MR-W3-57-400-25AGA MCCB Unit

Module Feature

MR-W3-57-400-25AGA is a 3-pole molded case circuit breaker with rated current 400A and 25kA ultimate short-circuit breaking capacity.

It is equipped with adjustable electronic trip unit, supports long-time overload, short-time delay, instantaneous short-circuit and earth fault protection. It has manual operating handle, optional electrical motor operator and auxiliary/alarm contact block. Compact frame design, good anti-vibration and thermal stability, widely used for factory auxiliary circuit, pump, fan and distribution feeder loop. It is stocked as maintenance spare for industrial power distribution system.

Working principle

Built-in current transformers sample three-phase current signals and transmit data to electronic trip unit.

Trip unit continuously compares real-time current with configured protection curves. When overload, short circuit or earth fault occurs, it triggers the release mechanism rapidly to separate main contacts and cut off fault circuit. Operation records and fault codes are stored internally for post-fault analysis. It supports external communication expansion module for remote status uploading to PLC and SCADA system.

Onboard components

Main contact set, arc extinguishing chamber, CT sensor group, electronic protection trip unit, operating mechanism, auxiliary contact block, alarm contact, front operation handle, status indicator window and reinforced insulated housing.

LED indicators

Front status indicators show breaker ON, breaker OFF and fault trip. Detailed protection alarm codes are displayed on trip unit panel.

Hardware self‑diagnosis

Built-in supervision detects trip coil continuity, CT signal loss, internal power loss and trip unit hardware anomaly. Protection parameter setting and fault log reading are finished by manufacturer dedicated configuration software.

Programming software

Manufacturer power distribution commissioning tool, used for overload curve, short circuit threshold, earth fault setting and communication address configuration.

Electrical & Process Parameters

Model:MR-W3-57-400-25AGA Brand:OEM distribution spare Device type:3P 400A molded case circuit breaker Function:Overload, short circuit and earth fault protection for three-phase low voltage feeder circuit

Mechanical & Structure

Mounting:Cabinet fixed installation Protection class:IP30 front panel, IP20 terminal compartment Housing:Reinforced insulated MCCB housing

Environmental

Operating temperature:-10℃ ~ +55℃ Storage temperature:-40℃ ~ +85℃ Ambient humidity:5~95% non‑condensing

Certification:CE, IEC 60947-2 Status:Original power distribution spare

Installation

Isolate upstream power supply before replacement.

Check primary wiring and secondary control circuit, confirm three-phase sequence, set protection parameters according to design, test manual/electric closing, tripping and protection function after commissioning.

Interface

Primary power terminal block for L1/L2/L3, secondary screw terminal block for auxiliary contact, alarm contact and communication expansion.

Diagnostic

Failed to close: Mechanical interlock triggered, operating coil damage or trip lock active. Instantaneous false trip: Short circuit downstream, wrong instantaneous setting or CT wiring error. Earth fault alarm: Leakage current, neutral cross interference or earth threshold improperly set.

Product Brief

MR-W3-57-400-25AGA circuit breaker, 3-pole 400A 25kA molded case breaker spare for industrial low voltage feeder distribution cabinet replacement.

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