DC MCB products play a vital role in solar electric systems. As an electrical protection device, DC MCBs are used to disconnect or connect circuits to protect solar systems from overloads, short circuits and other faults.

The working principle of DC MCB in PV system:

1.Overload Protection

Solar panels in a PV system convert sunlight into DC current. However, when the load in the system exceeds the rated current of the DC MCB, it can lead to an overload condition. In order to protect circuits and components from the hazards of overload, the DC MCB is able to detect this overload and quickly cut off the circuit, thus preventing excessive current from damaging the system.

2. Short circuit protection

Short circuit is another common fault in PV systems. A short circuit occurs when two conductors of a wire or cable come into direct contact. This situation causes an instantaneous increase in current to a very high level, which can lead to circuit failure and risk of fire. DC MCBs are able to detect short circuits and quickly cut off the circuit, preventing the current from continuing to flow, thus protecting the system and the environment in which it is used.

3. Quick cut-off

The DC MCB is designed with a quick cut-off so that the circuit can be shut down immediately when an overload or short circuit is detected. This fast cut-off capability prevents system damage and hazards associated with current overloads or short circuits, while minimising downtime and ensuring stable system operation.

4. High short-circuit tolerance

The currents in a PV system can be very high, especially in the event of a short circuit. DC MCBs have a high short circuit withstand capability that allows them to withstand high fault currents while keeping their functionality unaffected. This capability ensures the safe operation of the PV system in the event of a short circuit.

Onesto DC MCBs compliant with IEC60947-2 with the following product parameters:

▪Number of poles: optional 1P, 2P, 3P, 4P for different circuit configurations.

▪Rated voltage: optional 250V, 500V, 750V, 1000V DC voltage, applicable to different DC power systems.

▪Rated insulation voltage: 1000V, high insulation voltage can effectively isolate the circuit to ensure safe and reliable operation.

▪Rated impact withstand voltage: 6kV, able to withstand transient over-voltage in the circuit, ensuring that the equipment is not damaged by voltage spikes.

▪Rated short-circuit breaking capacity: 6kA, with high short-circuit withstand capacity, can quickly interrupt the circuit to prevent excessive current damage to equipment and wires.

These parameters are important:

▪Rated voltage: The DC voltage level is selected to match the rated voltage of the power system to ensure that Onesto DC MCBs will function properly and provide appropriate protection.

▪Rated Insulation Voltage: High insulation voltage reduces the risk of arcing and leakage currents and ensures safe isolation of circuits.

▪Impulse Withstand Voltage Rating: Onesto DC MCBs with high impulse withstand voltage capability can protect equipment from damage in the event of voltage spikes or disturbances in the circuit.

▪Short Circuit Interrupting Capability: Onesto DC MCBs with high short circuit interrupting capability can quickly cut off circuits, stopping high currents from flowing through equipment and wiring, preventing equipment damage or fire.

Onesto DC MCBs in Solar Power Systems:

■ Series and parallel connection of photovoltaic modules: In solar PV power systems, several photovoltaic modules need to be connected in series or parallel to provide the required voltage and current. In these circuits, Onesto DC MCBs are used as protection devices to ensure the safe operation of each module or cell series circuit.

■ Branch circuits: Onesto DC MCBs can be used to branch PV module circuits. When it is necessary to distribute the PV current to different target loads, Onesto DC MCBs can be used to create branches in the DC circuit and isolate and protect each branch individually.

■ Isolation Function: Onesto DC MCBs have an isolation function that allows for circuit isolation when specific circuits need to be maintained, serviced or troubleshot. By disconnecting the Onesto DC MCBs, it is possible to ensure that the equipment or power supply associated with that circuit is isolated from the mains supply for safe operation.

■ Protection: Onesto DC MCBs provide protection against overcurrents and short circuits in DC circuits. When the current abnormally exceeds its rating, Onesto DC MCBs quickly cut off the circuit, preventing damage to equipment or wiring and reducing the risk of fire and other safety risks.

DC MCBs play a key role in the interface with inverters, battery storage systems and the grid:

■ Inverter interface: the inverter converts the PV current to AC and connects it to the grid.Onesto DC MCBs are used to protect and isolate the DC circuit between the inverter and the PV modules, as well as the AC circuit at the output of the inverter. This ensures that the system is protected during inverter operation and also allows maintenance and servicing of the inverter at any time.

■ Battery storage system interfaces: In solar power systems, battery storage systems are used to store the electricity generated through the PV modules.Onesto DC MCBs provide isolation and protection between the battery system and the rest of the system. They ensure the reliable operation of the circuits between the battery system and the photovoltaic modules and inverters, and prevent the battery system from causing potential damage to other equipment.

■ Grid interface: Onesto DC MCBs also play an important role in solar power systems, ensuring a secure connection between the solar system and the grid. They are used to protect and isolate the circuits between the grid and the system, and can be disconnected from the grid when necessary, for example during maintenance or emergencies.

DC MCBs are essential components for ensuring the safety and efficiency of solar power systems. Onesto DC MCBs provide reliable electrical protection in various aspects of solar power systems.