Mitsubishi NV400-SW 3-Pole Molded Case Circuit Breaker for Industrial Power Distribution

Product Overview

The Mitsubishi NV400-SW is a 400 ampere, three-pole molded case circuit breaker (MCCB) belonging to the NV series. This device is designed for power distribution and motor protection in industrial electrical systems, offering reliable overcurrent protection against overloads and short circuits. The NV400-SW is rated for operation at 600V AC maximum and is suitable for use as the main disconnect or branch circuit protection in switchboards, panelboards, and motor control centers. Its compact construction and high interrupting capacity make it a preferred choice for demanding applications such as manufacturing plants, commercial buildings, and infrastructure projects.

Key Features of Mitsubishi NV400-SW

The NV400-SW incorporates a thermal-magnetic trip mechanism. The thermal element provides inverse-time protection against sustained overloads, while the magnetic element offers instantaneous protection against high-magnitude short circuits. The circuit breaker features a fixed thermal trip rating of 400A with an adjustable magnetic trip setting (typically 5 to 10 times the rated current). The interrupting capacity is rated at 50 kA at 480V AC (specific values may vary; refer to nameplate). The breaker includes a rotary handle with an ON-OFF position indicator, and provisions for padlocking in the OFF position for safety during maintenance.

The NV400-SW is designed with a compact molded case made of high-strength thermoset material that provides arc resistance and mechanical durability. The breaker features line and load terminals suitable for copper or aluminum cables, with cage-type clamps for secure connections. The unit is rated for 100% continuous operation when used in an appropriate enclosure. Accessories such as auxiliary contacts, shunt trips, undervoltage releases, and alarm switches can be field-installed. The breaker complies with IEC 60947-2 and JIS C 8201-2 standards. The operating temperature range is -5°C to +40°C, with derating at higher temperatures.

Technical Specifications

• Manufacturer: Mitsubishi Electric Corporation

• Part Number: NV400-SW

• Product Type: Molded Case Circuit Breaker (MCCB)

• Number of Poles: 3

• Rated Current (In): 400 A

• Rated Operational Voltage (Ue): AC 600 V (50/60 Hz)

• Rated Insulation Voltage (Ui): 690 V AC

• Rated Impulse Withstand Voltage (Uimp): 6 kV

• Interrupting Capacity (Icu): 50 kA at 480 V AC (typical)

• Trip Type: Thermal-magnetic, fixed thermal, adjustable magnetic

• Magnetic Trip Setting: Adjustable (typically 5-10 x In)

• Terminal Type: Cage clamp, suitable for Cu/Al cables up to 240 mm²

• Padlockable: Yes (OFF position)

• Operating Temperature: -5 to +40 °C

• Storage Temperature: -20 to +60 °C

• Degree of Protection: IP20 (enclosed condition)

• Dimensions (W x H x D): 140 mm x 210 mm x 103 mm (approx.)

• Weight: Approximately 3.5 kg

• Standards: IEC 60947-2, JIS C 8201-2

Functional Description

During normal operation, the NV400-SW allows current to flow through its contacts with negligible voltage drop. When an overload current (1.05 to 7.2 times In) persists, the bimetallic thermal element bends, eventually tripping the breaker via a latch mechanism. The trip time is inversely proportional to the square of the current. For short-circuit currents above the magnetic pickup setting, the electromagnet instantly pulls in and releases the latch, tripping the breaker within milliseconds to limit fault energy. The breaker's arc chutes extinguish the arc by dividing it into small segments and cooling it. After tripping, the handle moves to a mid-position (trip-indicating) to alert the operator. The breaker can be manually reset by moving the handle to OFF then ON.

Applications

The Mitsubishi NV400-SW is used as a main breaker in industrial distribution panels, feeder protection for motor control centers, protection for large HVAC equipment, welding machine power supplies, and as a disconnect for transformers and capacitors.