Connecting Cables to Staubli MC4 Connectors

Specification Requirements

Cables with high rigidity, such as armored cables, are not recommended, because poor contact may be caused by the bending of cables.

Use the Staubli MC4 connectors delivered with the solar 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.

Procedure

1. Prepare the DC input power cables.
2. Crimp positive and negative metal contacts.
3. Insert the contacts into the corresponding positive and negative connectors.
4. Tighten the lock nuts on the positive and negative connectors.
5. Use a multimeter to measure the voltage between the positive and negative terminals of the PV string (measurement range no less than 1100 V).
   • If the voltage is a negative value, the DC input polarity is incorrect and needs correction.
   • If the voltage is greater than 1100 V, too many PV modules configured to the same string. Remove some PV modules.
6. Use an insulation resistance tester to test the insulation resistance between the PV– cables and the ground: Add 1500 V DC voltage between the PV– cables and the ground and check the insulation resistance.
   • If the insulation resistance is greater than or equal to 1 MΩ, it is normal.
   • If the insulation resistance is less than 1 MΩ, troubleshoot the cable insulation.
     Figure 5-28 Testing the insulation resistance
     

     You can use a self-made tool to connect all PV– cables together through an adapter to test the insulation resistance between all PV– cables of a device and the ground at a time.

     Figure 5-29 Testing the insulation resistance between all PV– cables and the ground
     
7. Insert the positive and negative connectors into the corresponding DC positive and negative input terminals of the solar inverter.
   Figure 5-30 Connecting DC input power cables
   
   Figure 5-31 Connector connection
   
   • If the DC input power cable is reversely connected and DC switches are set to ON, do not immediately turn off the DC switches or reconnect the positive and negative connectors. Otherwise, the device may be damaged. The caused device damage is not covered under any warranty. Wait until the solar irradiance declines at night and the PV string current reduces to below 0.5 A. Then, turn off the three DC switches, remove the positive and negative connectors, and rectify the connection of the DC input power cable.
   • 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 5-32 DC input power cabling requirement
   

   During DC input power cabling, leave at least 50 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.