EXU3DC-II+III – Type 2+3 DC SPD 800V-1200V

The HUYU EXU3DC-II+III T2+T3 DC SPD combines Type 2 and Type 3 surge protection in a small plug-in module!

The EXU3DC-II+III series of T2+T3 DC SPDs are manufactured by HUYU Electric and provide combined surge protection against over voltage transients created by lightning strikes and switching surges from Type 2 and Type 3 SPD devices in one compact plug-in module unit!

These T2+T3 DC SPDs have been designed specifically for use with DC power systems, including photovoltaic installations, battery energy storage, and electric vehicle charging infrastructures. The maximum continuous voltage ratings are 800V, 1000V, and 1200V DC, with a maximum discharge capacity of 40kA at each voltage rated level, which means that these two-stage DC surge protection devices are designed to handle the energy levels produced during lightning strikes, as well as switching surges that could otherwise cause damage to sensitive power electronics downstream.

Due to the incorporation of both the T2 and T3 surge protection devices, the EXU3DC-II+III module has the ability to protect against both high-energy transients via the Type 2 device, while also protecting against low voltage transients via the Type 3 device, thus eliminating multiple SPDs required in a single DC distribution system. This innovative modular design has been coupled with a replaceable plug-in design that also features a visual fault indicator and remote signaling contact for easy maintenance!

In addition, HUYU’s EXU3DC-II+III T2+T3 DC SPD has been certified by IEC 61643-1 and carries CE, TUV, and CQC approvals, making it an ideal choice for all of your DC surge protection needs in EV charging, energy storage, and solar applications because this device has been manufactured according to international safety standards. HUYU Electric provides factory direct OEM and ODM support along with full documentation.

Technical Data

Where T2+T3 Protection Makes the Difference

A standalone Type 2 DC surge protector handles the bulk of the surge energy but may leave a residual voltage that can still stress sensitive electronics. A Type 3 device provides finer protection but lacks the energy handling capacity for direct lightning-induced surges. The EXU3DC-II+III combines both stages in one module, making it the correct choice for: DC inputs of EV fast chargers, where the power electronics are expensive, and downtime is costly; battery energy storage DC buses, where the battery management system and DC-DC converters need clean, clamped voltage; and inverter DC inputs, in utility-scale PV, where long DC cable runs increase exposure to induced surges.

OEM/ODM Supply – Two-Stage DC Surge Protection for Critical Infrastructure

Buyer’s Guide

How to Choose Between T2 and T2+T3 DC Surge Protection

Understanding when the EXU3DC-II+III’s two-stage design is the right specification.

1. T2 vs. T2+T3: The Protection Staging Concept

A Type 2 DC surge protector is designed for installation at the main DC distribution point — typically the combiner box output. It handles the bulk of the surge energy. A Type 3 device is installed closer to the protected equipment and provides a lower clamping voltage. The EXU3DC-II+III combines both stages in one DIN rail module, making it suitable for installations where the protected equipment is in the same enclosure as the SPD — such as integrated EV charger power modules or battery rack DC disconnects.

2. When T2+T3 Is the Better Choice

Select the T2+T3 DC SPD when the protected equipment is within the same panel as the SPD and cannot accept a high residual voltage. For example, a DC-DC converter in a battery storage system may have a transient withstand of 2.5kV — the EXU3DC-II+III’s staged protection ensures the voltage at the equipment terminals stays below this threshold. If the equipment is remote from the SPD (e.g., the inverter is 50m from the combiner box), a separate T3 SPD at the inverter end is still recommended.

3. 2P or 3P for Different DC Architectures

Select 2P for standard two-wire DC systems — positive and negative conductors. Select 3P when the DC system includes a center-tapped ground (bipolar PV arrays) or when the application requires surge protection between each conductor and ground plus conductor-to-conductor. EV charger DC outputs typically use 2P; some BESS architectures with floating DC buses may require 3P.

4. Integration with Backup Protection

The 125A gL/gG backup fuse must be installed in series with the SPD connection. In a combiner box, the existing string DC MCBs can serve this function. In a standalone SPD installation, a dedicated fuse holder must be provided. Always verify that the backup fuse rating does not exceed 125A and that it is installed upstream of the SPD.

Frequently Asked Questions

What is DC SPD?

A DC SPD is a protective device designed to shield DC circuits from voltage surges. It diverts excess energy from lightning strikes or switching events to ground, preventing damage to connected equipment. The EXU3DC-II+III is a T2+T3 DC SPD, meaning it combines two levels of protection in one unit: a high-energy Type 2 stage to handle the bulk of the surge, and a Type 3 stage for a lower, equipment-safe clamping voltage. This dual-stage design provides comprehensive protection for sensitive DC electronics in one compact, DIN-rail-mounted module.

What is the difference between AC and DC SPD?

The key difference is arc extinguishing. An AC SPD benefits from the alternating current’s zero-crossing to stop the flow of follow-on current after a surge. A DC SPD must break a constant DC arc without this help, so it uses a more robust thermal disconnect and a larger arc chute. Additionally, DC SPDs are rated for specific DC voltages like 800V, 1000V, or 1200V. The EXU3DC-II+III two-stage DC SPD is specifically designed and IEC 61643-1 certified for DC circuits. Using an AC SPD on a DC system, or vice versa, is unsafe and violates electrical codes because it cannot guarantee the arc will be extinguished.

How to connect DC SPD for solar?

To connect the EXU3DC-II+III DC SPD for solar, mount it on a 35mm DIN rail inside the PV combiner box or inverter DC cabinet. Wire it in parallel with the DC circuit: connect the positive and negative terminals of the SPD to the corresponding DC busbars. Connect the SPD’s ground terminal directly to the earth bar using a short, straight cable (ideally under 0.5m). If using the remote signaling feature, wire the switching contacts to the system’s alarm input. A backup fuse (max. 125A gL/gG) must protect the SPD connection. All connections should be made by a qualified electrician following local codes and the provided wiring diagram.

Can I use DC SPD for AC?

No. A DC SPD is engineered to break a DC arc and is rated for specific DC voltages. If you apply AC voltage to it, the internal components may not trigger correctly during a surge, or the SPD could fail to extinguish the arc, creating a safety hazard. Similarly, an AC SPD cannot safely handle DC surges. It is essential to use the correct type of device for the current in your system. The EXU3DC-II+III T2+T3 DC SPD is exclusively for DC applications, such as solar PV arrays, battery energy storage systems, and EV charging stations.