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PEBS-H-175
PEBS-H-125
PEBS-H-63
PEBS-H-50
PEBS-S-80 (UL)
PEBS-L-175
PEBS-L-125
PEBS-L-125 (UL1077)
PEBS-L-63
MCB Weatherproof Enclosure (PEBS Series)
DC MCCB (PEMC Series)
PEDS (1500V,16~55A) Series
PEDS-H-R/F (1500V,16~55A) Series
PEDS-H (1500V;40A,50A) Series
PEDS-EL (16~55A) / PEDSC-EL (32A)
PEDSC (1000V&1200V;32A) Series
Remote Tripping Isolator (PERD-100/100T series)
DC Combiner Box (PEJB Series)
AC Combiner Box (PEDB Series)
DC&AC Combiner Box (PEJDB Series)
Intelligent PV Combiner Box (PEJB Series)
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Molded Case Circuit Breaker (MCCB) Selection Guide: PROJOY PEMC Series
Electrical safety depends on reliable protection against overloads and short circuits, especially in industrial power distribution, solar PV and energy storage systems. A molded case circuit breaker (MCCB) automatically disconnects a circuit when an overload or short circuit occurs, helping prevent equipment damage, system downtime and fire hazards. This guide explains the differences between MCBs and MCCBs, the main types of AC and DC MCCBs, their applications, and how to select the right PROJOY PEMC Series MCCB for a specific system.
What Is an MCCB and Why Do C&I Energy Storage Systems Need It?
A molded case circuit breaker (MCCB) automatically interrupts a circuit during an overload or short circuit. Compared with conventional power distribution systems, commercial and industrial (C&I) energy storage systems operate under more demanding conditions:
PROJOY PEMC Series: AC and DC MCCBs
The PROJOY PEMC Series includes AC and DC MCCBs designed for different voltage levels, current ratings and application requirements.
AC Molded Case Circuit Breakers
PEMC-AC400V
16-630 A, AC 400/690 V
Standard AC MCCB series for overload and short-circuit protection in power distribution systems.
PEMC-AC800V
63-800 A, AC 800/1000/1140 V
High-voltage AC MCCB series designed for demanding power distribution applications.
DC Molded Case Circuit Breakers
PEMC-250/320/400/630/800
63–800 A, DC 1000/1500 V
High-voltage version with TÜV and CE certifications.
PEMC-250
100–250 A, DC 125/250 V
Low-voltage version.
PEMC-320ZH, PEMC-500ZH, PEMC-400DH, PEMC-630DH, PEMC-630DR
50-630 A, DC 250–2000 V
Standard version designed for PV combiner box applications.
PEMC-320ZH, PEMC-500ZH, PEMC-400DH, PEMC-630DH (H)
63-630 A, Up to DC 1500 V
BESS version engineered for demanding battery energy storage applications.
How to Select the Right MCCB: Key Factors to Consider
Voltage and Current Ratings
Rated operational voltage (Ue): The Ue rating must not be lower than the system’s maximum operating voltage.
Rated current (In): The In rating must exceed the calculated load current. Also check the frame size rating, as it determines the breaker size and the maximum compatible trip-unit rating.
Breaking Capacity
Icu: The maximum short-circuit current that the MCCB can interrupt. The Icu rating must exceed the prospective fault current.
Ics: The short-circuit current that the MCCB can interrupt while remaining suitable for continued service. Ics = 100% Icu indicates high reliability and is suitable for applications requiring service continuity.
Trip Unit Type
Thermomagnetic trip: Combines overload and short-circuit protection. It is cost-effective and suitable for most conventional power distribution systems.
Electronic trip: Offers adjustable current and time settings. It provides precise, flexible and selective protection for systems with higher control requirements.
Key Accessories
Auxiliary and alarm contacts: Provide remote indication of the MCCB’s open, closed or tripped status.
Shunt and undervoltage releases: A shunt release enables remote tripping. An undervoltage release trips the MCCB when the circuit voltage falls below a specified level.
Installation and Safety
Arcing distance: An arc may be released through the arc vent when the MCCB interrupts a high current. Allow sufficient installation clearance. For compact panels, select a short-arcing or zero-external-arcing model.
Environmental suitability: Check the operating temperature and altitude ratings. For demanding environments, select an MCCB designed for a wide temperature range and stable high-altitude operation.
MCCB Selection Example for a 1500V DC PV System
This case examines the selection of a DC input-side protection circuit breaker for a string inverter specified by an engineering design institute. The breaker is intended for the output circuit of a PV combiner box or an integrated DC protection unit within the inverter. It serves as a critical DC-side protection device in the PV power generation system.
System Parameters
System voltage: DC 1500 V
Maximum operating current: 240 A per circuit
Prospective short-circuit current: 20 kA
Key Requirements
Reliable breaking: Safely interrupt DC short-circuit current.
Compact design: Fit within a high-density electrical enclosure.
Inrush withstand: Prevent nuisance tripping during closing.
MCCB Rating Selection
Rated operational voltage (Ue): Ue ≥ DC 1500 V. This is required for adequate insulation and reliable arc interruption.
Ultimate breaking capacity (Icu): Prospective short-circuit current = 20 kA. Select a DC 1500 V MCCB with Icu ≥ 20 kA.
Rated current (In): Maximum operating current = 240 A. After considering temperature, altitude derating and operating margin, select a trip unit rated at In = 320 A.
Recommended MCCB Model
MCCB Applications in Energy Storage and Solar PV Systems
Large-Scale Battery Energy Storage Systems
DC MCCBs protect battery clusters during charging and discharging. Their non-polarized design supports bidirectional current flow and helps prevent battery damage caused by overloads and short circuits.
Solar PV Systems
MCCBs are widely used in DC distribution cabinets and PV combiner boxes at utility-scale solar power plants. They provide reliable overload and short-circuit protection for safe and stable power generation.
Commercial and Industrial PV-Storage Systems
MCCBs protect key equipment such as battery packs, inverters and combiner boxes. They improve system reliability, reduce equipment failures and support efficient energy use.
Frequently Asked Questions
What Is an MCCB and How Does It Work?
An MCCB is a protective switching device used to protect electrical circuits from overloads and short circuits. When the current exceeds the set limit, its trip unit triggers the operating mechanism and automatically opens the circuit.
MCB vs MCCB: What Is the Difference?
An MCB is generally used for lower-current circuits with fixed trip characteristics. An MCCB supports higher current ratings and breaking capacities, with more trip-unit and accessory options for industrial applications.
What Is the Difference Between an AC MCCB and a DC MCCB?
An AC MCCB protects AC circuits, where natural zero-crossing helps extinguish the arc. A DC MCCB uses a dedicated arc-extinguishing design because DC has no natural zero-crossing.
How Do You Choose the Right Molded Case Circuit Breaker?
Confirm the circuit type, system voltage, load current and prospective short-circuit current. Select the correct number of poles and trip unit. Ensure that Ue ≥ system voltage and Icu ≥ prospective fault current. Select In according to the load current, conductor capacity and applicable derating factors.
Where Are MCCBs Commonly Used?
MCCBs are used in industrial power distribution, solar PV systems, battery energy storage systems and PV-storage systems. Typical installation points include battery clusters, inverters, DC distribution cabinets and PV combiner boxes.
What Should You Check When an MCCB Trips?
Check for overloads, short circuits, loose connections and abnormal temperatures. Also verify the trip settings and load current. Do not reset the MCCB until the cause of the trip has been identified and corrected.
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