Table Of Contents - Mitsubishi NF-S Series Technical Notes

We have the pleasure of providing all our customers with the technical information for Mitsubishi
moulded case circuit breakers. This indicates the fundamental data of our circuit breakers
regarding the applicable standards, constructional principles, and operational performances.
Please refer to the catalogue of our circuit breakers for details of specifications.
Also please stand in need of the handling and maintenance manual for maintaning the circuit
breakers in service continuously.
We do hope they are available for all our customers to built more efficient systems.
CONTENTS
1. INTRODUCTION ............................................... 2
2. FEATURES ....................................................... 3
2.1 Arc-Extinguishing Device - ISTAC .................. 3
2.2 Digital ETR ......................................................... 4
3. CONSTRUCTION AND OPERATION ............... 6
4. CHARACTERISTICS AND
PERFORMANCE ............................................. 11
4.1 Overcurrent-Trip Characteristics ................... 11
4.2 Short-Circuit Trip Characteristics .................. 11
4.3 Effects of Mounting Attitudes ........................ 12
4.4 DC Tripping Characteristics of AC-Rated
MCCBs .............................................................. 12
4.5 Frequency Characteristics ............................. 12
4.6 Switching Characteristics ............................... 13
4.7 Dielectric Strength ........................................... 13
5. CIRCUIT BREAKERS SELECTION ............... 14
5.1 Circuit Breakers Selection Table ................... 14
6. PROTECTIVE CO-ORDINATION ................... 39
6.1 General ............................................................. 39
6.2 Interrupting Capacity Consideration ............. 40
6.3 Selective-Interruption ...................................... 41
6.4 Cascade Back-up Protection .......................... 46
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6.5 I t Let-Through Characteristics and Current
Limiting Characteristics .................................. 48
6.6 Protective Coordination with Wiring ............. 49
6.7 Protective Coordination with
Motor Starters .................................................. 52
6.8 Coordination with Devices on the
High-Voltage Circuit ........................................ 54
7. SELECTION .................................................... 57
7.1 For Motor Branch Circuits .............................. 57
7.2 For Lighting and Heating Branch Circuits .... 57
7.3 For Main Circuit ............................................... 58
7.4 For Welding Circuits ....................................... 58
7.5 For Transformer-Primary Use ........................ 60
7.6 For Capacitor Circuits ..................................... 61
7.7 For Thyristor Circuits ...................................... 62
7.8 Selection of MCCBs in inverter circuit .......... 68
8. ENVIRONMENTAL CHARACTERISTICS ...... 70
8.1 Atmospheric Environment .............................. 70
8.2 Vibration-Withstand Characteristics ............. 71
8.3 Shock-Withstand Characteristics .................. 72
9. SHORT-CIRCUIT CURRENT
CALCULATIONS ............................................ 73
9.1 Purpose ............................................................ 73
9.2 Definitions ........................................................ 73
9.3 Impedances and Equivalent Circuits of
Circuit Components ........................................ 73
9.4 Classification of Short-Circuit Current .......... 76
9.5 Calculation Procedures .................................. 77
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