Glossary

A

  • AC

    CBE performance specifications assume conventional sinusoidal wave forms, for alternative requirements it is recommended that selection advice is requested.

  • Altitude

    The height above sea level at which the CBE is installed. For operation at altitudes higher than 2000 M, it may be necessary to take into account the dielectric strength of the CBE and the cooling eff ect of the air.

  • Ambient air temperature

    The temperature, determined under prescribed conditions, of the air surrounding the complete CBE (e.g. for an enclosed CBE, it is the air outside the enclosure).

  • Approval authorities

    Internationally accredited agencies competent to test CBE devices to recognized national and/or international standards.

  • Automatic reset circuit breaker

    An automatic reset circuit breaker (cycling circuit breaker) which automatically resets itself and cycles on and off  under persistent fault conditions. Intended for applications where manual supervision is not possible, caution must be exercised when using/ specifying such devices to ensure that safety hazards are not introduced. Equipment that initially stops during an overload condition and then automatically restarts presents obvious dangers. Since cycling times may be faster than the cooling time of the equipment to be protected, a grad-ual heat build up is possible which may permanently damage equipment and create safety risks. Circuit breakers of this type are not classifi ed as CBEs.

  • Auxiliary circuit

    All the conductive parts of a CBE intended to be included in a circuit other than the main circuit and the control circuit of the CBE. I.e. a circuit within a CBE electrically separate from the main and (if fitted) control circuit(s).

  • Auxiliary contacts

    A contact included in an auxiliary circuit and mechanically operated by the CBE.

B

  • Base/surface mounting

    A CBE intended to be mounted, usually by means of a tool (i.e. typically bolt or screw fastened) to a flush surface, either directly or onto an intermediate base.

  • Bimetal, disc type

    A bimetal of small cross-sectional area, usually stamped from a strip, and mechanically formed to provide the bimetal with “snap” characteristics which are evident upon heating.

  • Bimetal, strip type

    A bimetal of larger cross-sectional area than a disc type, the deflection rate of which is in proportion to temperature, usually overcurrent generated in the case of a CBE.

  • Bimetal

    Two dissimilar metals with different coefficients of expansion bonded together such that the bimetal deflects on heating, typically through overcurrent in the case of a CBE application, to directly or indirectly cause the contacts to open.

  • Bus Bar

    Current-carrying conductor, usually rigid, used in an electrical distribution system as a common feed and/or common return.

C

  • Calibration - CBE

    Individual adjustment of a CBE mechanism to ensure its time/current tripping performance complies with published data.

  • Cascade circuit

    A series arrangement of more than one CBE connected between the power source and the load. Especially suited to higher voltage DC circuits to minimize the effects of arcing.

  • Catastrophic fault

    An unintended situation (for example short circuit) which results in an overcurrent likely to cause rapid and irreversible damage to equipment, or components and conductors thereof.

  • CBE (circuit breaker for equipment)

    A mechanical switching device, specifically designed for the protection of equipment, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and automatically breaking currents under specified abnormal circuit conditions. IEC 60934 covers CBEs which are either intended for automatic interruption and non-automatic resetting only, or intended also for performing manual switching operations.

  • Changeover contacts

    A moving contact which together with a fi xed contact provides a pair of closed contacts when the CBE is in the ON position and which is operated by the CBE to provide a pair of closed contacts together with an alternative fi xed contact when the CBE is in the OFF position.

  • Clearance

    The shortest distance in air between two conductive parts.

  • Closed position

    The position in which the predetermined continuity of the main circuit of the CBE is secured i.e. when the CBE actuator is in the ON position the main contact will be closed.

  • Contact(s)

    Circuits within a CBE are opened/closed by at least one pair of contacts - one fi xed, one moving - which may be formed metal parts or purpose-designed contacts according to their intended duty.

  • Control circuit

    A circuit (other than a path of the main circuit) intended for the closing operation or opening operation, or both, of the CBE.

  • Control contacts

    A contact included in a control circuit of a CBE and mechanically operated by the CBE.

  • Cost of ownership

    The true cost of a CBE including the costs of initial acquisition, installation and use calculated over the life cycle of the equipment into which it is fi tted. The cost of replacing a CBE which fails prematurely for reasons of design or workmanship should be allowed for.  (The pain of in-service quality problems continues long after the pleasure of a low cost purchase has passed).

  • Cycling trip-free

    A CBE, the moving contact(s) of which return to the open position when the automatic opening operation is initiated after the initiation of the closing operation, and which will then re-close repeatedly and momentarily, whilst the closing command is maintained. I.e. upon overcurrent the CBE mechanism will cycle to open and close the con-tact(s) repeatedly if the actuator is maintained in the ON position.

D

  • DC (Direct Current)

    From a battery source or full wave rectified.  For alternative requirements it is recommended that selection advice is requested.

  • DIN Rail mounting

    A CBE intended for mounting on a DIN rail, normally to an international standard.  Some CBE models feature a combi-foot design which facilitates their mounting on rails of several different designs.

  • Dual control

    A CBE combining two electrically separate sensing elements. To facilitate, for example, overcurrent protection and voltage operated disconnection by means of an external sensor.

E

  • Electronic hybrid (EH) tripping mode

    Electronic Hybrid CBEs combine solid state overcurrent sensing with the reliability of electromechanical  physical circuit interruption. Typically overcurrents will be electronically limited to a safe level while an electro-mechanical CBE physically disconnects the circuit.

  • Exposed conductive part

    A conductive part which can be readily touched and which is not normally live but which may become live under fault conditions.

F

  • Fault current

    A current resulting from a fault.

  • Fault

    A circuit condition in which current fl ows through an abnormal or unintended path. This may result from an insulation failure or the bridging of insulation. Conventionally the impedance between live conductors or between live conductors and exposed or extraneous conductive parts at the fault position is considered negligible.

  • Full feature

    A CBE with a latching type positively trip-free mechanism, self-cleaning contacts, capable of providing safe and reliable operation for a wide range of commercial, industrial and professional applications.

H

  • High performance CBE

    A CBE of robust design and construction - typically featuring special contacts, a housing resistant to high arcing temperatures and a heavy duty mechanism - providing a high level of resistance to the effects of shock, vibration, salt spray, humidity and similar influences.

  • Hot wire

    A hot wire CBE mechanism features a stretched length of conductive material of small cross-sectional area connected to the trip mechanism. Upon heating through overcurrent, this “wire” will expand causing the contacts to open. This CBE type typically exhibits very fast switching characteristics.

  • Hydraulic magnetic (HM) tripping mode

    CBEs which are operated by a solenoid, the plunger of which moves upon overcurrent to release a latching mechanism causing the contacts to open. Hydraulic fluid damping is employed to introduce deliberate and defi nable delays, depending upon design and the viscosity of the fl uid used, thereby providing a versatile selection of characteristics for many diff erent types of application.

I

  • Integral mounting

    A CBE which is kept in place by fixation means and does not require any other mounting means. i.e. a CBE which may be held within a molded receptacle, for example.

  • Interrupting capacity (rupture capacity)

    The current which a CBE will switch under overcurrent conditions without damage to itself. CBE performance specifi cations will often show fi gures for maximum and normal interrupting capacity; the current values which the CBE will survive for a minimum of three switching cycles and fifty switching cycles respectively. See also rated conditional short circuit.

M

  • Magnetic (MO) tripping mode

    Magnetic solenoid operated CBEs, similar to hydraulic magnetic types but without a delay. These CBEs provide extremely fast protection once specifi ed overcurrent levels are exceeded. Switch-on surges must be controlled to avoid nuisance operation.

  • Main circuit (of a CBE)

    All the conductive parts of a CBE included in the circuit which it is designed to close and open.

  • Main contacts

    A contact included in the main circuit of a CBE, intended to carry, in the closed position, the current of the main circuit.

  • Mains supply

    The electricity supplied by a system connected to the utility distribution grid.

  • Method of operation (R, M, S types)
    • R-type: CBEs for automatic interruption and non-automatic (man-ual resetting only)
    • M-type: CBEs for automatic interruption and non-automatic (manual) resetting, provided with means for manual operation designed for occasional manual switching, but not designed for regular manual switching operations under normal load conditions.
    • S-type: CBEs for automatic interruption and non-automatic (manual) resetting, provided with means for manual operations and designed for regular manual switching operations under normal load conditions
  • Miniature Circuit Breaker (MCB)

    A circuit breaker intended typically for the protection of AC mains supply circuits. This type of circuit breaker is normally physically larger than a CBE, often significantly so.

N

  • Normally closed contacts

    Contacts which are open when the CBE is in the ON position and the main contacts are closed, and which are closed when the main contacts are open.

  • Normally open contacts

    Contacts which are closed when the CBE is in the ON position and the main contacts are closed, and which are open when the main contacts are open.

O

  • Open position

    The position in which the predetermined clearance between open contacts in the main circuit of the CBE is secured.

  • OpenRAN

    OpenRAN (Open Radio Access Networks) is a technology that aims to define open interfaces in communication between networks and cell phones and to map functions in virtualized software.

    For more information on this topic and how E-T-A applies OpenRAN to its products, click here.

  • Operation of a CBE

    The transfer of the moving contact(s) from the open position to the closed position or vice versa. If distinction is necessary, an operation in the electrical sense (for example make or break) is referred to as a switching operation and an operation in the mechanical sense is referred to as a mechanical operation.

  • Overcurrent

    Any current exceeding the rated current of the CBE.

  • Overload current

    An overcurrent occurring in an electrically undamaged circuit.

P

  • PCB mounting

    A CBE with pins for printed circuit board insertion and soldering.

  • Plug-in mounting

    A CBE with terminals designed to be accommodated by a mating receptacle. The CBE can typically be push-fitted into the receptacle and withdrawn as required, without the use of tools.

  • Pole (of a CBE)

    That part of a CBE associated exclusively with one electrically separated conducting path of its main circuit provided with contacts intended to connect and disconnect the main circuit itself and excluding those portions which provide a means for mounting and operating the poles together.

  • Pole, protected

    A pole provided with a means to detect overcurrent, in which event a contact is caused to open.

  • Pole, switched neutral

    A pole, only intended to switch the neutral, and not intended to have a conditional short-circuit capacity.

  • Pole, unprotected

    A pole without any means to detect overcurrent but otherwise generally capable of the same performance of a protected pole of the same CBE.

  • Push-on terminals

    Male terminals designed to accept female connectors, in various sizes, to international standards.

R

  • Rated conditional short-circuit performance

    IEC 60934/EN 60934 defines interrupting capacity as the rated conditional short circuit current performance of a CBE. According to category PC1, this is the value of rated conditional short circuit current (interrupting capacity) for which the prescribed conditions do not include fi tness of the CBE for its further use. PC2 is defined as the value of rated conditional short circuit current for which the prescribed conditions do include fitness of the CBE for its further use.

  • Rated current

    The nominal current that a CBE will carry in uninterrupted duty without tripping, at a specifi ed reference ambient temperature.

  • Rated frequency

    The power frequency for which the CBE is designed and to which the values of the other characteristics correspond.

  • Rated voltage (for a current sensitive CBE)

    The maximum DC and/or AC system voltages up to which the CBE may be safely specified/used. The rated operational voltage of a CBE is the value of voltage to which the performance is referred.

  • Relay trip

    A separate control circuit, electrically isolated from the main circuit of the CBE, the energization of which will cause the main contact(s) to open. Relay trips are available for either voltage sensing or current sensing.

  • Residual current device

    A mechanical switching device or association of devices intended to cause the opening of the contacts when the residual current attains a given value under specified conditions.

  • Residual current

    The vector sums of the instantaneous values of current flowing through all live conductors of a circuit at a point in the electrical installation.

S

  • Screw terminals

    A terminal in which the conductor is clamped under the head of the screw. The clamping pressure may be applied directly by the head of the screw or through an intermediate part, such as a washer, a clamping plate or an anti-spread device.

  • Screw-in panel mounting

    A CBE intended to be fixed to a panel by means of bolts or screws.

  • Self-cleaning contacts

    A moving contact which opens/closes with a mechanical wiping action across the fixed contact. This self-cleaning action helps to minimize contact contamination, there-by keeping resistance low and extending contact life.

  • Short circuit current

    An overcurrent resulting from a fault of negligible impedance between two points intended to be at diff erent potentials in normal service.

  • Shunt circuit (of a CBE)

    An unprotected circuit tap switched through the main contacts of the CBE.

  • Snap-in panel mounting

    A CBE intended to be push-fitted into a panel mounting aperture. The design of the mounting arrangement is unidirectional, i.e. the CBE can readily be push-fitted into the panel, it is withdrawn only with difficulty.

  • Stud terminals

    A threaded stud onto which conductors or ring connectors are fitted. The clamping pressure may be applied directly by a suitably shaped nut or through an intermediate part such as a wash-er, a clamping plate or an anti-spread device.

  • Supplementary Protector

    In North America CBE type devices are defined as Supplementary Protectors by Underwriters Laboratories (UL) and the Canadian Standards Association (CSA). The relevant standards are UL1077 and C22.2 number 235 respectively. It should be noted that these standards normally reference rated conditional short circuit current performance in accordance with IEC 60934 category PC1.

T

  • Tease-free mechanism

    A mechanism which will not allow the main contact(s) to be intentionally or unintentionally held closed until the set position of the mechanism has been correctly attained: tease-free mechanisms are usually of the snap action type and minimize the risk of contact contamination and welding.

  • Thermal (TO) tripping mode

    CBEs which are operated by a bimetal, hot wire or similar element sensitive to the heating effect of overcurrent. The element will either open the contacts directly or will release a latching mechanism causing the contacts to open.

  • Thermal Magnetic (TM) tripping mode

    Thermal magnetic CBEs include a solenoid in series with a thermal ele-ment to provide a more rapid response to higher value overcurrents.  For overcurrents in excess of a predetermined value the solenoid operates and causes the contacts to open.

  • Threadneck panel mounting

    A CBE fitted with a threaded mounting bush intended for insertion through a panel aperture and secured by means of fixing nuts.

  • Trip Free Mechanism

    E-T-A circuit breakers cannot be held closed against an overload. This is achieved through the use of positively trip free designs in accordance with IEC 934/EN 60934 (with the exception of models 1410, 1610, 1658 and 808 which are designed for specialised applications).

  • Trip-free

    Also referred to as positively trip-free. A CBE, the moving con-tact(s) of which return to and remain in the open position when the automatic opening operation is initiated after the initiation of the closing operation, even if the closing command is maintained. i. e. upon overcurrent the CBE mechanism will cause the moving contact(s) to open and remain open, even if the actuator is maintained in the ON position.

  • Tripping characteristics

    The time-current characteristic above which the CBE shall trip.

  • Tripping curves

    A graph showing the relationship between overcurrent (normally expressed as a per-centage of rating) and the CBE tripping time. Typically graphs will show a time-current operating zone defined by the minimum and maximum limits of manufacturing tolerance.

  • Tripping time

    The time interval from the instant at which the associated tripping current begins to fl ow in the main circuit to the instant when this current is interrupted (in all poles).

  • Typical life

    The number of mechanical and/or switching operations at defined values of current and voltage which a CBE will perform and be within specified limits.

U

  • Undervoltage/Zero voltage release

    A release which causes a CBE to open, with or without a delay, when the voltage across the terminals of the release falls below a predetermined value.

V

  • Voltage trip

    An intended operation of a CBE, with or without a delay, when a defi ned voltage is applied across the terminals of the complete CBE or a control circuit within the CBE - see relay trip.

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