Solar Circuit Breakers: The difference between DC and AC breakers

DC Circuit Breaker - Miniature Circuit Breakers for DC and Solar Generation

The JB is a DC circuit breaker dedicated to multi string photovoltaic installations.
This circuit breaker is designed to protect the cables located between each string of photovoltaic modules and the photovoltaic inverter against overloads and short circuits.
Combined with a switch , the JB will be installed in a string PV protection enclosure at the end of each string of photovoltaic modules.
It can be locked (by a padlocking device) in OFF position as a safety measure for removal of the PV inverter.
Since a fault current can flow in the reverse direction to the operating current, the JB can detect and protect against any bidirectional current.
To ensure the safety of the installation, it is necessary, depending on the various types of application, to combine the JB with:

a residual current device at the AC end

a fault passage detector (insulation monitoring device) at the DC end

an earth protection circuit breaker at the DC end


  • In all cases, fast action on site will be required to clear the fault (protection not ensured in the event of a double fault).
  • JB is not polarity sensitive: (+) and (-) wires can be inverted without any risk.

Meaning and Classification Models

DC Circuit Breaker

Main Characteristics

Operating Voltage (Ue) 1P=250 V DC, 2P=500 V DC
3P=750 V DC, 4P=1000 V DC
Rated insulation voltage (Ui) 1,000 VDC
Breaking capacity (Icu) 10 kA
Impulse voltage (Uimp) 4 kA
Electrical connection By the bottom for In and Out
Number of poles 1P, 2P, 3P, 4P
Standards IEC 60947-2
EN 60947-2

Technical Data

  • Position contact indication – suitability for isolation according to IEC/EN 60947-2 standard.
  • The presence of the green strip guarantees physical opening of the contacts and allows operations to be performed on the downstream circuit in complete safety.
  • Increased product service life thanks to fast closing independent of the speed of actuation of the toggle.
  • Pre-wired product: Input / Output on the same side.
Rated service breaking capacity (Ics) 100 % of the Icu
Endurance (O-C) Electrical 1,500 cycles (where L/R=2 ms)
Mechanical 20, 000 cycles
Mechanical 20, 000 cycles
Degree of pollution 2
Category A (no delay in accordance with IEC / EN 60947-2 standards)
Degree of protection
(IEC 60529)
Tropicalisation Relative humidity: 95 % at 55°C in accordance with
IEC 60068-2 and GB 14048.2 standards
Temperature Operating -25°C to 70 °C
Storage -40°C to 85°C


DC Circuit Breaker C curve

DC Circuit Breaker K curve

Instantaneous Trip

B Curve
These MCBs are suitable for cable protection.
Rating: 1-63A(30℃)
Instantaneous trip: (3-5)In
C Curve
Suitable Domestic and residential applications and electromagnetic starting loads with
medium starting currents.
Rating: 1-63A(30℃)
Instantaneous trip: (7-10)In
D Curve
Suitable for inductive and motor loads with high starting currents.
Rating: 1-63A(30℃)
Instantaneous trip: (10-14)In
K Curve
Suitable for inductive and motor loads with high inrush currents.
Rating: 1-63A(30℃)
Instantaneous trip: (14-18)In

Wiring Diagram

DC Circuit Breaker Diagrams


DC Circuit Breaker Installation

Dimensions (mm)

DC Circuit Breaker Dimensions

Weight (g)

Circuit breaker
Type 1P 2P 3P 4P
Weight (g) 120 240 360 480


DC Circuit Breaker Connection

AC Vs DC Circuit Breakers: The importance of the DC ARC Extinguisher


What is a DC Circuit Breaker?

DC Circuit Breaker offers reliable protection for DC electrical installations, safeguarding against overloads and short circuits. In the event of a fault, the circuit breaker automatically disconnects the electrical circuit, preventing wire damage and reducing the risk of fire. It also allows for manual opening under full-rated load during electrical maintenance.

The circuit breaker is designed for reversible connection, accommodating bidirectional current flow. Clear markings on the handle provide easy identification of the contact position. With a versatile design, it can be easily installed on both standard DIN rails and vertical surfaces.

Today’s DC circuit breakers have expanded applications including solar photovoltaics, electric vehicle charging stations, battery storage and UPS systems, as well as commercial and industrial DC distribution. Trust Langir’s DC Circuit Breaker for efficient and safe protection of your DC electrical systems.

What is the difference between circuit breakers and fuses?

  • Principle: Fuses use a wire that melts to break the circuit during overcurrent, while circuit breakers use a switch or trip mechanism.
  • Resetting: Fuses are one-time-use and need replacement, while circuit breakers can be manually or automatically reset.
  • Response Time: Fuses have a faster response time than circuit breakers.
  • Reusability: Fuses are disposable, while circuit breakers can be reused multiple times.
  • Sensitivity: Fuses are more sensitive to overcurrent, while circuit breakers have adjustable settings.
  • Application: Circuit breakers offer more flexibility and can protect against both overcurrent and short circuits.

What are the applications of Langir's DC Circuit Breaker?

  • Railway: DC circuit breakers are crucial for ensuring safety and reliability of power systems in railways. These breakers are capable of quickly detecting faults in circuits and cutting off the current to prevent damage to electrical equipment or potential fires. In railway systems, DC circuit breakers can also assist with controlling the operation and stopping of trains, as well as optimizing energy usage.
  • Power System: DC Circuit Breakers are essential for safe and reliable power systems, especially in solar energy. These breakers detect and isolate faults, protecting PV panels from overcurrent conditions and maximizing system efficiency. Langir’s DC Circuit Breaker (JB) can be applied to grounded or ungrounded systems and meets higher voltage and lower fault current levels of solar systems.
  • Home: DC Breakers are an essential safety feature for home electrical systems. These breakers protect against overcurrent conditions that can lead to electrical fires and equipment damage. In addition, they can help homeowners optimize energy usage by monitoring and controlling the flow of electricity.
  • Office Building: DC Breakers are commonly used in office buildings for a variety of applications, such as protecting electrical panels and equipment, controlling lighting and HVAC systems, and managing emergency power systems. They are also a crucial component of renewable energy systems, such as solar panels and wind turbines.

How to choose suitable dc circuit breakers?

  • Voltage Rating: Determine the maximum voltage of your DC system. Ensure that the circuit breaker’s voltage rating matches or exceeds your system voltage to ensure proper protection.
  • Current Rating: Identify the maximum current that your DC circuit can handle. Choose a circuit breaker with a current rating that matches or exceeds the maximum current of your system.
  • Trip Curve: Consider the desired trip curve, which determines how quickly the circuit breaker will trip in response to an overload or short circuit. Different applications may require different trip curves based on the level of protection needed.
  • Breaking Capacity: Evaluate the breaking capacity or interrupting rating of the circuit breaker. It indicates the maximum fault current that the breaker can safely interrupt without damage. Ensure that the breaking capacity meets or exceeds the fault current of your DC system.
  • Mounting Type: Determine the suitable mounting type for your application. DC circuit breakers are commonly available in panel-mount, DIN rail-mount, or surface-mount configurations. Choose the one that fits your installation requirements.
  • Additional Features: Consider any additional features that may be required for your specific application, such as auxiliary contacts, remote tripping capabilities, or status indicators.
  • Compliance and Certifications: Verify that the chosen circuit breaker complies with relevant industry standards and certifications to ensure safety and reliability.
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