Fuji Electric BW32AAG - Selection and Application

33
Chapter 3
CONTENTS
Selection and application
3-1 Selection check points
3-1-1 MCCB selection check points ...................................................................................... 34
3-1-2 Selecting and MCCB ratings ........................................................................................ 36
3-1-3 Overcurrent protection principle ................................................................................... 37
3-1-4 Protective coordination ................................................................................................ 37
3-2 Cascade trip applications
3-2-1 Conditions for cascade (backup) trip coordination ......................................................40
3-2-2 Criteria for cascade (backup) trip coordination ...........................................................40
3-3 Selective trip applications
3-3-1 Selective trip coordination of breakers ........................................................................43
3-3-2
Selective trip coordination between MCCBs and high-voltage side protective devices ......48
3-3-3 Selective trip coordination with a high-voltage fuse .....................................................49
3-4 Wiring protection
3-4-1 Description ..................................................................................................................52
3-4-2 Thermal characteristics of wire ...................................................................................52
3-4-3 Application of protective devices .................................................................................54
3-5 Motor circuit applications
3-5-1 Description ..................................................................................................................57
3-6 Applications on the primary side 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 applications
3-7-1 Arc welders .................................................................................................................66
3-7-2 Resistance welders .....................................................................................................66
3-8 Selecting an MCCB for capacitor circuit
3-8-1 Characteristics specific to capacitor circuits .................................................................69
3-9 MCCBs for semiconductor circuit
3-9-1 Faults and overcurrents in thyristor converters ...........................................................73
3-9-2 MCCB rated current ....................................................................................................74
3-9-3 Protecting thyristors from overcurrent .........................................................................75
3-10 Protecting SSCs using MCCBs or MMSs
3-10-1 For heater (resistive load) circuits ..............................................................................77
3-10-2 Motor circuits ..............................................................................................................78
3-11 Protecting inverter circuits using MCCBs
3-11-1 Inverter circuits ...........................................................................................................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
3-16-1 Grounding methods and ground fault protection in system applications ....................85