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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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DC Miniature Circuit Breaker (MCB) Selection Guide: PROJOY PEBS Series
A DC miniature circuit breaker (MCB) protects circuits against overloads and short circuits in solar PV, battery energy storage and DC distribution systems. Selecting the right breaker requires careful consideration of system voltage, rated current, breaking capacity and operating conditions.
Designed for energy storage and other DC applications, PROJOY PEBS series DC MCBs combine thermal-magnetic protection with a range of voltage, current and breaking capacity ratings to suit different system requirements. The series also offers non-polarized designs and optional accessories for flexible installation and system integration. This MCB selection guide explains the key selection criteria, compares PROJOY PEBS models and provides a practical battery storage selection example.
What Is a DC MCB and How Does It Work?
A DC MCB (miniature circuit breaker) is a protective device that automatically interrupts a DC circuit during an overload or short circuit, helping protect wiring and connected equipment. Used in solar PV, battery energy storage and DC distribution systems, thermal-magnetic DC MCBs combine two tripping mechanisms with an arc-extinguishing system to interrupt fault currents.
Overload Protection: Thermal Tripping
When excessive current flows for a sustained period, a bimetal strip heats up and bends, triggering the trip mechanism to open the contacts. This delayed response allows brief current increases while protecting against prolonged overloads.
Short-Circuit Protection: Magnetic Tripping
A short circuit causes a rapid surge in current. The resulting magnetic field in the electromagnetic coil moves a plunger, releasing the trip mechanism and quickly separating the contacts.
Arc Extinction: Interrupting DC Current
As the contacts separate, an electrical arc can form. The arc is directed into an arc chute, where it is divided, cooled and extinguished. This is particularly important in DC circuits because the current has no natural zero crossing to help extinguish the arc.
Manual Operation and Reset
A DC MCB can be manually switched ON or OFF using its handle. After a trip, it can be reset once the fault has been cleared and the breaker is confirmed fit for service. Unlike a fuse, it does not normally require replacement after operating.
PROJOY PEBS Series DC MCBs: Models and Specifications
Battery energy storage systems range from residential installations to commercial, industrial and utility-scale projects. Each requires reliable circuit protection, rapid fault interruption and effective arc extinction. Selecting a suitable DC miniature circuit breaker involves matching its voltage rating, rated current and breaking capacity to the requirements of the circuit.
PROJOY PEBS Series DC MCBs include models for higher-voltage and lower-voltage DC systems, as well as enclosed options for installations requiring additional environmental protection. Across the range, available ratings span 80–1500 V DC and 2–175 A. For applications exceeding the capabilities of a DC MCB, PROJOY also offers PEMC series DC molded case circuit breakers.
Models for High-Voltage DC Systems
Models for Low-Voltage DC Systems
DC MCBs in Weatherproof Enclosures
How to Select the Right DC MCB: 6 Key Checks
Rated DC Voltage
MCB rated voltage ≥ Maximum system voltage
For solar PV, account for cold-weather open-circuit voltage; for battery storage, check the maximum charging voltage.
Rated Current
Load current ≤ MCB rated current ≤ Cable current-carrying capacity
Account for temperature derating and installation conditions when sizing the DC MCB.
Short-Circuit Breaking Capacity
Breaking capacity ≥ Maximum prospective short-circuit current
Check the rating at the required DC voltage and pole configuration.
Tripping Curve
Select a B- or C-curve DC MCB to accommodate normal current transients and ensure fault protection. Refer to the model’s DC tripping curve.
Poles and Polarity
Match the pole configuration to the system voltage and wiring requirements. Check whether the DC circuit breaker is polarized or non-polarized.
Installation and Certifications
Verify temperature limits, enclosure IP rating, mounting requirements and the certifications required for your application.
DC MCB Selection Example: A Battery Storage System
This example explains how to select a DC miniature circuit breaker for the high-voltage box of a battery storage system. The process covers battery string voltage, operating current, short-circuit breaking capacity, tripping characteristics and installation conditions.
Battery String Requirements
- Energy capacity: ≥78.3 kWh
- Minimum voltage: Umin ≥480 V DC
- Maximum voltage: Umax ≤522 V DC
- Charge and discharge rate: 0.5C
Battery Module Parameters
- Nominal voltage: 51.2 V DC
- Voltage range: 48.2–52.2 V DC
- Nominal energy: 7.83 kWh
- Nominal capacity: 150 Ah
- Continuous charge and discharge rate: ≤1C
- Internal resistance: ≤6 mΩ
Ten battery modules are connected in series to form one battery string.
- Stated energy: 10 * 7.83 = 78.3 kWh
- Minimum voltage (Umin): 10 * 48.2 = 482V < 600V
- Maximum voltage (Umax): 10 * 52.2 = 522V < 600V
- Charge and discharge rate: 1C > 0.5C
PROJOY DC MCB Selection
Parameter Calculations
- Maximum battery string terminal voltage: Umax = 522 V DC
- Battery string rated current: Ie ≥ 0.5C = 0.5 * 150 = 75 A
- Short-circuit current calculation at the battery terminals: IDK = 522 V / (10 * 6 * 10 - 3) = 8.7 kA
- Circuit breaker short-circuit breaking capacity: Icu ≥ IDK = 10 kA
Circuit Breaker Specification Selection
Based on the electrical calculations above, the following circuit breaker specifications are initially selected:
- Ue = 600 V DC
- In = 75 A * 1.25 = 97.3 A ≈ 100 A
- Icu = 10 kA
- Circuit breaker long-time current setting: IDZ1 = 130 A
Tripping Curve Selection
- For a B-curve trip characteristic: kn = (4~7)
Reliable tripping check: IDK = 8.7 kA ≥ kn * In = 7 * 100 = 700
Sensitivity check: KL = IDK / (7 * 100) = 8.7 kA / 700 = 12.4 > 1.2
- For a C-curve trip characteristic: kn = (5~10)
Therefore, a circuit breaker with a B-curve trip characteristic should be selected.
Temperature Calibration
Energy storage applications have specific operating temperature conditions. Charging and discharging involve chemical reactions within the battery string, and its controlled ambient temperature is generally 40–55°C.
Therefore, select a circuit breaker calibrated at 50°C based on the temperature inside the battery pack.
Wiring and Installation
AC current has natural zero crossings, whereas DC current does not. Consequently, AC and DC circuit breakers differ in how they extinguish arcs. DC circuit breakers are generally polarized and must be wired according to their polarity markings.
PROJOY MCBs feature a non-polarized design. In battery charging circuits, the DC circuit breaker does not require polarity-specific wiring relative to the PCS “+” and “−” terminals, simplifying installation and use.
Conclusion
Based on the analysis and calculations above, select a circuit breaker with the following specifications:
Rated voltage: Un = 600 V DC; Rated current: In = 100 A; Short-circuit breaking capacity: Icu = 10 kA;
Tripping curve: B curve; Reference calibration temperature: 50°C
👉 PROJOY 600 V DC, 2-pole circuit breaker, such as the PEBS-H-175
Why Choose PROJOY PEBS Series DC MCBs?
Choosing the right circuit breaker is essential to the safe operation of an energy storage system. PROJOY PEBS series miniature circuit breakers are designed for energy storage applications, combining advanced technology, application flexibility and reliable quality.
01
A non-polarized design simplifies installation, while advances in DC arc extinction enhance circuit protection.
02
Options for low- and high-voltage systems, as well as low- and high-current circuits, meet diverse application needs.
03
Mechanical endurance of at least 15,000 operations and breaking capacity up to 10 kA.
04
TÜV, CE, CB, UL, SAA and RCM.
05
Supports add-on accessories, including auxiliary contacts and shunt releases.
06
A large contact gap helps protect downstream circuits and equipment from electrical hazards.
Frequently Asked Questions About Miniature Circuit Breaker
A DC MCB protects circuits against overloads and short circuits. Thermal tripping responds to sustained overloads, while magnetic tripping responds to high short-circuit currents. The handle also allows manual switching.
Yes. Once the fault has been cleared and the breaker is confirmed fit for service, it can be manually reset. Do not repeatedly reset an MCB without identifying the cause of the trip.
A non-polarized DC MCB is designed to interrupt current flowing in either direction, making it useful for battery charging and discharging circuits.
The main difference is arc interruption. AC current naturally crosses zero, helping extinguish the arc. DC current has no natural zero crossing, so DC circuit breakers require suitable arc-extinguishing designs and DC voltage ratings.
Both protect against overcurrent. An MCB trips and can usually be reset, while a fuse melts to interrupt the circuit and must be replaced.
A miniature circuit breaker (MCB) typically provides compact protection for lower-current circuits. A molded case circuit breaker (MCCB) generally offers higher current ratings, higher breaking capacities and more trip-setting options, depending on the model.
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