or snow.

PowerPact circuit breakers meet degree 3, which corresponds to industrial applications.

Prospective short-circuit current: Current that would flow through the poles if they remained fully closed during the short-circuit.

Rated current (In): This is the current that the device has been certified to carry continuously within all parameters described by the standard.

Rated impulse withstand voltage: “The peak value of an impulse voltage of prescribed form and polarity which the equipment is capable of withstanding without failure under specified conditions of test and to which the values of the clearances are referred. The rated impulse withstand voltage of an equipment shall be equal to or higher than the values stated for the transient over voltages occurring in the circuit in which the equipment is fitted”.

Rated insulation voltage (Vi): “The rated insulation voltage of an equipment is the value of voltage to which dielectric tests and creepage distances are referred. In no case shall the maximum value of the rated operational voltage exceed that of the rated insulation voltage”.

Rated operational current (Ie): “A rated operational current of an equipment is stated by the manufacturer and takes into account the rated operational voltage, the rated frequency, the rated duty, the utilization category and the type of protective enclosure,if appropriate”.

Rated operational voltage (Ve): “A value of voltage which, combined with a rated operational current, determines the application of the equipment and to which the relevant tests and the utilization categories are referred. For multi-pole equipment, it is generally stated as the voltage between phases”. This is the maximum continuous voltage at which the equipment may be used.

Rated short-time withstand current (Icw): “Value of short-time withstand current,assigned to the equipment by the manufacturer, that the equipment can carry without damage, under the test conditions specified in the relevant product standard”. Generally expressed in kA for 0.5, 1 or 3 seconds. This is an essential characteristic for air circuit breakers. It is not significant for molded-case circuit breakers for which the design targets fast opening and high limiting capacity.

Service breaking capacity (Ics): Expressed as a percentage of Icu, it provides an indication on the robustness of the device under severe conditions. It is confirmed by a test with one opening and one closing/opening at Ics, followed by a check that the device operates correctly at its rated current, i.e. 50 cycles at In, where temperature rise remains within tolerances and the protection system suffers no damage.Short-circuit making capacity (Icm):Value indicating the capacity of the device to make and carry a high current without repulsion of the contacts. It is expressed in kA peak.

Suitability for isolation:This capability means that the circuit breaker meets the conditions below.

• In the open position, it must withstand, without flashover between the upstream and downstream contacts, the impulse voltage specified by the standard as a function of the Uimp indicated on the device.
• It must indicate contact position by one or more of the following systems:
  • position of the operating handle
  • separate mechanical indicator
  • visible break of the moving contacts
• Leakage current between each pole, with the contacts open, at a test voltage of 1.1 x the rated operating voltage, must not exceed:
  • 0.5 mA per pole for new devices
  • 2 mA per pole for devices already subjected to normal switching operations
  • 6 mA, the maximum value that must never be exceeded.
• It must not be possible to install padlocks unless the contacts are open. Locking in the closed position is permissible for special applications. PowerPact complies with this requirement by positive contact indication.

Suitable for isolation with positive contact indication: Suitability for isolation is defined here by the mechanical reliability of the position indicator of the operating mechanism, where:

• the isolation position corresponds to the O (OFF) position
• the operating handle cannot indicate the “OFF” position unless the contacts are effectively open.

The other conditions for isolation must all be fulfilled:

• locking in the open position is possible only if the contacts are effectively open
• leakage currents are below the standardized limits
• overvoltage impulse withstand between upstream and downstream connections.

Ultimate breaking capacity (Icu): Expressed in kA, it indicates the maximum breaking capacity of the circuit breaker. It is confirmed by a test with one opening and one closing/opening at Icu, followed by a check that the circuit is properly isolated. This test ensures user safety.

CNOMO machine-tool rotary handle: Handle used for machine-tool control enclosures and providing IP54 and IK08.

Direct rotary handle : This is an optional control handle for the circuit breaker. It has the same three positions I (ON), O (OFF) and TRIPPED as the toggle control. It provides IP40, IK07 and the possibility, due to its extended travel, of using early-make and early break contacts. It maintains suitability for isolation and offers optional locking using a padlock.

Emergency off: In a circuit equipped with a circuit breaker, this function is carried out by an opening mechanism using an MN undervoltage release or an MX shunt trip in conjunction with an emergency off button.

Extended rotary handle: Rotary handle with an extended shaft to control devices installed at the rear of switchboards or control panels. It has the same characteristics as direct rotary handles. It offers multiple locking possibilities using a padlock or a door interlock.

Side rotary handle: Rotary handle with a side shaft to control devices installed in the switchboards. It has the same characteristics as direct rotary handles. It offers multiple locking possibilities using a padlock.

Failsafe remote tripping: Remote tripping is carried out by an opening mechanism using an MN undervoltage release in conjunction with an emergency off button. If power is lost, the protection device opens the circuit breaker.

Cascading /Series Ratings: Cascading implements the current-limiting capacity of a circuit breaker, making it possible to install downstream circuit breakers with lower performance levels.The upstream circuit breaker reduces any high short-circuit currents. This makes it possible to install downstream circuit breakers with breaking capacities less than the prospective short-circuit current at their point of installation.The main advantage of cascading is to reduce the overall cost of electrical distribution equipment.Because the current is limited throughout the circuit downstream of the limiting circuit breaker, cascading applies to all the devices located downstream.

Current discrimination/Selective coordination: Discrimination based on the difference between the current-protection settings of the circuit breakers. The difference in settings between two successive circuit breakers in a circuit must be sufficient to allow the downstream breaker to clear the fault before the up stream breaker trips.

Discrimination: Discrimination is ensured between upstream and downstream circuit breakers if, when a fault occurs, only the circuit breaker placed immediately upstream of the fault trips. Discrimination is the key to ensuring the continuity of service of an installation.

Energy discrimination: This function is specific to PowerPact circuit breakers and supplements the other types of discrimination.

Partial discrimination: The ultimate short-circuit current Icu, but only up to a lesser value. This value is called the discrimination limit. If a fault exceeds the discrimination limit, both circuit breakers trip.

Time discrimination: Discrimination based on the difference between the time-delay settings of the circuit breakers. The upstream trip unit is delayed to provide the downstream breaker the time required to clear the fault.

Total discrimination: Total discrimination is ensured between upstream and downstream circuit breakers if, for all fault values, from overloads up to solid short-circuits, only the downstream circuit breaker trips and the upstream circuit breaker remains closed.

EMC (Electromagnetic compatibility): EMC is the capacity of a device not to disturb its environment during operation (emitted electromagnetic disturbances) and to operate in a disturbed environment (electromagnetic disturbances affecting the device). The standards define various classes for the types of disturbances. Micrologic™ trip units comply with annexes F and J in standard IEC IE60947-2.

Power loss (Pole resistance): The flow of current through the circuit breaker poles produces Joule-effect losses caused by the resistance of the poles.

LCA: Life-cycle assessment ISO 14040: An assessment on the impact of the construction and use of a product on the environment, in compliance with standard ISO 14040, Environmental management, life-cycle assessment (LCA), principles and framework . For PowerPact, this assessment is carried out using the standardized EIME (Environmental Impact and Management Explorer) software, which makes possible comparisons between the products of different manufacturers.It includes all stages, i.e. manufacture, distribution, use and end of life, with set usage assumptions:

• use over 20 years at a percent load of 80 % for 14 hours per day and 20 % for ten hours
• according to the European electrical-energy model.

It provides the information presented below.

• Materials making up the product: composition and proportions, with a check to make sure no substances forbidden by the RoHS directive are included.
• Manufacture: on Schneider Electric production sites that have set up an environmental management system certified ISO 14001.
• Distribution: packaging in compliance with the 94/62/EC packaging directive(optimised volumes and weights) and optimised distribution flows via local centers.
• Use: no aspects requiring special precautions for use. Power lost through Joule effect in Watts must be < 0.02 % of total power flowing through the circuit breaker. Based on the above assumptions, annual consumption from 95 to 200kWh.
• End of life: products dismantled or crushed. For PowerPact circuit breakers, 81 %of materials can be recycled using standard recycling techniques. Less than 2 %of total weight requires special recycling.

RoHS directive (Restriction of Hazardous substances): \European directive 2002/95/EC dated 27 January 2003 aimed at reducing or eliminating the use of hazardous substances. The manufacturer must attest to compliance, without third-party certification. Circuit breakers are not included in the list of concerned products, which are essentially consumer products. That not withstanding, Schneider Electric decided to comply with the RoHS directive. PowerPact products are designed in compliance with RoHS and do not contain (above the authorized levels) lead, mercury, cadmium, hexavalent chromium or flame retardants (polybrominated biphenyls PBB and polybrominated diphenyl ether PBDE).

Safety clearances: When installing a circuit breaker, minimum distances (safety clearances) must be maintained between the device and panels, bars and other protection systems installed nearby. These distances, which depend on the ultimate breaking capacity, are defined by tests carried out in accordance with standard IEC60947- 2.

Temperature derating: An ambient temperature varying significantly from 40°C can modify operation of magnetic or thermal-magnetic protection functions. It does not
affect electronic trip units. However, when electronic trip units are used in high-temperature situations, it is necessary to check the settings to ensure that only the permissible current for the given ambient temperature is let through.

Vibration withstand IEC 60068-2-6: Circuit breakers are tested in compliance with standard IEC 60068-2-6 for the levels required by merchant-marine inspection organizations (Veritas, Lloyd’s, etc.).

WEEE directive (Waste of Electrical and Electronic Equipment): European directive on managing the waste of electrical and electronic equipment. Circuit breakers are not included in the list of concerned products. However, PowerPact products respect the WEEE directive.

Overvoltage category (OVC – Overvoltage category) IEC 60947-1. Annex H: Standard IEC 60664-1 stipulates that it is up to the user to select a measurement device with a sufficient overvoltage category, depending on the network voltage and the transient overvoltages likely to occur. Four overvoltage categories define the field of use for a device.

• Cat. I. Devices supplied by a SELV isolating transformer or a battery.
• Cat. II. Residential distribution, handheld or laboratory tools and devices connected to standardised 2P + earth electrical outlets (230 V).
• Cat. III. Industrial distribution, fixed distribution circuits in buildings (main low voltage switchboards, rising mains, elevators, etc.).
• Cat. IV. Utility substations, overhead lines, certain industrial equipment.

Instantaneous protection I (Ii): This protection supplements Isd. It provokes instantaneous opening of the device. The pick-up is fixed (built-in). This value is always lower than the contact-repulsion level.

Magnetic protection (Im): Short-circuit protection provided by magnetic trip units (see this term). The pick-up setting may be fixed.

Neutral protection (IN): The neutral is protected because all circuit breaker poles are interrupted. The PowerPact B-frame 4P circuit breaker has fixed 100% protection in the far left pole.

Thermal protection (Ir): Overload protection provided by thermal trip units (see this term) using an inverse time curve (I²t).

Auxiliary contact IEC 60947-1: “Contact included in an auxiliary circuit and mechanically operated by the switching device”.

Break contact IEC 60947-1: “Control or auxiliary contact which is open when the main contacts of the mechanical switching device are closed and closed when they are open”.

Make contact IEC 60947-1: “Control or auxiliary contact which is closed when the main contacts of the mechanical switching device are closed and open when they are open”.

Relay (electrical) IEC 60947-1 : “Device designed to produce sudden, predetermined changes in one or more electrical output circuits when certain conditions are fulfilled in the electrical input circuits controlling the device”.

Circuit breaker IEC 60947-2: “Mechanical switching device, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of short circuit”. Circuit breakers are the device of choice for protection against overloads and short-circuits. Circuit breakers may, as is the case for PowerPact, be suitable for isolation.

Circuit breaker utilization category IEC 60947-2: The standard defines two utilization categories, A and B, depending on circuit breaker discrimination with upstream breakers under short-circuit conditions.

• Category A. Circuit breakers not specifically designed for discrimination applications.
• Category B. Circuit breakers specifically designed for discrimination, which requires a short time-delay (which may be adjustable) and a rated short-time withstand current in compliance with the standard.

PowerPact 125 to 600 A circuit breakers are category A, however, by design, they provide discrimination with downstream devices (see the Complementary technical information guide).

Contactor IEC 60947-1: “Mechanical switching device having only one position of rest, operated otherwise than by hand, capable of making, carrying and breaking currents under normal circuit conditions including operating overload conditions”. A contactor is provided for frequent opening and closing of circuits under load or slight overload conditions. It must be combined and coordinated with a protective device against overloads and short-circuits, such as a circuit breaker.

Contactor utilization categories IEC 60947-4-1: The standard defines four utilization categories, AC1, AC2, AC3 and AC4 depending on the load and the control functions provided by the contactor. The class depends on the current, voltage and power factor,as well as contactor withstand capacity in terms of frequency of operation and endurance.

Current-limiting circuit breaker IEC 60947-2: “A Circuit breaker with a break-time short enough to prevent the short-circuit current reaching its otherwise attainable peak value”.

Disconnector IEC 60947-3: “Mechanical switching device which, in the open position, complies with the requirements specified for the isolating function”. A disconnector serves to isolate upstream and downstream circuits. It is used to open or close circuits under no-load conditions or with a negligible current level. It can carry the rated circuit current and, for a specified time, the short-circuit current.

Magnetic release: Release actuated by a coil or a lever. A major increase in the current (e.g. a short circuit) produces in the coil or the lever a change in the magnetic field that moves a core. This trips the circuit breaker operating mechanism. Action is instantaneous. The pick-up setting may be adjustable.

Reflex tripping: PowerPact circuit breakers have a patented reflex-tripping system based on the energy of the arc and that is independent of the other protection functions. It operates extremely fast, before the other protection functions. It is an additional safety function that operates before the others in the event of a very high short circuit.

Release IEC 60947-1: Device, mechanically connected to a mechanical switching device (e.g. a circuit breaker), which releases the holding means and permits the opening or the closing of the switching device. For circuit breakers, releases are often integrated in a trip unit.

Shunt trip (MX): When the shunt trip (MX) receives a pulse-type or maintained voltage within specified tolerances it signals the circuit breaker to open.

Thermal-magnetic trip unit: Trip unit combining thermal protection for overloads and magnetic protection.

Thermal release: Release in which a bimetal strip is heated by the Joule effect. Above a temperature-rise threshold that is a function of the current and its duration (I²t curve= constant, which is representative of temperature rise in cables), the bimetal strip bends and releases the circuit breaker opening mechanism. The pick-up setting maybe adjustable.

Undervoltage release (MN): This type of release operates when the supply voltage drops below the set minimum.