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Protecting low-voltage circuits

1-1 Description

1-1 Description

The most common faults occurring with low-voltage circuits 
are overcurrent (resulting from overload or short-circuit), 
ground faults, and phase-loss. A device that will protect 
equipment from these faults is therefore needed for reliable 
and economical operation. The following section describes 
lowvoltage circuit faults along with measures to protect against 
them.

Содержание BW1000RAE

Страница 1: ...DISTRIBUTION Molded Case Circuit Breakers Earth Leakage Circuit Breakers Technical information 62D4 E 0058...

Страница 2: ......

Страница 3: ...nsformers 63 3 7 Welder circuit applications 66 3 8 Selecting an MCCB for capacitor circuit 69 3 9 MCCBs for semiconductor circuit 73 3 10 Protecting SSCs using MCCBs or MMSs 77 3 11 Protecting invert...

Страница 4: ...wider selection of products than ever before Now with superior applicability operability and safety MCCBs have rmly established their place in the world of overcurrent protection devices for low volta...

Страница 5: ...low voltage circuits 1 1 Description 4 1 2 Overcurrent protection 1 2 1 Overcurrent fault 5 1 2 2 Overcurrent protection 5 1 3 Phase loss protection 1 3 1 Phase loss fault 6 1 3 2 Phase loss burnout p...

Страница 6: ...age circuits are overcurrent resulting from overload or short circuit ground faults and phase loss A device that will protect equipment from these faults is therefore needed for reliable and economica...

Страница 7: ...ed current it results in thermal damage A circuit breaker is used to ensure quick tripping to protect the connected devices the breaker having a lower operating characteristic curve than the heating c...

Страница 8: ...an generate enough heat to burn out the windings This can develop eventually into a short circuit or ground fault A phase loss protection device protects the motor windings from burning and prevents t...

Страница 9: ...2 3 Overload switching performance 26 2 4 Performance with current at 100 2 4 1 Temperature rise 27 2 4 2 Internal resistance and power consumption 27 2 5 Durability 2 5 1 Switching durability 29 2 5...

Страница 10: ...ce versa This means that a lower overcurrent makes the bimetal reach the operating temperature as the ambient temperature rises because the bimetal s operating temperature is constant Hydraulicmag net...

Страница 11: ...istic varies depending on the type of trip device as shown in Table 2 3 Table 2 3 Effect of mounting angle on overcurrent trip Trip device Effect of mounting angle Thermalmagnetic Although the heat ra...

Страница 12: ...active force by the high frequency Table 2 5 Operating characteristic changes for DC circuit application Trip device Inverse time delay trip characteristic Instantaneous trip characteristics Operating...

Страница 13: ...r s grid The grid thus splits the arc into a series of shorter arcs With the arc stretched and split up in this way the resistance and the arc voltage increase due to the combined action of cooling by...

Страница 14: ...uation reaches its maximum when M Im R2 ZL 2 Em 2 Fig 2 6 Short circuit current oscillogram 1 2 cycle i A B C X Y P iS P A C B t 0 i iS Short circuit current C C Intermediate line between the envelope...

Страница 15: ...ine side exhaust vent and because this gas is conductive it could induce an interphase short circuit or ground fault if it bridges adjacent bare live parts or a bare live part and an adjacent grounded...

Страница 16: ...AG RAG HAG 40 to 125A BW125JAGU RAGU 40 to 125A EW125JAGU RAGU 40 to 125A BW50HAG 30A EW50HAG 30A BW125JAG RAG HAG 30A EW125JAG RAG HAG 30A BW125JAGU RAGU 30A EW125JAGU RAGU 30A BW50HAG 20A EW50HAG 20...

Страница 17: ...AG HAG 40 to 125A EW125JAG RAG HAG 40 to 125A BW125JAGU RAGU 40 to 125A EW125JAGU RAGU 40 to 125A BW50HAG 30A EW50HAG 30A BW125JAG RAG HAG 30A EW125JAG RAG HAG 30A BW125JAGU RAGU 30A EW125JAGU RAGU 30...

Страница 18: ...G HAG EW800EAG RAG HAG BW400EAG SAG RAG HAG EW400EAG SAG RAG HAG BW250JAG SAG RAG HAG BW160JAG SAG RAG EW250JAG SAG RAG EW160JAG SAG RAG BW50HAG 40 50A BW125JAG SAG RAG HAG 40 to 125A EW125JAG SAG RAG...

Страница 19: ...BW400EAG SAG RAG HAG EW400EAG SAG RAG HAG BW250JAG SAG RAG HAG BW160JAG SAG RAG EW250JAG SAG RAG EW160JAG SAG RAG BW50HAG 40 50A BW125JAG SAG RAG HAG 40 to 125A EW125JAG SAG RAG 40 to 125A BW50HAG 30A...

Страница 20: ...it current the current which would ow if no protection devices were installed the actual peak current limited current thermal stress A2 s i e the energy dissipated by the short circuit in a conductor...

Страница 21: ...4050 70 100 150200 300 2 3 5 2 10 5 3 5 10 6 2 3 5 10 7 2 3 5 10 8 2 1 41 3 5 10 9 A 2 s BX630 BX400 BX250 BX100 BX160 H R H R kA rms 2 3 4 6 10 20 30 4050 70 100 150200 300 2 3 5 2 10 5 3 5 10 6 2 3...

Страница 22: ...ircuit current k peak 2 3 4 6 10 20 30 4050 70 100 200 300 300 200 100 80 70 60 50 40 30 20 10 8 7 6 5 4 kA rms k BX630 H R H R BX400 BX250 BX100 BX160 146 2 3 4 6 10 20 30 40 60 65 100 200 300 300 20...

Страница 23: ...BX250 BX100 BX160 H R R Rated short circuit current kA rms Rated short circuit current kA rms Thermal stress curves Voltage 400 440 V AC 1 Voltage 660 690 V AC Limited energy Limited energy BX800H BX...

Страница 24: ...0 0 30 30 BW63SAG EW63SAG 30 10 40 40 25 15 0 0 0 0 30 30 BW63RAG EW63RAG 50 25 50 50 25 15 0 0 10 5 50 50 BW100AAG EW100AAG 10 20 15 0 0 50 50 BW100EAG EW100EAG 50 25 50 50 25 15 0 0 0 5 50 50 BW125...

Страница 25: ...live bare busbars Minimum clearances for BX100 to 630 Operating voltage Clearances with respect to live bare busbars spacing y 60 mm spacing 60 mm F1 F2 F1 F2 U 440 V 350 350 80 80 440 V d U d 600 V...

Страница 26: ...bars for circuit breaker connections block off the busbars using insulating screens BX800 to 1600 xed devices F 146 5 A A B B An overhead clearance of 50 mm is required to remove the arc chutes Insul...

Страница 27: ...s on the other hand can be reset immediately after tripping It takes the plunger a few minutes to return to its normal position however which means that trip characteristics will not be as speci ed fo...

Страница 28: ...per hour 100 or less Max operating voltage Ue AC 6 times the rated current In 150A min Power factor 0 5 45 to 62Hz 9 Total 12 3 120 More than 100 but 315 or less 120 More than 315 but 630 or less DC...

Страница 29: ...able 7 80K 35K 50K JISC 8201 2 1 JISC 8201 2 2 80K 35K 50K UL 489 Table 40 1 reference 50K 60K 60K UL 60947 4 1 Table 2 3 reference 65K 35K 50K 2 4 2 Internal resistance and power consumption The brea...

Страница 30: ...4 0 9 5 20 11 8 14 2 30 5 0 13 5 40 2 7 13 0 50 2 1 15 8 60 1 5 16 2 75 1 1 18 6 100 0 8 24 0 125 0 7 32 8 BW250EAG BW250JAG BW250RAG BW250HAG 125 0 56 26 3 150 0 49 33 1 160 0 39 30 0 175 0 39 35 8 2...

Страница 31: ...T CLOSE THE CIRCUIT LONG ENOUGH TO ALLOW CURRENT TO REACH maximum levels This must not take longer than 2 seconds however Table 2 12 MCCB switching durability Circuit conditions Rated current A Operat...

Страница 32: ...the durability speci ed by the total number of switching operations both with and without current as given in Table 2 14 Table 2 14 Switching durability of MCCB accessories Accessory actuated by swit...

Страница 33: ...part The breaker should withstand the following voltages above the rated voltage applied to the control circuit for one minute 60V or less 1000V More than 60V but less than 600V Rated voltage u 2 100...

Страница 34: ...25RAG 2P 3P BW125HAG 3P EW125JAG 3P EW125SAG 3P EW125RAG 3P 1 72 1 9 2 45 21 10 11 12 5 33 7 95 0 8 61 3 BW125JAG 4P BW125SAG 4P BW125RAG 4P EW125JAG 4P EW125SAG 4P EW125RAG 4P 2 35 2 6 3 35 21 10 11...

Страница 35: ...ide of transformers 3 6 1 Inrush current for transformer excitation 63 3 6 2 Selecting an MCCB for transformer primary circuit 63 3 6 3 Transformer primary side circuit selection 64 3 7 Welder circuit...

Страница 36: ...OUNTING ANGLE s 4ERMINATION 4 Applications s INE PROTECTION s OTOR PROTECTION s NSTANTANEOUS TRIP s ARINE USE s 3PECIAL PURPOSE 7ELDER CAPACITOR LIGHTS 5 Short circuit breaking capacity s ULLY RATED s...

Страница 37: ...cted equipment types Wires loads Types by use Line protection Motor protection Instantaneous trip type Switching frequency Operating method Remote manual Operation Operating durability Operating devic...

Страница 38: ...protect the cable and equipment from the overcurrent The load current must not exceed the derated current value when the MCCB is derated according to the following environmental factors 1 Effects of...

Страница 39: ...IN THE OVERLOAD REGION s 2ATED SHORT CIRCUIT BREAKING CAPACITY OF THE s AX BREAKING 2 t value at the time of MCCB breaking s REEDOM FROM MALFUNCTIONING CAUSED BY AMBIENT conditions starting character...

Страница 40: ...uit such as a distribution system terminal The operating times must be coordinated between the breakers as a result so they will not track the breaker on the power supply side This is known as selecti...

Страница 41: ...circuit breaker 100 10 1 10 1 0 0 1 0 01 0 001 min sec Operating characteristic of main circuit breaker Operating characteristic of branch circuit breaker Operating time 2 Selective trip coordination...

Страница 42: ...s that coordination is easier at each current level as the time the current is on gets shorter The main breaker must trip at high speed in this case Condition c suggests that coordination is easier wi...

Страница 43: ...32SAG EW32SAG 5 22 50 60 60 10 30 30 30 BW50AAG EW50AAG 2 5 5 10 10 10 5 7 5 7 5 7 5 BW50EAG BW63EAG EW50EAG EW63EAG 5 22 50 60 60 10 30 30 30 BW50SAG BW63SAG EW50SAG EW63SAG 10 22 50 60 60 10 30 30 3...

Страница 44: ...sym 10 30 50 65 18 30 50 65 30 36 50 70 36 50 70 36 50 125 BW32SAG EW32SAG 2 5 10 10 15 15 10 10 10 10 BW50EAG BW63EAG EW50EAG EW63EAG 2 5 10 10 15 15 10 10 10 10 BW50SAG BW63SAG EW50SAG EW63SAG 7 5 1...

Страница 45: ...stics as well See Fig 3 6 Fig 3 6 Selective tripping characteristic MCCB MCCB Ternary trip element MCCB Branch MCCB Branch MCCB Load side Main MCCB Ternary trip element Relay time Current Range with p...

Страница 46: ...1 2 2 0 2 5 4 0 5 5 5 5 5 BW50SAG BW63SAG 10 0 5 1 2 2 0 2 5 4 0 5 8 10 10 10 10 BW125JAG 50 0 5 1 2 2 0 2 5 4 0 5 8 50 50 50 50 BW250JAG 50 2 0 2 5 4 0 5 8 50 50 50 50 BW400SAG 85 4 0 5 8 85 85 85 85...

Страница 47: ...5 0 5 1 2 2 0 2 5 2 5 2 5 2 5 2 5 2 5 2 5 BW50SAG BW63SAG 7 5 0 5 1 2 2 0 2 5 4 0 5 8 7 5 7 5 7 5 7 5 BW125JAG 30 0 5 1 2 2 0 2 5 4 0 5 8 30 30 30 30 BW250JAG 30 2 0 2 5 4 0 5 8 30 30 30 30 BW400SAG 3...

Страница 48: ...0 5 8 25 25 25 25 EW250EAG 36 2 0 2 5 4 0 5 8 36 36 36 36 EW400EAG 50 4 0 5 8 50 50 50 50 EW630EAG 50 5 8 50 50 50 50 EW800EAG 50 50 50 50 50 EW32SAG 5 0 5 1 2 2 0 2 5 4 0 5 5 5 5 5 EW50SAG EW63SAG 1...

Страница 49: ...18 2 0 2 5 4 0 5 8 18 18 18 18 EW400EAG 30 4 0 5 8 30 30 30 30 EW630EAG 36 5 8 36 36 36 36 EW800EAG 36 36 36 36 36 EW32SAG 2 5 0 5 1 2 2 0 2 5 2 5 2 5 2 5 2 5 2 5 2 5 EW50SAG EW63SAG 7 5 0 5 1 2 2 0 2...

Страница 50: ...PF is superimposed on the operating characteristic curve of the MCCB as shown in Fig 3 9 by converting the current of the PF to the low voltage side or the current of the MCCB to the high voltage side...

Страница 51: ...0 300 BW400SAG 2 3 P EW400SAG 3P 36 BW400RAG 2 3 4 P EW400RAG 3 4 P 50 BW400HAG 2 3 4 P EW400HAG 3 4 P 70 BW400EAG 2 3 P EW400EAG 3P 30 350 400 BW400SAG 2 3 P EW400SAG 3P 36 BW400RAG 2 3 4 P EW400RAG...

Страница 52: ...rrent where the MCCB is installed is less than its breaking capacity Note 4 Selective trip coordination is available AAG BW32 1 5 1 3 5 10 15 20 30 32 Note 3 BW50 1 5 1 5 10 15 20 30 32 40 50 Note 3 B...

Страница 53: ...ote 2 Selective trip coordination is available Instantaneous trip current must be adjusted for coordination Note 3 Selective trip coordination is available Make sure however that the short circuit cur...

Страница 54: ...rature 3 4 2 Thermal characteristics of wire The temperature rise of wires due to overcurrent depends on the let through current and the continuous current carrying time The relationship between the t...

Страница 55: ...r temperatures reach 100 C starting from no load conditions at an ambient temperature for the wiring of 30 C Table 3 9 b Conductor speci cations Resistor temperature coef cient D 1 D 0 00427 1 C 234 C...

Страница 56: ...aracteristics of the MCCB Table 3 10 shows the combinations of MCCBs and PVC wires available for protection in the short time region Protection for wires in the short circuit region can be determined...

Страница 57: ...2 2 5 18 30 50 6 95 0 06 0 082 2 5 18 40 50 60 75 100 125 50 20 0 0 62 1 31 10 42 BW160JAG EW160JAG 125 150 160 50 24 5 1 28 1 31 10 42 BW250JAG EW250JAG 175 200 225 250 50 24 5 1 28 1 31 10 42 BW32SA...

Страница 58: ...1 0 0 178 0 21 4 24 40 50 60 75 100 125 30 10 0 1 65 3 35 16 56 BW160JAG EW160JAG 125 150 160 30 26 0 3 15 3 35 16 56 BW250JAG EW250JAG 175 200 225 250 30 26 0 3 15 3 35 16 56 BW32SAG EW32SAG 3 5 10 1...

Страница 59: ...ew cycles immediately after starting the DC component will overlap The magnitude of the asymmetrical current can be obtained from the relations given in Fig 3 14 and 3 15 These two diagrams are used a...

Страница 60: ...10 55 163 6 196 3 200 Note Motor full load currents are based on FUJI s standard type totally enclosed induction motors Check the value of the full load current before using Fig 3 16 Motor breaker pro...

Страница 61: ...5 4 86 5 BM3RSB BM3VSB BM3VSB BM3VHB SC 0 05 3 7 6 75 8 1 8 BM3RSB BM3RHB SC 4 0 5 5 10 12 12 BM3VSB BM3VHB SC 4 1 5 1 7 5 13 25 15 9 16 SC N1 11 19 5 23 4 24 BM3VSB BM3VHB SC N2 15 26 31 2 32 SC N2S...

Страница 62: ...are large instantaneous trip type MCCBs are used This is because standard MCCBs for line protection are provided with bimetal elements as tripping devices which have limited overcurrent withstand valu...

Страница 63: ...125SAG BW125RAG BW50HAG 75 BW100AAG BW100EAG SC N2S TR N3 3 40 11 100 BW125JAG BW125SAG BW125RAG BW50HAG SC N3 54 15 100 BW125JAG BW125SAG BW125RAG BW50HAG SC N4 TR N5 3 68 18 5 125 BW125JAG BW125SAG...

Страница 64: ...SC N2 TR N2 3 27 15 60 BW125JAG BW125SAG BW125RAG BW125HAG 75 BW100EAG SC N2S TR N3 3 34 18 5 60 BW125JAG BW125SAG BW125RAG BW125HAG 100 BW100EAG SC N2S TR N3 3 42 22 75 BW125JAG BW125SAG BW125RAG BW1...

Страница 65: ...ux in the core Only a slight exciting current is needed to generate the ux ows through the primary winding The following relationship exists between the induced voltage e the instantaneous value of th...

Страница 66: ...uit current at 220V 2 5 kA BW32AAG 3P005 BW32AAG 3P010 BW32AAG 3P015 BW32SAT 3P015 BW32SAT 3P020 BW32SAT 3P030 BW50SAT 3P040 5 kA BW32SAG 3P005 BW32SAG 3P010 BW32SAG 3P015 BW32SAT 3P015 BW32SAT 3P020...

Страница 67: ...peak inrush current of 25 times the rated current is used in the calculations Single phase 200 220V 100 115V Transformers Transformer capacity kVA 0 5 1 0 1 5 2 0 3 0 5 0 In Rated primary current rms...

Страница 68: ...current Ia at period t seconds can be stated as Ia IL D A ii Thermal equivalent current IB at period T seconds In Fig 3 22 the thermal equivalent current IB at period TL seconds is similar to that at...

Страница 69: ...hip between the primary input capacity and the allowable on load factor can be stated in an equation as u 50 Rated capacity Primary input capacity Allowable on load factor 2 This equation may be used...

Страница 70: ...ving its instantaneous tripping current at least two times the IL max calculated in ii Table 3 19 lists typical MCCBs that are selected to work with resistance welders that operate in synchronous or s...

Страница 71: ...t breakers with quick make quick break action are recommended for this type of circuit Fig 3 25 Residual electric charge in the capacitor Fig 3 26 Capacitor residual voltage Vc Em 2 Transient inrush c...

Страница 72: ...ZC V 3 In MCCB rated current effective value Ict Inrush current 0 01s after power is turned ON effective value Ic Ict 10 or Icn min k 1 5 margin coef cient for the allowable uctuation error V Line vo...

Страница 73: ...16 300 750 0 319 15 5 610 19 15 0 11 1200 60 220 0 97 4 4 1 03 50 0 06 12 17 10 SC 03 1 94 8 8 2 06 100 0 12 6 08 15 SC 0 2 91 13 2 3 10 150 0 19 4 06 20 SC 0 3 88 17 6 4 13 200 0 25 3 04 30 SC 4 1 5...

Страница 74: ...0 319 15 5 610 19 15 0 11 700 SC N14 60 220 0 97 2 5 1 03 50 0 06 12 17 5 SC 03 1 94 5 1 2 06 100 0 12 6 08 10 SC 03 2 91 7 6 3 10 150 0 19 4 06 15 SC 03 3 88 10 2 4 13 200 0 25 3 04 20 SC 03 5 13 1 5...

Страница 75: ...Commutation fails resulting in a short circuit occurring on the DC side Device break down A short circuit has resulted from the loss of SCR forward blocking capability Suspect an excessive junction t...

Страница 76: ...av ip 2 1 Effective I eff ip Effective I eff 1 2 ip Effective I eff 6 2 4S 2 3 ip 0 78ip Note The loads are resistive and the conduction angle of the device is 180 3 9 2 MCCB rated current When an MC...

Страница 77: ...he effective value base to compare with the characteristics of the protective device Fig 3 31 shows an example of a coef cient curve for converting to effective values Fig 3 30 Overcurrent immunity ch...

Страница 78: ...1 Thyristor overcurrent immunity characteristics 2 Instantaneous trip type circuit breaker operating characteristics 3 Semiconductor protection fuse operating characteristics Region B Region C 2 1 3 4...

Страница 79: ...urrent at or below 100A s 5SE A TWO POLE IN SINGLE PHASE CIRCUIT 33 APPLICATIONS OR A THREE POLE IN THREE PHASE CIRCUIT 33 APPLICATIONS 1 Breaking capacity at 600V AC Solid state contactor 3 10 Protec...

Страница 80: ...5 15 15 SS30 H SS30 H SS30 H SS50 H SS50 H SS80 H SS120 H BM3RSB 004 BM3RSB 6P3 BM3RSB 010 BM3RSB 013 BM3RSB 016 BM3RSB 032 BM3RSB 032 100 100 100 50 50 50 50 CR6L 30 CR6L 50 CR6L 50 CR6L 75 CR6L 100...

Страница 81: ...15 5 5 0 75 1 8 1 5 3 5 10 2 2 4 8 15 3 7 7 8 10 20 5 5 10 5 15 30 7 5 13 5 20 40 11 20 30 50 15 27 40 60 18 5 34 75 22 42 50 100 30 58 75 125 37 69 100 45 83 150 55 100 125 200 75 136 175 90 166 200...

Страница 82: ...kin effect 3 12 MCCBs for high frequency circuits Hydraulic magnetic type and solid state trip type MCCBs cannot be used in 400Hz circuits because their characteristics would vary considerably Since t...

Страница 83: ...C2 C5 and C6 at the end of the type description a standard product can be used for both AC and DC Only DC250V is indicated for DC rating DC125V is indicated for BW32SBG BW50SBG and BW63SBG For those a...

Страница 84: ...BW630RAS 3P CP BW800RAS 3P CP 800V 1000V BW400RAS 4P CP BW630RAS 4P CP BW800RAS 4P CP Note 1 While 400 800AF can be used for the standard products of DC500V 3 pole item and DC600V 4 pole item only DC...

Страница 85: ...supply output and use an MCCB with the same capacity at the input side Consider the following points when selecting an MCCB UPS overload withstand 125 for 10 minutes 150 for 1 minute With overcurrent...

Страница 86: ...W50EAG 3P030 3 RYS302S3 BW50EAG 3P040 EW50EAG 3P040 4 RYS402S3 BW50EAG 3P050 EW50EAG 3P050 5 RYS502S3 0 5 Low base speed series RYS501A3 BW50EAG 3P015 EW50EAG 3P015 1 5 RYS152A3 2 5 RYS252A3 BW50EAG 3...

Страница 87: ...lame for circuit problems However low voltage wiring systems tend to have low charging current to ground and the sensitivity of protective relays makes it hard to choose a feeder for ground faults in...

Страница 88: ...he phase conductor to the ground for the exposed parts of the load equipment Contact voltage of 50V max Zero impedance short circuiting from the phase conductor in the equipment to the protective cond...

Страница 89: ...lly within 5 s s 7ITH INSTANTANEOUS TRIPPING CHARACTERISTICS A IS THE SMALLEST current that can trip the MCCB automatically 50V t Id RA RA Same as that on the left Id Ground fault current at the rst o...

Страница 90: ...88...

Страница 91: ...vironments 4 2 1 High temperature high humidity applications 91 4 2 2 Cold climate applications 91 4 2 3 High altitude applications 91 4 2 4 Application to special atmospheres 92 4 3 Connection precau...

Страница 92: ...ons for FUJI MCCB performance If the ambient conditions under which a circuit breaker is to be used differ signi cantly from these standards the circuit breaker s characteristics may differ considerab...

Страница 93: ...enclosure 4 2 2 Cold climate applications At 5 C or lower temperatures MCCB metallic parts and insulators may become brittle and the viscosity of the lubricant used in its mechanical parts changes the...

Страница 94: ...ll accelerate corrosion There is less chance of corrosion with humidity at 65 or lower No problems 0 to 0 04 to 0 5 to 100 RH 65 Standard parts Parts treated for anti corrosion and A C or B 1 2 Chlori...

Страница 95: ...s 4 3 1 Reversed connection The power supply side and the load side are indicated on the following products The breaking capacity for power supply reverse connection is different than that for regular...

Страница 96: ...t An MCCB may trip if the overcurrent detection device detects higher than normal transient current like motor starting current or transformer exciting inrush current One way to prevent this is to sel...

Страница 97: ...ns 5 2 1 Initial inspection 98 5 2 2 Periodic inspections 98 5 2 3 Inspection following overcurrent tripping 99 5 3 Replacement recommendations 5 3 1 Recommendations for MCCB deterioration diagnosis a...

Страница 98: ...Y MECHANISM Breaker tripping The breaker trips in a closed circuit with less than the rated current s 4HE AMBIENT TEMPERATURE IS ABNORMALLY HIGH OR higher Use ventilation or some other means to lower...

Страница 99: ...le Increase the power supply capacity transformer capacity etc s AKE RUN AND RESET DO NOT WORK PROPERLY BECAUSE THE moving distance of the control mechanism is not properly adjusted Re adjust the stro...

Страница 100: ...s due to excessive switching or contact wear This is why periodic inspections are important Table 5 4 shows inspection standards and Table 5 5 shows inspection procedures Table 5 2 Initial inspection...

Страница 101: ...around the terminals on the power supply side to make sure no dust or oil has accumulated Check to make sure that dust or other foreign matter has not bridged the gap provided to increase creepage dis...

Страница 102: ...e number of switching operations determines the durability of an MCCB in frequent switching applications MCCBs should be replaced before they exceed the value in any column in Table 5 9 Table 5 9 Swit...

Страница 103: ...t circuit current calculation 6 1 Calculating short circuit current 6 1 1 Calculation objective 102 6 1 2 Calculation formula 102 6 1 3 Calculating short circuit current for three phase circuits 102 6...

Страница 104: ...apacity or breaking capacity Q MVA o j X1 PT kVA VT V ZT RT j XT jX3 o j X3 Cable R5 n jX5 n R5 n j X5 n Total capacity PM kVA PM kVA 1 5x kW sum total Cable R4 jX4 R4 j X4 jX2 o j X2 F j Xm Fig 6 1 s...

Страница 105: ...hown in Fig 6 2 and be very careful connecting impedance in series or in parallel between the busbar and fault point F when creating the impedance map s 3TEP 5NIFYING IMPEDANCE Take the impedance map...

Страница 106: ...96 2000 6 3 1 3 6 2 7 5 0 65 7 47 5 0 1 1 5 39 7 0 0 7 6 96 Table 6 2 Impedance of rubber and plastic sheathed cables Impedance of 600V 3 core CV EV PV VV round stranded cable at 50Hz Nominal conducto...

Страница 107: ...bles connected in parallel Table 6 4 Bus bar and bus duct impedance examples 50Hz Data Furukawa Electric Co Ltd Material Rated current A Regular bus duct Conductor dimensions mm Resistance m Reactance...

Страница 108: ...ive stress on the latter Breaking capacity of a switching device or a fuse Value of prospective breaking current that a switching device or a fuse is capable of breaking at a stated voltage under pres...

Страница 109: ...ntaneous value of current attained during the breaking operation of a switching device or a fuse NOTE This concept is of particular importance when the switching device or the fuse operates in such a...

Страница 110: ...urrent characteristic Main circuit of a switching device All the conductive parts of a switching device included in the circuit which it is designed to close or open Main contact Contact included in t...

Страница 111: ...ed conditions NOTE The speci ed conditions may relate to the method of initiation e g by an ideal switching device or to the instant of initiation e g leading to the maximum prospective peak current...

Страница 112: ...ent coordinate of the intersection between the time current characteristics of two overcurrent protective devices Thermal overload relay or release trip device Inverse time delay overload relay or rel...

Страница 113: ......

Страница 114: ...s such as for atomic energy control aerospace use medical use passenger vehicle and traffic control are requested to consult with Fuji Electric FA Customers are requested to prepare safety measures wh...

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