Mitsubishi NF630-SEW 4P Adjustable Circuit Breaker 300-630A

The Mitsubishi NF630-SEW is a 4-pole molded case circuit breaker (MCCB) from the NF series, designed for low voltage distribution and motor protection. The breaker features an adjustable thermal-magnetic trip unit with a current rating range from 300A to 630A, suitable for protecting feeders, transformers, and large motors in industrial installations. It complies with IEC 60947-2 and JIS C 8201 standards.

Electrical Ratings

• Rated insulation voltage (Ui): 800 V AC.

• Rated impulse withstand voltage (Uimp): 8 kV.

• Rated operational voltage (Ue): AC 600 V (50/60 Hz).

• Rated current (In) adjustable: 300 A, 350 A, 400 A, 450 A, 500 A, 550 A, 600 A, 630 A (via rotary dial).

• Number of poles: 4 (three phases + neutral protected).

• Breaking capacity (Icu): 50 kA at 600 V AC (IEC 60947-2).

• Making capacity (Icm): 105 kA.

Trip Unit Characteristics

The NF630-SEW uses a thermal-magnetic trip mechanism. The thermal part (overload protection) is adjustable from 0.8 to 1.0 times the set current; the magnetic part (short-circuit protection) is fixed at 10 times the set current (Irm = 10 x In). The trip unit is interchangeable, allowing replacement without removing the breaker. Ambient temperature compensation is provided from -20°C to +60°C. The thermal tripping delay follows class 10A (for motor protection) or class 20 selectable via internal jumper.

Adjustment Mechanism

A front-mounted rotary dial with clearly marked positions allows the user to select the desired continuous current. A scale shows the multiplier relative to the frame rating (630A). The dial includes a sealable cover to prevent unauthorized changes. Additionally, the magnetic trip threshold can be adjusted (4x to 12x In) on request – the standard NF630-SEW has fixed magnetic trip at 10x In. For ground fault protection, an optional add-on module (NFC63-SW) can be installed.

Mechanical Features

The breaker has a robust molded case of glass-reinforced polyamide (UL94 V-0). It provides visible contact status indicators (red/green) and a push-to-trip test button. The operating mechanism is toggle type with quick-make, quick-break action. Mechanical life: 8,500 operations. Electrical life: 1,500 operations at rated current. The terminals accept lug or busbar connections: wire size 240 mm² (copper) or 185 mm² (aluminum). Tightening torque is 20 Nm.

Protection Functions

Overload (L) protection: inverse time curve with I²t characteristic. Short-circuit (I) protection: instantaneous trip within 10 ms. The breaker also provides phase imbalance sensitivity (optional). A built-in trip indicator (red flag) shows if the breaker tripped due to overload/short or manual operation. The 4-pole version ensures neutral conductor protection even in unbalanced three-phase systems.

Dimensions and Mounting

Dimensions (W x H x D): 140 mm x 200 mm x 110 mm. Weight: 3.8 kg. Mounting: screw fixing on a flat panel or DIN rail (with adapter). The breaker can be mounted vertically or horizontally (performance derating of 10% for horizontal mounting). Minimum clearance between adjacent units: 20 mm. Terminal covers are included for finger-safe protection (IP20).

Environmental Conditions

Operating temperature: -25°C to +70°C (derating above 50°C: reduce current by 1.5% per °C). Storage temperature: -40°C to +85°C. Altitude: up to 2000 m. Pollution degree 3. Vibration resistance: 5 g at 10–150 Hz. The breaker is RoHS and REACH compliant, with no hazardous substances.

Accessories

Available accessories: shunt trip (SD), undervoltage release (UVT), auxiliary contact (AX), alarm contact (AL), handle extension, and padlockable handle in OFF position (up to 3 padlocks). The auxiliary contact block (1NO+1NC) is field installable. For remote operation, a motor operator (MO) can be added – Model MO-630S.

Standards and Certifications

Certified to IEC 60947-2 (edition 5), UL 489 (for US market, file E58991), CSA C22.2 No. 5.1, CCC (China), and CE marking. The NF630-SEW also meets marine specifications (Lloyd’s Register). Short-circuit current rating (SCCR) for industrial control panels is 50 kA.

Typical Applications

Used as main disconnect for machine tools, HVAC compressors, pumping stations, and injection molding machines. The adjustable current range makes it suitable for motors from 150 kW to 315 kW at 400 V. In distribution panels, it protects busbars and cable feeders against overloads and faults. The 4-pole version is essential for systems where neutral conductor overload is possible (e.g., harmonic rich loads).

Ordering Code

Mitsubishi NF630-SEW (product code: NF630SEW). The breaker is shipped with terminal covers and mounting screws. Manual available as Mitsubishi Electric catalog LVA-E002. For spare parts, the trip unit is model TUS630-SEW.