enphase IQ8D-72-E-US Design Manual page 87

Figure 72: Phase balancing using QD Cable phase rotation when using center tap connector in QD-12-42-63 (15.1 ft Cable)
Conclusion:
• Phase rotation in QD Cable helps the IQ8D Microinverter system to achieve phase balance across all 3 phases.
The additional center tap connectors are configured in such a way that it does not affect the phase rotation of the QD
Cable and supports easy plug & play center feeding of branch circuit.
• If the number of Microinverters are in multiples of 3 and each branch circuit has 9 IQ8D Microinverters, then IQ8D
system shall have balanced configuration across all 3 phases.
Scenario 3: An IQ8D System with 42 Microinverters has 5 AC branch circuits of varied sizes and has used 15.1 ft QD
Cable SKU QD-12-42-63 with center feeding of AC branch circuit.
The following system diagram explains how the phase balancing is achieved using QD Cable rotation. Similar
methodology can be used for any system size when an AC branch circuit is center fed using center tapping connector.
NOTE: The QD-12-42-63 cable includes a center-tapping connector in an alternating pattern after sequences four and five connectors as
shown in Figure 73. One of the center tap connector shall remain unused during installation. Do not remove sealing cap from center tap
connector if not used during installation.
NOTE: Plan and install the system so that a maximum of six Microinverters are installed on one side of the a center-tapping connector
to limit Voltage rise <1% in QD Cable. Refer to the section "Design Considerations for Voltage Rise in Commercial PV Design Guide
IQ8D Microinverter System" for details on voltage rise calculations and installation guidelines for center tapping of branch circuit with
QD-12-42-63 cable installations.
NOTE: Scenario 3 assumes no connectors are skipped during the installation. If installations require skipping few connectors, refer
scenario 5 to assess impact on the phase balancing.
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