Connecting DC Input Power Cables

Precautions

• Before connecting the DC input power cables, ensure that the DC voltage is within the safe range (lower than 60 V DC) and that the DC switch on the SUN2000 is OFF. Failing to do so may result in electric shocks.
• When the SUN2000 is running, it is not allowed to work on the DC input power cables, such as connecting or disconnecting a PV string or a PV module in a PV string. Failing to do so may cause electric shocks.
• If no PV string connects to a DC input terminal of the SUN2000, do not remove the watertight cap from the DC input terminals. Otherwise, the IP rating of the SUN2000 will be affected.

Ensure that the following conditions are met. Otherwise, the SUN2000 may be damaged, or even a fire could happen.

• The DC input voltage of the SUN2000 shall not exceed maximum input voltage under any circumstance.
• The polarities of electric connections are correct on the DC input side. The positive and negative terminals of a PV string connect to corresponding positive and negative DC input terminals of the SUN2000.
• If the DC input power cables are reversely connected, do not operate the DC switch as well as positive and negative connectors immediately. Wait until the night when solar irradiance declines and the PV string current drops to below 0.5 A. Then set the DC switch to the OFF position, remove the positive and negative connectors, and correct the polarities of the DC input power cables.

• Since the output of the PV string connected to the SUN2000 cannot be grounded, ensure that the PV module output is well insulated to ground.
• During the installation of PV strings and the SUN2000, 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 SUN2000. The caused device damage is not covered under any warranty or service agreement.

Figure 5-13 DC input terminals

Procedure

1. Assemble a DC connector.

   Use the Staubli MC4 positive and negative metal terminals and DC connectors delivered with the SUN2000. Using incompatible positive and negative metal terminals and DC connectors may result in serious consequences. The caused device damage is not covered under any warranty or service agreement.

   • Keep the DC input PV+ cable and PV– cable close to each other.
   • Cables with high rigidity, such as armored cables, are not recommended as DC input power cables, because poor contact may be caused by the bending of the cables.
   • Before assembling DC connectors, label the cable polarities correctly to ensure correct cable connections.
   • After crimping the positive and negative metal terminals, pull the DC input power cables back to ensure that they are connected securely.
   • Insert the crimped metal terminals of the positive and negative power cables into the appropriate positive and negative connectors. Then pull back the DC input power cables to ensure that they are connected securely.
   Figure 5-14 Assembling a DC connector
   
   • If the PV string is not configured with an optimizer, use a multimeter to measure the voltage at the DC position. The multimeter must have a DC voltage range of at least 600 V. If the voltage is a negative value, the DC input polarity is incorrect and needs correction. If the voltage is greater than 600 V, too many PV modules are configured to the same string. Remove some PV modules.
   • If the PV string is configured with an optimizer, check the cable polarity by referring to the Smart PV optimizer quick guide.

   Before performing Step 2, ensure that the DC switch is set to OFF.

2. Insert the positive and negative connectors into corresponding DC input terminals on the SUN2000.

   After the positive and negative connectors snap into place, pull the DC input power cables back to ensure that they are connected securely.

   Figure 5-15 Connecting DC input power cables
   

   If the DC input power cable is reversely connected and the DC switch is set to ON, do not immediately turn off the DC switch or reconnect the positive and negative connectors. Otherwise, the device may be damaged. The caused device damage is not covered under any warranty or service agreement. Wait until the night when solar irradiance declines and the PV string current drops to below 0.5 A. Then set the DC switch to the OFF position, remove the positive and negative connectors, and correct the polarities of the DC input power cables.

Follow-up Procedure

Before removing the positive and negative connectors, ensure that the DC switch is OFF.

To remove the positive and negative connectors from the SUN2000, insert a disassembly tool into the notch and press the tool with an appropriate force.

Figure 5-16 Removing a DC connector