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What is a DC isolator？

A DC isolator is a safety device that is used to disconnect a direct current circuit and is commonly applied in photovoltaic systems. Its main function is to safely disconnect the electrical connection between solar panels and the inverter during maintenance, fault handling, or emergency situations.

Unlike standard switches, a DC isolator is specifically designed for direct current applications, which allows it to handle higher voltage levels and arc risks, thereby ensuring safer operation. In a photovoltaic system, it is usually installed between the solar modules and the inverter, which helps maintain system safety.

How the built in DC isolator in an inverter works？

The inverter’s built-in DC isolator is an integrated switching device with the same working principle as an external isolator, but in a more compact design.

During normal operation, it stays closed to let PV DC current pass into the inverter. For maintenance or emergencies, it can be manually switched off to disconnect the PV array from the inverter.

It uses arc-resistant structures to quickly break the circuit and suppress DC arcs. Some advanced models also support automatic disconnection under faults or overvoltage for better safety.

As it is integrated inside the inverter, it simplifies wiring and installation, and reduces failure risks from rain, dust and other environmental factors.

Is an additional DC isolator still required?

Regulations and standards

Whether an additional DC isolator is required depends first on local electrical regulations and industry standards. In some regions, external DC isolators were once mandatory, while in recent years, certain areas have relaxed these requirements and allow the use of only the built in isolator in the inverter.

Therefore, the latest regulations should be checked before system design and installation so that compliance issues can be avoided.

Inverter installation location and accessibility

The location of the inverter affects whether an additional isolator is needed. If the inverter is installed in an easily accessible place such as on the ground, in a garage, or on an indoor wall, the built in isolator is usually sufficient for daily operation and emergency shutdown.

If the inverter is installed on a roof or in a location that is difficult to access, an external DC isolator can provide a more convenient and safer way to disconnect power.

Safety and emergency needs

From a safety perspective, an external DC isolator provides an additional point of disconnection. In situations such as fire, electrical faults, or urgent maintenance, power can be cut off quickly without approaching the inverter, which can be beneficial in certain scenarios.

If the system is properly designed and the inverter is reliable with adequate protection functions, relying on the built in isolator is generally acceptable in many cases.

Maintenance and service convenience

During system maintenance, a DC isolator plays a significant part. An external isolator allows technicians to disconnect power before accessing the system, which improves maintenance efficiency and reduces risk.

It also provides flexibility when different parts of the system need to be tested separately. At the same time, adding external components increases system complexity and requires additional inspection and upkeep.

What are the functions of internal and external DC isolators?

If required, how to choose a high quality DC isolator?

Rated voltage and current

When selecting a DC isolator, its rated voltage and current should be higher than the actual system values. Common voltage ratings include 600V, 1000V, and 1500V DC, while current ratings include 16A, 32A, and 40A.

Since DC arcs are harder to interrupt, insufficient ratings can lead to safety risks, so the isolator rating should be equal to or greater than the maximum system voltage and current.

Certification and standards

High quality DC isolators should comply with international or local standards such as IEC 60947 3, UL, CE, or TUV. These certifications indicate that the product has passed strict testing for safety, durability, and arc performance.

Products with multiple certifications are generally more reliable and easier to approve during project inspection.

Protection level

If the isolator is installed outdoors, its protection level is highly relevant. Products with IP65 or IP66 ratings are recommended, as they provide strong resistance to water and dust. Resistance to ultraviolet exposure should also be considered, as long term sunlight can cause material aging and affect performance.

Arc extinguishing capability

The main difference between a DC isolator and a standard switch lies in its arc control capability. Since direct current does not have a natural zero crossing point, arcs are harder to extinguish, so specialized designs such as rapid contact separation, magnetic blowout, or special contact materials are used. The product should be specifically designed for DC applications rather than adapted from standard switches.

Conclusion

Whether an additional DC isolator is required depends on local regulations, system design, and installation conditions. Regardless of the chosen approach, ensuring that equipment meets standards, is properly installed, and offers reliable performance is the foundation for safe photovoltaic system operation.

When choosing a high-quality DC isolator, KRIPAL’s UKPD32 series or UKGD63 series are specifically engineered for PV systems. With IP66 ratings and less than 3ms arc extinguishing time, they exceed standard safety requirements.

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