Mitsubishi Electric NV400-SW 3‑Pole 300A Earth Leakage Circuit Breaker

The Mitsubishi NV400-SW is a high‑performance earth leakage circuit breaker (ELCB) from the WS‑V (World Super V) series. It is designed for 3‑phase distribution networks, rated at 300A continuous current and 400V AC. The breaker provides adjustable earth leakage sensitivity (30 mA, 100 mA, 200 mA, 500 mA, 1 A) and time delay settings. It also includes thermal‑magnetic overload and short‑circuit protection with a breaking capacity of 45 kA at 415V AC. The NV400-SW is suitable for main switchboards, motor circuits, and industrial power distribution.

Technical Specifications

Protection Functions

The NV400-SW integrates multiple protection mechanisms:

• Overload protection: Thermal (bimetallic) trip with a fixed class 10/20 characteristic. The trip current (Ir) is adjustable via a rotary dial (0.8–1 x In).

• Short‑circuit protection: Magnetic instantaneous trip at 10 × In (fixed).

• Earth leakage protection: Electronic leakage detection with adjustable sensitivity and time delay (IΔt). The leakage sensor monitors the vector sum of the three phase currents. The breaker can be set to “instantaneous” (≤ 0.1 s) or time‑delayed (0.1–2 s) to achieve selectivity with downstream RCDs.

• Voltage‑independent operation: The thermal‑magnetic part operates without auxiliary power; the electronic leakage part requires minimal power from the monitored circuit.

Mechanical Features

The breaker has a toggle‑type operating handle with ON/OFF indication. It includes a padlockable handle (up to three padlocks) for lockout/tagout (LOTO) safety. The housing is made of glass‑reinforced polyamide (UL94 V‑0). The terminals accept copper cables up to 185 mm² (for 300A rating). An optional auxiliary contact and shunt trip release are available as accessories.

Standards and Compliance

The NV400-SW complies with IEC 60947‑2 (low‑voltage circuit breakers), EN 61008-1 (residual current circuit breakers), and UL 489 (with certain conditions). It is CE marked and RoHS compliant. The breaker has a high resistance to vibration (4g at 10–55 Hz) and shock (10g). Operating temperature: -5°C to +40°C.

Applications

Typical uses include main incoming protection for industrial control panels (MCCs), motor feeder circuits (with adjustable Ir for motor protection), and sub‑distribution in commercial buildings. The adjustable earth leakage sensitivity makes it suitable for circuits with sensitive electronics (e.g., PLCs, drives) where nuisance tripping must be avoided.

Conclusion

The Mitsubishi NV400-SW 3P 300A earth leakage circuit breaker combines high breaking capacity, adjustable protection parameters, and compact dimensions, offering reliable protection for industrial and commercial power systems.