Mitsubishi NF800-SEP User Manual

ADVANCED AND EVER ADVANCING
MOULDED CASE CIRCUIT BREAKERS
TECHNICAL NOTES
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Mitsubishi NF800-SEP Specifications

General

Model	NF800-SEP
Category	Circuit breakers
Rated Current (In)	800A
Rated Voltage (AC)	690V
Trip unit	Electronic
Mounting	Fixed
Standards	IEC 60947-2
Poles	3P

Summary

2. FEATURES – Advanced MCCB Design Technology & Performance

2.1 Arc-Extinguishing Device – ISTAC

Details on the ISTAC technology for improved current limiting and breaking.

Vapor jet control (VJC)

2.2 Digital ETR (Electronic Trip Relay)

Digital detection of the effective value

How the digital ETR detects effective current values, minimizing errors.

Automatic Tripping Devices

Thermal-Magnetic Type (100~630A Frame)

Description of thermal-magnetic trip unit operation.

Hydraulic-Magnetic Type (30~60A Frame)

Principle of Electronic Trip Relay (ETR) Operation

Detailed explanation of how ETRs function.

4. CHARACTERISTICS AND PERFORMANCE

4.1 Overcurrent-Trip Characteristics (Delay Tripping)

Tripping times for overcurrents at different levels.

4.1.1 Ambient Temperature and Thermal Tripping

How ambient temperature affects thermal tripping.

4.1.2 Hot-State Tripping

4.2 Short-Circuit Trip Characteristics (Instantaneous Tripping)

Behavior of the instantaneous trip function.

5. CIRCUIT BREAKER SELECTION

5.1 Circuit Breaker Selection Table

A table to aid in selecting appropriate circuit breakers.

6. PROTECTIVE CO-ORDINATION

Selective-Interruption(Discrimination)

Ensuring only the faulty circuit device trips.

Cascade Back-Up Protection

An economical approach using upstream breaker capacity.

6.5 I²t let-Through and Current Limiting Characteristics (440 VAC)

I²t let-through characteristics

Graphs illustrating I²t let-through values.

Current limiting characteristics

Graphs showing maximum let-through current.

6.6 Protective Coordination with Wiring

6.6.1 General Considerations

6.6.2 600V Vinyl-Insulated Wire (Overcurrent)

6.7 Protective Coordination with Motor Starters

6.7.1 Basic Criteria for Coordination

Criteria for coordinating MCCBs with starters.

6.7.2 Levels of Protection (Short Circuit)

6.7.3 Motors with Long Starting Times

6.7.4 Motor Breakers (M Line MCCBs) and Magnetic Contactors

6.7.5 Motor Thermal Characteristics

6.7.6 Motor Starting Current

6.8 Coordination with Devices on the High-Voltage Circuit.

6.8.1 High-Voltage Power Fuse

Coordinating MCCBs with HV power fuses.

6.8.2 Electronic MCCBs and HV PF

Coordination of electronic MCCBs with HV PF.

6.8.3 MCCBs and HV-Side OCR

Coordinated OCR and Electronic MCCB Characteristics

7. SELECTION

7.1 Motor Branch Circuits

Selecting MCCBs for motor branch circuits.

7.1.1 General Considerations

7.2 For Lighting and Heating Branch Circuits

7.3 For Main Circuits

7.3.1 For Motor Loads

7.4 For Welding Circuits

7.5 MCCBs for Transformer-Primary Use

Table 7.2 Transformer Excitation Surge Currents

Table 7.3 Transformer Capacities and Primary-Side MCCBs

7.7 MCCBs for Thyristor Circuits

1. MCCB Rated Currents

Factors for determining MCCB rated currents.

7.8 Selection of MCCBs in inverter circuit

7.8.1 Cause of distorted-wave current

7.8.2 Selection of MCCBS

Selection criteria for MCCBs in inverter circuits.

8. ENVIRONMENTAL CHARACTERISTICS

8.1 Atmospheric Environment

8.1.1 High Temperature Application

9. SHORT-CIRCUIT CURRENT CALCULATIONS

9.3 Impedances and Equivalent Circuits of Circuit Components

Calculating impedances and using equivalent circuits.

9.5 Calculation Procedures

9.5.1 Computation Methods

Methods for calculating short-circuit current.

Percentage Impedance Method

Explanation of the percentage impedance method.

Ohmic Method

Explanation of the ohmic method.