Installing the DC Input Power Cable
Precautions
- Before connecting the DC input power cable, ensure that the DC voltage is within the safe range (lower than 60 V DC) and that the three DC switches on the inverter are set to OFF. Failure to do so may result in electric shocks.
- When the inverter operates in grid-tied mode, do not perform maintenance or operations on the DC circuit, such as connecting or disconnecting a PV string or a PV module in the PV string. Failure to do so may cause electric shocks or arcing, which may also cause fire.
Ensure that the following conditions are met. Otherwise, the inverter may be damaged, or even a fire could happen.
- The open-circuit voltage of each PV string must always be 1500 V DC or lower.
- The polarities of electric connections are correct on the DC input side. The positive and negative terminals of a PV module connect to corresponding positive and negative DC input terminals of the inverter.
- Ensure that the PV module output is well insulated to ground.
- The PV strings connecting to the same MPPT circuit should contain the same number of identical PV modules.
- The solar inverter does not support full parallel connection for PV strings (full parallel connection: PV strings connect to one another in parallel outside the solar inverter and then connect to the solar inverter separately).
- During the installation of PV strings and the inverter, the positive or negative terminals of PV strings may be short-circuited to ground if the power cable is not properly installed or routed. In this case, an AC or DC short circuit may occur and damage the inverter. The caused device damage is not covered under any warranty.
Terminal Description
The inverter provides 18 DC input terminals, which are controlled by its three DC switches. DC SWITCH 1 controls DC input terminals 1–6, DC SWITCH 2 controls DC input terminals 7–12, and DC SWITCH 3 controls DC input terminals 13–18.
Requirements for selecting DC input terminals:
- Evenly distribute the DC input power cables on the DC input terminals controlled by the three DC switches.
- Maximize the number of connected MPPT circuits.
Wiring Description of Y-branch Connectors
- Y-branch connectors can be purchased from Huawei or the manufacturers based on the following recommended models: If the rated current of the fuse of the Y-branch connector is 15 A, the recommended model is 904095944 (Luxshare) or A040959443039 (Comlink); if the rated current of the fuse of the Y-branch connector is 20 A, the recommended model is 904095945 (Luxshare) or A040959453039 (Comlink).
- When connecting cables to recommended Y-branch connectors, ensure that the connectors to be paired match each other and are from the same manufacturer. Otherwise, the contact resistance of the connectors may exceed the allowed value. In this case, the connectors may be heated and oxidized, which may cause faults.
- Ensure that the locking nuts of all connectors are tightened.
- Do not bind more than three fuse enclosures together. Otherwise, the fuses and their enclosures may be damaged due to overheating. It is recommended that a clearance of 10 mm or more be reserved between fuse enclosures. You are advised not to bind the fuse enclosures with other heat emitting conductors.
- Do not place the Y-branch connector harness on the ground. A safe distance must be reserved between the Y-branch connector harness and the ground to avoid impact caused by water on the ground to the harness.
- It is recommended that the Y-branch connectors be connected from the PV string side and tied to the PV trackers.
- The DC input terminals of the solar inverter are prone to damage under stress. When Y-branch connectors are connected to the solar inverter, bind and secure the connectors to minimize stress on the DC input terminals. For details, see Securing Y-Branch Connectors.
- The PV+ on the string side must be connected to the PV+ on the SUN2000 side, and the PV– on the string side must be connected to the PV– on the SUN2000 side.
- Preferentially and evenly connect the Y-branch connectors to the MPPTs controlled by DC SWITCH 1 or DC SWITCH 2.
Number of Y-branch Connector Sets
Recommended MPPT to Be Connected
Number of Y-branch Connector Sets
Recommended MPPT to Be Connected
1
MPPT1
2
MPPT1 and MPPT4
3
MPPT1, MPPT3 and MPPT4
4
MPPT1, MPPT3, MPPT4 and MPPT6
5
MPPT1, MPPT2, MPPT3, MPPT4, and MPPT5
6
MPPT1, MPPT2, MPPT3, MPPT4, MPPT5, and MPPT6
7
MPPT1, MPPT2, MPPT3, MPPT4, MPPT5, MPPT6, and MPPT7
8
MPPT1, MPPT2, MPPT3, MPPT4, MPPT5, MPPT6, MPPT7, and MPPT8
9
MPPT1, MPPT2, MPPT3, MPPT4, MPPT5, MPPT6, MPPT7, MPPT8, and MPPT9
N/A
N/A
Figure 5-15 Y-branch Connector SolutionScenario
Model of Y-branch Connector (Part A)
Connection Description
Connecting Y-branch connectors to the PV strings (recommended)
All models
Use the DC terminals delivered with the SUN2000s to connect part B to the SUN2000s.
Connecting Y-branch connectors to the SUN2000
Models recommended by Huawei
Part A can be directly connected to the SUN2000, and part B is not needed.
Other models
To ensure that the terminals of part A match the DC terminals of the SUN2000, part B is needed to connect part A to the SUN2000. Use the DC terminals delivered with the SUN2000 to connect part B to the SUN2000.
Cable Specifications
Cable Type |
Conductor Cross-sectional Area (Unit: mm2) |
Cable Outer Diameter (Unit: mm) |
|---|---|---|
PV cable that meets the 1500 V standard |
4–6 |
4.7–6.4 |
Cables with high rigidity, such as armored cables, are not recommended, because poor contact may be caused by the bending of cables.
Procedure
- Use the MC4 EVO2 PV connectors delivered with the inverter. If the PV connectors are lost or damaged, purchase the connectors of the same model. The device damage caused by incompatible PV connectors is beyond the warranty scope.
- For models of the crimping tool and removal wrench, use the recommended model or contact your Staubli dealer.
- Install the DC input power cable.
- The DC voltage measurement range of the multimeter must be at least 1500 V.
- If the voltage is a negative value, the DC input polarity is incorrect and needs correction.
- If the voltage is greater than 1500 V, too many PV modules configured to the same string. Remove some PV modules.
- Connect the PV string connector to the inverter connector, and then pull back the PV string connector along the axial direction to check whether the connectors are securely connected.
- The connector must be securely connected. Damages caused by improper connection are not covered under the warranty.
Figure 5-16 Cable connectionFigure 5-17 Connector connectionDuring DC input power cabling, leave at least 150 mm of slack. The axial tension on PV connectors must not exceed 80 N. Radial stress or torque must not be generated on PV connectors.
Figure 5-18 DC input power cabling requirement
