EXM3 MCCB – 100A/250A/630A

EXM3 AC MCCB – Molded Case Protection From 10A to 1250A

The EXM3 from HUYU Electric provides molded case circuit breaker protection for both commercial and industrial applications. The EXM3 is composed of seven frame sizes and supports a variety of current ratings from 10A up to 1250A. The EXM3 Circuit Breaker has been third-party tested to meet IEC 60947-2 and GB/T 14048.2 Standards. Additionally, there are three different performance ratings to choose from: C (Basic), S (Standard), and H (High). By doing this, you can match trip ratings to the fault level, while avoiding overpaying for your protection.

The EXM3 MCCB breaker is well suited for panel builders and project buyers due to its flexibility in installation methods, as well as being available with two different trip units to fit various applications. The EXM3 can be equipped with either a thermal-magnetic or an electronic trip unit and can be installed in fixed, plug-on, or draw-out configurations. A wide array of clip-on accessories — including shunt releases, undervoltage releases, motor operators, auxiliary contacts, and alarm contacts — transforms the basic protection device into a comprehensive control solution. Buyers currently sourcing molded case circuit breakers from Schneider Compact NSX, ABB Tmax, Siemens 3VA, Eaton, L&T, or Chint can expect the EXM3 to provide similar IEC 60947-2 performance, with factory-direct OEM/ODM pricing and private label options.

Frame Sizes & Performance Levels – Right-Sized Protection From 10A to 1250A

The EXM3’s seven frame sizes span the most commonly specified MCCB range. With three performance levels — C (Basic), S (Standard), and H (High) — you can match breaking capacity to your installation’s prospective fault current. A MCCB 100A circuit can use a C-level frame, while a MCCB 630A main incomer benefits from the H-level’s higher Icu. Mechanical life goes up to 20,000 operations on smaller frames and 10,000 on the 400–630A range. Electrical life at 415V is rated at 10,000 cycles for smaller frames and 8,000 to 5,000 cycles for larger frames.

Technical Specifications

Factory-Direct MCCB Supply for Panel Builders & Project Buyers

Buyer’s Guide

How to Specify an MCCB – Frame Size, Breaking Level & Trip Unit

A practical guide to selecting the correct EXM3 molded case circuit breaker for branch and main protection.

1. Choosing the Frame Size and Current Rating

The EXM3’s seven frame sizes provide precise matching to the load. For branch circuits up to 63A, the EXM3-63 in 1P or 2P is suitable. A MCCB 160A or MCCB 250A covers most commercial feeder and sub-main needs. For industrial main incomers, a MCCB 630A from the EXM3-630 frame provides up to 100kA Icu in H-level configuration. Selecting the closest frame to the actual load current avoids the cost of an oversized frame and the physical footprint it occupies in the switchboard.

2. C, S, or H Breaking Level?

C-level (Basic) suits installations with low prospective fault current — typically cable-fed sub-circuits far from the supply transformer. S-level (Standard) covers most commercial and light industrial applications. H-level (High) is required for main incomers, circuits close to large transformers, and installations where the available fault current exceeds the S-level rating. At 415V, H-level provides up to 100kA Icu — sufficient for the most demanding LV switchboards.

3. Thermal-Magnetic vs Electronic Trip Unit

Thermal-magnetic trip units are fixed-setting devices suitable for straightforward protection where the load characteristics are known and stable. Electronic trip units add adjustable protection settings (long-time, short-time, instantaneous, earth fault), real-time current monitoring, and communication interfaces for building management and SCADA integration. Both options are available across the EXM3 range — choose based on the application’s need for adjustability and data.

4. Where MCCB Fits in the Protection Hierarchy

In a typical power distribution system, MCB (Miniature Circuit Breaker) protects final circuits up to 63A. MCCB (Molded Case Circuit Breaker) handles branch circuits and sub-mains from 10A to 1250A — the EXM3 covers this range. ACB (Air Circuit Breaker) serves main incomers from 630A to 6300A, adding withdrawable rack-out capability and comprehensive communication features. For circuits that fall between MCB and ACB territory — where a standard MCB is too small but a full ACB is unnecessary — the EXM3 MCCB is the correct device.

Frequently Asked Questions

What is A MCCB circuit breaker?

A MCCB — Molded Case Circuit Breaker — is an overcurrent protection device with a robust moulded plastic case enclosing the contacts, arc chutes, and trip mechanism. It sits between miniature circuit breakers (MCBs) and air circuit breakers (ACBs) in the protection hierarchy, typically covering 10A to 1600A. MCCBs protect against overload and short circuit, and can include additional functions such as earth fault protection, undervoltage tripping, and motor operation. The EXM3 is an AC MCCB spanning 10A to 1250A with seven frame sizes and three performance levels.

What is the difference between MCCB vs MCB?

An MCB (Miniature Circuit Breaker) is a compact DIN-rail device typically rated up to 63A, used for final circuit protection in consumer units and distribution boards. An MCCB is larger, rated from 10A to 1600A, and built for higher fault currents in branch circuits and main incomers. Key differences: MCCBs have adjustable trip settings (with electronic trip units), higher breaking capacities (up to 100kA vs 6–10kA for MCBs), and a moulded case that can contain arc energy from larger faults. Use an MCB for a 32A lighting circuit; use an MCCB for a 400A feeder.

What’s the difference between MCCB and RCCB?

An MCCB protects against overcurrent (overload and short circuit). An RCCB protects against earth leakage (residual current). They serve different purposes and are often used together: the MCCB provides overcurrent protection while the RCCB detects earth faults. Some MCCBs can be equipped with an earth leakage module, combining both functions. The EXM3 is an MCCB; for earth leakage protection on the same circuit, pair it with an RCCB or specify the electronic trip unit version with integrated earth fault detection.

What is MCB, MCCB, and ACB?

These are three tiers of overcurrent protection devices, sized from smallest to largest. MCB (Miniature Circuit Breaker): DIN-rail mount, up to 63A, used for final circuits — lighting, sockets, individual appliances. MCCB (Molded Case Circuit Breaker): bolted or plug-in mount, 10A–1600A, used for branch circuits, feeders, and small main incomers. ACB (Air Circuit Breaker): open-frame construction, 630A–6300A, used for main switchboard incomers, often in withdrawable format. The EXM3 is an MCCB; HUYU’s EXW3 and HUW9 series are ACBs; the HUM and EXB series are MCBs.