A molded case circuit breaker (MCCB) is one of the most widely used protective devices in industrial and commercial power distribution. If you're sourcing MCCBs for a switchgear panel, motor control center (MCC), or distribution board, this guide covers everything you need to make the right choice.
What Is a Molded Case Circuit Breaker?
A molded case circuit breaker is a low voltage protective switching device housed in a molded insulating case. It automatically interrupts current when it detects an overload or short circuit, protecting cables, equipment, and personnel from damage.
MCCBs cover a current range of 16A to 1600A — bridging the gap between miniature circuit breakers (MCBs, up to 125A) and air circuit breakers (ACBs, from 630A upward). They are the standard choice for industrial feeder protection, motor branch circuits, and main distribution panels.
Types of Molded Case Circuit Breakers
By Trip Unit
- Thermal-Magnetic MCCB — Uses a bimetallic strip for overload protection and an electromagnetic coil for short-circuit protection. Simple, reliable, cost-effective. Best for standard applications where fixed protection settings are acceptable.
- Electronic Trip Unit MCCB — Microprocessor-based with fully adjustable protection settings: overload threshold (Ir), short-circuit threshold (Isd), time delays, and ground fault protection. Offers data logging, communication interfaces, and higher precision. Recommended for intelligent switchgear and SCADA-integrated systems.
By Mounting Type
- Fixed — Permanently mounted. Most common and cost-effective.
- Plug-in — Removable without disconnecting wiring. Easier maintenance.
- Draw-out (Withdrawable) — Fully withdrawable for maintenance without de-energizing adjacent circuits. Required for critical feeders.
By Number of Poles
- 3-pole (3P) — For three-phase systems (most industrial applications)
- 4-pole (4P) — For three-phase + neutral systems, or where neutral protection is required
Key Ratings to Understand
Rated Current (In)
The maximum continuous current the MCCB can carry without tripping. Common ratings: 16A, 32A, 63A, 100A, 160A, 250A, 400A, 630A, 800A, 1000A, 1250A, 1600A.
Selection rule: Choose In ≥ 125% of maximum load current to allow for motor startup surges and future load growth.
Breaking Capacity (Icu)
The maximum short-circuit current the MCCB can safely interrupt. This is critical — if fault current exceeds Icu, the breaker can fail catastrophically.
- Standard industrial applications: 36kA – 50kA
- Near transformers or substations (high fault current): 65kA – 100kA
Always verify the prospective short-circuit current (PSCC) at the installation point before selecting an MCCB.
Rated Voltage (Ue)
Most industrial MCCBs are rated for 400V / 690V AC. Verify the system voltage matches the MCCB's rated voltage — using an MCCB below its rated voltage reduces breaking capacity.
MCCB vs MCB vs ACB
| Parameter | MCB | MCCB | ACB |
|---|---|---|---|
| Current Range | Up to 125A | 16A – 1600A | 630A – 6300A |
| Breaking Capacity | Up to 25kA | Up to 100kA | Up to 100kA |
| Trip Unit | Thermal-magnetic | Thermal-magnetic or Electronic | Electronic |
| Application | Residential, light commercial | Industrial, commercial | Main distribution, large industrial |
| Communication | No | Optional | Standard |
IEC Standards for MCCBs
When evaluating an MCCB supplier, verify compliance with:
- IEC 60947-2 — Primary international standard for low-voltage circuit breakers
- GB 14048.2 — China national standard (equivalent to IEC 60947-2)
- CE marking — Required for products sold in the EU
- CCC certification — China Compulsory Certification for the domestic market
Always request type test reports from an accredited third-party laboratory (KEMA, TÜV, SGS) when qualifying a new supplier.
Practical MCCB Selection Checklist
- ✅ Determine maximum load current → select In ≥ 125% of load current
- ✅ Calculate PSCC at installation point → select Icu above this value
- ✅ Confirm system voltage (400V or 690V)
- ✅ Choose trip unit type: thermal-magnetic (standard) or electronic (intelligent systems)
- ✅ Select number of poles: 3P or 4P
- ✅ Decide mounting type: fixed, plug-in, or draw-out
- ✅ Check communication requirements: RS485/Modbus for SCADA integration
- ✅ Verify IEC 60947-2 type test reports from supplier
Wanlong Electric MCCB Range
Wanlong Electric manufactures a complete range of intelligent molded case circuit breakers for industrial buyers, panel builders, and EPC contractors worldwide.
- 📋 Current range: 32A to 1600A
- 🔧 Trip units: Thermal-magnetic and electronic (with adjustable Ir, Isd, Ii, Ig)
- 🔌 Communication: RS485 / Modbus RTU for SCADA integration
- ✅ Certifications: IEC 60947-2 / GB 14048.2, CE, CCC
- 📦 OEM/ODM: Custom branding, ratings, and configurations available
- 🚚 Delivery: Standard orders ship within 7 days from Suzhou, China
Need a datasheet, type test report, or factory-direct quote? Contact Wanlong Electric — our engineering team responds within 24 hours.
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