GE MS31W25 Air Circuit Breaker Unit

Module Feature

MS31W25 is a 3-pole drawout type air circuit breaker under GE Type S series, with 2500A frame rating and non-automatic release configuration.

It adopts withdrawable racking structure with primary and secondary isolating contacts. It has mechanical interlock to prevent racking in/out under closed state. It is designed for main incoming bus, bus tie and large motor feeder protection in heavy industrial power houses. It is widely used for legacy GE main switchboard spare replacement and low voltage distribution retrofit projects.

Working principle

The breaker conducts load current through main silver alloy contacts.

Under manual operation, the closing mechanism locks the contacts closed. For this non-auto variant, it has no integral electronic trip unit; fault protection is implemented by external protective relays. When a trip signal is received, the shunt trip releases the operating mechanism to open the main contacts and cut the fault circuit.

Onboard components

Main contact assembly, arc chute stack, spring charged operating mechanism, drawout carriage, primary isolation contacts, secondary control terminal block, mechanical position indicator, racking interlock device.

LED indicators

No built-in LED. Breaker ON/OFF, racked-in/racked-out and trip status are shown by mechanical flag.

Hardware self‑diagnosis

No embedded electronic self-diagnosis. Contact wear, contact resistance and operating mechanism health are checked during periodic maintenance and insulation resistance test.

Programming software

No supporting configuration software.

Electrical & Process Parameters

Model:MS31W25 Brand:GE Device type:Drawout air circuit breaker Rated frame current:2500A Function:Manual switching and fault isolation for low voltage main distribution circuits

Mechanical & Structure

Mounting:Switchgear compartment drawout cradle installation Protection class:IP20 Housing:Metal insulated breaker enclosure

Environmental

Operating temperature:-20℃ ~ +70℃ Storage temperature:-40℃ ~ +85℃ Ambient humidity:5~95% non‑condensing

Certification:CE, IEC

Status:Original GE legacy power distribution spare

Installation

Insert the breaker into matched Type S switchgear cell, perform racking operation following interlock sequence.

Torque primary connections properly, test mechanical interlock, shunt trip function and secondary wiring continuity before energizing.

InterfacePrimary power isolation contacts, secondary control wiring terminals, racking drive interface.

Diagnostic

Failed to close: Spring discharged, interlock locked or mechanical jam. Overheating: Loose primary contact connection or contact surface burning. Cannot rack: Interlock not released or misaligned carriage guide.

Product Brief

GE MS31W25 2500A drawout air circuit breaker, legacy Type S main switching component for industrial low voltage switchgear maintenance replacement.