What is the DC miniature circuit breaker(MCB)?


1. DC Breaker vs AC Breaker
2. DC Isolator vs DC Breaker
3. Product Details
4. Advantages
 4.1 Dimensions
 4.2 Two-stage spring buckle for fast installation
 4.3 Side Heat Strip
 4.4 Various Types and Rated Voltage
 4.5 Reliable and Safety
 4.6 Mark Clearly
5. Sizing Tips
 5.1 DC circuit breaker sizing calculator
 5.2 DC breaker for battery, controllers, inverters and DC equipment
 5.3DC breaker for solar
6. Connection
7. Application
8. DC MCCB / DC Molded Case Circuit Breaker

DC Breaker vs AC Breaker

The functions of DC MCB and AC MCB are the same. They both protect electrical appliances and other load equipment from overload and short-circuit problems, and protect the circuit. But the usage scenarios of AC MCB and DC MCB are different. It generally depends on whether the voltage used is alternating current states or direct current states. Most of the DC MCB uses some direct current systems like new energy, solar PV, etc. The voltage states of DC MCB are generally from DC 12V-1000V.

USFULL DC breakers use fireproof shells, which can stand high voltage and severe environments. Most solar projects will be put in the desert and wild areas hence we will offer you reliable products to keep good performance in such usage.

The USFULL DC Miniature Circuit Breaker/ DC MCB for solar is equipped with both a thermal and a magnetic tripping mechanism to protect DC electrical installations of solar and battery from overloads and short circuits. When a fault is detected, the circuit breaker automatically shuts down the electrical circuit to prevent wire damage and fire and also provide safety for your electrical installation. When performing electrical maintenance, the circuit breaker can also be manually opened whilst the full-rated load is flowing without causing any damage. The circuit breaker is designed for a reversible DC breaker connection and can be wired in either direction. It operates on a bidirectional current. The built-in indicator window allows you to quickly determine the contact position of the circuit breaker. The buckle design allows for simple installation on standard din rails, and provide easiness for DC breaker connection installation.

DC Breaker vs AC Breaker

DC isolator and DC circuit breaker differ depending on many factors such as the method of operation, device type, function, operation, current path, and trapped charge. Let’s discuss these factors in detail. The basic differences between circuit breakers and isolators include:

  • DC isolator cannot disconnect a load or create a fault while a circuit breaker is designed to do so.
  • A circuit breaker must always be operated in advance, as the disconnector is always operated after the circuit breaker. 

Product Details

The USFULL DC Miniature Circuit Breaker is equipped with both a thermal and a magnetic tripping mechanism and has certification from CE and IEC standards.
The rated current of the USFULL DC MCB for solar is clear hence it is easy to read. For example, this picture shows the DC mini circuit breaker for 63 A (63 Amp DC breaker).

The DC mini circuit breaker is available in various operating voltage starting from:

  • 12V DC breaker
  • 24V DC circuit breaker
  • 48V DC circuit breaker
  • 250 VDC / 300 VDC circuit breaker
  • 500 VDC / 600 VDC circuit breaker
  • 750 VDC / 900 VDC circuit breaker
  • 1000 VDC / 1200 VDC circuit breaker

The USFULL DC Miniature Circuit Breaker also has a built-in indicator window that aids in determining the contact position.

For 2P to 4P DC miniature circuit breakers, they are equipped with an invisible shorting bar and screw hole plug. Hence provide neat installation and safety from accidental disassembly after installation.

The contact material is from silver and electromagnetic coils and conductive parts are made of materials containing more than 99.5%, copper good conductivity, low temperature rises, and low resistance.

FMB7 Series Circuit BreakerFMB7N-63PV
Frame Degree Rated Current63A
Pole1P, 2P, 3P, 4P
Rated Operating Voltage (VDC)12V, 24V, 48V, 300V, 600V, 900V, 1200V
Rated Current In (A)10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A
Rated Insulation Voltage Ui (VDC)1250VDC
Rated Impact Voltage Uimp (kV)6
Ultimate Breaking Capacity Icu (kA)6
Run Breaking Capacity Ics (%Icu)100
Curve TypeC
Trip TypeThermal-Magnetic
MechanicalActual average value20000 times
Standard value8500 times
ElectricalActual average value2500 times
Standard value1500 times
Wiring Capacity (mm²)In≤32A, 1.5~6mm²; In ≥40A, 10~16mm²
Ambient Temperature (℃)-20℃~+70℃
Altitude≤2000 m
Relative Humidity≤9.5%
Pollution Level2, 3
Installation EnvironmentNo obvious shock and vibration
Installation CategoryClass II, Class III
InstallationStandard din rail
Dimensions (W)*(H)*(D) (mm)W18365472
Weight (KG)


The USFULL DC circuit breakers are suitable for DC breaker for solar and DC breaker for battery installation and have many advantages as follows:


The USFULL DC circuit breaker provides ample terminal heightening size, providing better creepage distance and better arc isolation.

Two-stage spring buckle for fast installation

It is easy to install and uninstall the product because it has a halfway stop function. Buckle design for easy mounting on standard din rails. Install by snapping it into the slot and pressing the bottom until the buckle clicks into the din rail.

Side Heat Strip

The USFULL DC circuit breaker for solar and DC circuit breaker battery provides a sides heat strip and flame-retardant shell, improving the air circulation between multi poles products that are installed inside the DC breaker panel box. Hence the USFULL DC MCB for solar is suitable for use in various high temperature environments.

Various Types and Rated Voltage

The USFULL DC breakers are available in various rated voltage hence it is suitable to protect DC connection for battery, solar, panel, and DC breaker box. It is available in 300V/600V/900V/1200V rated voltage.

The USFULL DC breakers are also available in single and multi poles 1P 2P 3P 4P, wide range of Ampere 10A-63A, and have a 6kA breaking capacity.

Reliable and Safety

The USFULL DC breaker for solar has certification from CE, IEC, TUV, and ISO and comply with IEC and GB standard. DC breaker solar is equipped with both a thermal and a magnetic tripping mechanism for reliability and safety.

Mark Clearly

A built-in indicator window helps to locate the contact location and to visualize the status of the contact position.

Sizing Tips

DC circuit breaker sizing calculator

Tips for choosing the appropriate circuit breaker DC breaker for a battery for diverse circumstances.

DC breaker for battery, controllers, inverters and DC equipment

  • Determine maximum continuous current = Watt/Voltage
  • Maximum current = 1.25 * maximum continuous current operating current
  • Select the circuit breaker whose rated current is greater than and closest to the maximum calculated current

DC breaker for solar

  • Determine the short-circuit current
  • Maximum current = Short-circuit current * 1.56
  • Select the circuit breaker whose rated current is greater than and closest to the maximum current


Connected on positive and negative.

The USFULL DC miniature circuit breakers provide easy installation in the DC breaker box because there is no distinction between positive and negative poles so don’t worry about a faulty DC breaker connection.


The USFULL DC miniature circuit breakers are suitable for DC breaker for home solar lighting installation, DC breaker for solar photovoltaic power generation project, DC breaker for battery photovoltaic energy storage, DC breaker for the photovoltaic irrigation project, and also DC breaker for rail transit and electric locomotive/ship.

DC MCCB / DC Molded Case Circuit Breaker

The USFULL also has MCCB Molded Case Circuit Breaker, current ratings available from 63, 80, 100, 120, 140, 160, 180, 200, 250, 300, 320, 350, 400, 500, 630, 700, 800 amps.

Rated voltage DC500V, DC1000V, DC1500V.

2P 500V 4P 1000V breaking capacity is 1.5-2.0kA.

TypeFMM1-PV- 125FMM1-PV-250FMM1-PV-400FMM1-PV-630
Pole2P, 4P
Max. Rated Current125A250A400A630A
Rated Current In (A)16/20/25/32/40/50 /63/80/100/125100/125/150/200 /225/250250/300/350/400400/500/630
Rated Working Voltage Ue (VDC)500V, 1000V
Rated Insulated Voltage Ui (V)1500V
Rated Impulse Withstand Voltage8 kV
Short-Circuit Breaking Capacity (kA) Icu (Ics=75% Icu)500V25353535
Isolator CapacityYes
Operating Temperature-25℃~+50℃
Protection GradeIP20
Flashover Distance≥ 50
Instantaneous Action Value10ln±10%
Installation MethodFixed type
Technical StandardIEC60947-2, IEC60947-1, GB14048.1, GB14048.2

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USFULL specializes in solar pumping inverter and variable frequency drive. The product technology research and development is constantly updated. The shell design is patented. We only make products that make customers happy.

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