1. General
1.1 Moulded-Case Circuit Breakers (MCCB) shall comply with IEC 60947-1 and 60947-2 standards or with the corresponding standards applicable in the member countries (VDE 0660, BS 4752, NF EN 60947-1/2) :
− they shall be of category A with a rated service breaking capacity (Ics) equal to the ultimate breaking capacity (Icu) – on all the operational voltage range for the ratings up to 250A, up to 500V for the greater ratings
− they shall have a rated operational voltage of 690 V AC (50/60 Hz),
− they shall have a rated insulation voltage of 800 V AC (50/60 Hz),
− they shall be suitable for isolation, as defined by IEC60947 –1 and -2, §7.1.7 for the overvoltage Category IV for a rated insulation voltage up to 690V according to IEC60664-1.
− they shall be of category A with a rated service breaking capacity (Ics) equal to the ultimate breaking capacity (Icu) – on all the operational voltage range for the ratings up to 250A, up to 500V for the greater ratings
− they shall have a rated operational voltage of 690 V AC (50/60 Hz),
− they shall have a rated insulation voltage of 800 V AC (50/60 Hz),
− they shall be suitable for isolation, as defined by IEC60947 –1 and -2, §7.1.7 for the overvoltage Category IV for a rated insulation voltage up to 690V according to IEC60664-1.
1.2 MCCBs shall be designed according to Eco-design complying with ISO 14062 Especially MCCB’s materials shall be of hallogen free type.
1.3 MCCBs shall be available in fixed or plug-in/withdrawable versions as well as in 3-pole and 4-pole versions. For plug-in/withdrawable versions, a safety trip shall provide advanced opening to prevent connection and disconnection of a closed circuit breaker
1.4 MCCBs shall be designed for both vertical and horizontal mounting, without any adverse effect on electrical performance. It shall be possible to supply power either from the upstream or downstream side.
1.5 MCCBs shall provide class II insulation (according to IEC 60664-1 standard) between the front and internal power circuits
2. Construction, operation, environment
2.1 For maximum safety, the power contacts shall be insulated in an enclosure made of a
thermosetting. material from other functions such as the operating mechanism, the case, the trip unit and auxiliaries
thermosetting. material from other functions such as the operating mechanism, the case, the trip unit and auxiliaries
2.2 All poles shall operate simultaneously for circuit breaker opening, closing and tripping.
2.3 MCCBs shall be actuated by a toggle or handle that clearly indicates the three positions: ON, OFF and TRIPPED.
2.4 In order to ensure suitability for isolation complying with IEC 60947-2 § 7-27: the operating mechanism shall be designed such that the toggle or handle can only be in OFF position (O) if the power contacts are all actually separated, in OFF position, the toggle or handle shall indicate the isolation position. Isolation shall be provided by a double break on the main circuit.
2.5 MCCBs shall be able to receive a device for locking in the “isolated” position, with up to 3 padlocks
2.6 MCCBs shall be equipped with a “push to trip” button in front to test operation and the opening of the poles.
2.7 Auxiliaries and accessories
2.7.1 It shall be possible to equip MCCBs with a motor mechanism for electrically controlled operation. An “auto/manual” switch in front shall, when set to the “manual” position, lock out electrical control; when set to “auto”, lock out the manual control; remote indication of “manual” or “auto” mode shall be possible. It shall also be possible to seal the access to the “auto” control. Closing shall take place in less than 80 ms.
Following tripping due to electrical faults (overload, short-circuit, earth fault), remote reset shall be inhibited.
− It shall however be possible if opening was initiated by a voltage release.
− The operating mechanism shall be of the stored-energy type only
Following tripping due to electrical faults (overload, short-circuit, earth fault), remote reset shall be inhibited.
− It shall however be possible if opening was initiated by a voltage release.
− The operating mechanism shall be of the stored-energy type only
2.7.2 The addition of a motor mechanism or a rotary handle shall in no way affect circuit breaker characteristics:
− only three stable tripping mechanism positions (ON, OFF and TRIPPED) shall be possible with the motor mechanism,
− suitability for isolation shall be provided by positive contact indication (ON and OFF) in front of the motor mechanism module
− only three stable tripping mechanism positions (ON, OFF and TRIPPED) shall be possible with the motor mechanism,
− suitability for isolation shall be provided by positive contact indication (ON and OFF) in front of the motor mechanism module
2.7.3 MCCBs shall be designed to enable safe on-site installation of auxiliaries such as voltage releases (shunt and undervoltage releases) and indication switches as follows:
− they shall be separated from power circuits,
− all electrical auxiliaries shall be of the snap-in type and fitted with terminal blocks,
− all auxiliaries shall be common for the entire range,
− auxiliary function and terminals shall be permanently engraved on the case of the circuit
breaker and the auxiliary itself,
− the addition of auxiliaries shall not increase the volume of the circuit breaker.
− they shall be separated from power circuits,
− all electrical auxiliaries shall be of the snap-in type and fitted with terminal blocks,
− all auxiliaries shall be common for the entire range,
− auxiliary function and terminals shall be permanently engraved on the case of the circuit
breaker and the auxiliary itself,
− the addition of auxiliaries shall not increase the volume of the circuit breaker.
2.7.5 It shall be possible to assemble earth fault protection moulded-case circuit breakers by adding a residual current device (RCD) directly to the circuit breaker case. The resulting device shall: comply with appendix B of IEC 60947-2 standard,
− be immunised against nuisance tripping as per IEC 60255 and IEC 61000-4 standards,
− be capable of working normally down to -25 °C ambient temperature,
− operate without an auxiliary power supply, i.e. it shall be capable of operating normally on any 2-phase or 3-phase power network with a voltage between 200 V and 440 V, and of tripping the circuit-breaker even in the event of voltage dips down to 80 V
− be immunised against nuisance tripping as per IEC 60255 and IEC 61000-4 standards,
− be capable of working normally down to -25 °C ambient temperature,
− operate without an auxiliary power supply, i.e. it shall be capable of operating normally on any 2-phase or 3-phase power network with a voltage between 200 V and 440 V, and of tripping the circuit-breaker even in the event of voltage dips down to 80 V
3. Protection functions
3.1 General recommendations
MCCBs with ratings up to 250 A shall be equipped with fully interchangeable trip units in order to ensure the protection against overcharge and short-circuit. The trip units shall be either of:
− thermal-magnetic
− electronic
MCCBs with ratings over 250 A shall be equipped with electronic trip units.
− thermal-magnetic
− electronic
MCCBs with ratings over 250 A shall be equipped with electronic trip units.
3.2 Common features
3.2.1 Electronic and thermal-magnetic trip units shall be adjustable and it shall be possible to fit lead seals to prevent unauthorised access to the settings
3.2.2 Electronic trip units shall comply with appendix F of IEC 60947-2 standard (measurement of rms current values, electromagnetic compatibility, etc.)
3.2.3 Protection settings shall apply to all circuit breaker poles
3.2.4 The trip units shall not augment overall circuit breaker volume
3.2.5 All electronic components shall withstand temperatures up to 125 °C.
3.3 Thermal-magnetic trip units (up to 250 A)
Characteristics:
− Adjustable thermal protection from 0.7 to 1.0 times the current rating
− Fixed magnetic protection for current ratings up to 200 A
− Adjustable (from 5 to 10 times the current rating) for current ratings greater than 200 A.
− It shall be possible to ensure neutral protection. The tripping threshold shall be equal to that of the phases or to a reduced value (generally half of that of the phases).
3.2.2 Electronic trip units shall comply with appendix F of IEC 60947-2 standard (measurement of rms current values, electromagnetic compatibility, etc.)
3.2.3 Protection settings shall apply to all circuit breaker poles
3.2.4 The trip units shall not augment overall circuit breaker volume
3.2.5 All electronic components shall withstand temperatures up to 125 °C.
3.3 Thermal-magnetic trip units (up to 250 A)
Characteristics:
− Adjustable thermal protection from 0.7 to 1.0 times the current rating
− Fixed magnetic protection for current ratings up to 200 A
− Adjustable (from 5 to 10 times the current rating) for current ratings greater than 200 A.
− It shall be possible to ensure neutral protection. The tripping threshold shall be equal to that of the phases or to a reduced value (generally half of that of the phases).
3.4 Electronic trip units (from 250 A)
3.4.1 Characteristics
Long time protection (LT)
− Selectable Ir threshold settings from 36% to 100 % of the trip unit rating
Short time protection (ST)
− Isd threshold shall be adjustable from 1,5 to 10 times the thermal setting Ir,
− The time delay shall be either adjustable or fixed at 40 ms,
− Instantaneous protection
− The threshold shall be either adjustable or fixed (starting from 1.5 times In and up to a value between 11 and 15 times In, depending on the rating)
3.4.2 Four-pole devices shall be equipped for neutral protection:
Long time protection (LT)
− Selectable Ir threshold settings from 36% to 100 % of the trip unit rating
Short time protection (ST)
− Isd threshold shall be adjustable from 1,5 to 10 times the thermal setting Ir,
− The time delay shall be either adjustable or fixed at 40 ms,
− Instantaneous protection
− The threshold shall be either adjustable or fixed (starting from 1.5 times In and up to a value between 11 and 15 times In, depending on the rating)
3.4.2 Four-pole devices shall be equipped for neutral protection: