
C O N T E N T S
Chapter
1
Protecting low-voltage circuits
1-1 Description
...................................................................... 4
1-2 Overcurrent protection .................................................... 5
1-3 Phase-loss
protection
..................................................... 6
Chapter
2
Operating characteristics and
performance
2-1 Overcurrent tripping characteristics ................................ 8
2-2 Breaking
performance
.................................................. 11
2-3 Overload switching performance .................................. 26
2-4 Performance with current at 100% . ............................... 27
2-5 Durability
....................................................................... 29
2-6 Withstand voltage performance .................................... 31
2-7 Handle operating force and angle ................................. 32
Chapter
3
Selection and application
3-1 Selection check points .................................................. 34
3-2 Cascade trip applications ............................................. 40
3-3 Selective trip applications ............................................. 43
3-4 Wiring
protection
........................................................... 52
3-5 Motor circuit applications .............................................. 57
3-6 Applications on the primary side of transformers ......... 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 inverter circuits using MCCBs .................... 79
3-12 MCCBs for high frequency circuits .............................. 80
3-13 MCCBs for DC circuit applications .............................. 81
3-14 MCCBs for UPS applications ....................................... 83
3-15 MCCBs for servo amplifier applications ....................... 84
3-16 Ground fault protection in system applications ............ 85
Chapter
4
Environment and usage
precautions
4-1 Standard
conditions
...................................................... 90
4-2 Application to special environments ............................. 91
4-3 Connection
precautions
................................................ 93
4-4 Malfunction due to transient inrush current .................. 94
Chapter
5
Maintenance inspections
5-1 Faults and causes ......................................................... 96
5-2 Periodic inspections ...................................................... 98
5-3 Replacement
recommendations
................................. 100
Chapter
6
Short-circuit current calculation
6-1 Calculating short-circuit current .................................. 102
Glossary
....................................................................... 106