User Manual

Planning for a Three-Phase IQ Microinverter System – North America

Interconnecting IQ Microinverters to Other Voltages

For interconnection to system voltages other than 120/240V single-phase, 120/208 single-phase, 208Y/120V

three-phase, and 240V high-leg delta three-phase, a transformer is required to interconnect to the grid.

While transformers interconnect Enphase Microinverter Systems to any utility power voltage, they also offer

other benefits.

• For many projects, it is cost effective to distribute the power at the higher utility voltages and then

step down the voltage to 208Y/120V or 240V high-leg delta at each sub-system. This practice results

in more transformers, but can be cost effective when wire runs are greater than 250 feet.

• Choose transformers with adjustable taps. Use the tap to make minor adjustments when the utility-

provided voltage is high or when optimizing conductor sizing versus expected voltage rise for the

value engineered PV system.

It is common to specify high-efficiency or ultra-high efficiency,

general purpose, dry-type transformers for an Enphase

Microinverter System. It is not necessary to specify power factor

correcting transformers or K-factor transformers.

Specify the transformer kVA size to meet the inverter output in kW

AC. Some additional deratings, such as adjustments for power

factor and temperature may apply. Refer to the transformer

manufacturer’s specifications for transformer sizing.

Most transformers for Enphase systems are specified as delta on

the primary/utility side and as 208/120 Wye or 240V high-leg delta

on the secondary/PV side. Even if the utility voltage is Wye, such

as a 480Y/277V service, it is still best to provide a delta

configuration with no neutral to the primary/utility side of the

transformer. This configuration works well, lowers wire costs, and

is recommended by the manufacturers of transformers for

improved performance and reduced harmonics.

Delta and Wye Wiring

The following table lists utility voltage values and transformer requirements.