Requirements for Use

The following guidelines are necessary when specifying or evaluating transformers for use with SMA inverters:

• Multiple Sunny Tripower or Sunny Highpower inverters connected in parallel can be interconnected to a single transformer.

• For Sunny Tripower 125 (STP 125-70), the number of allowed inverters at one transformer is limited to a maximum of 25.

• Standard distribution or service transformers are acceptable for interconnection to medium-voltage distribution systems.

• Sunny Tripower and Sunny Highpower inverters do not require electrostatic shielding between primary and secondary windings of transformers.

• The nominal voltage at the inverter electrical connection point (ECP) must match the nominal output voltage of the inverter.

• The rated power (kVA) of a transformer must be equal to or greater than the total nominal output power of all inverters connected to the transformer.

• The winding configuration of transformers to which the inverters are connected must be compatible with the inverter.

• The total impedance between the inverters and the point of common coupling must not exceed the allowable impedance levels.

• Transformers must be rated for the nominal frequency of the grid voltage at the grid connection point and the tolerances to be expected.

• The expected load (generation) profile and ambient temperature conditions of the PV system and the transformer must be considered when specifying transformer rated power (kVA), temperature rise and insulation class.

• SMA Solar Technology AG recommends specifying transformers with multiple connection taps to enable adaption to the local system voltage.

• Transformers should comply with all applicable standards based on the installation location.