SMA SUNNY CENTRAL 900CP XT - Checking the Output Voltage of the Inverter; Checking the DC Voltage

4 Commissioning
SMA Solar Technology AG
User Manual 31SCCPXT-E7-BA-en-58
5. Check the output voltage of the inverter (see Section4.4.2, page31).
6. Check the DC voltage (see Section4.4.3, page31).
7. Mount the protective covers (see Section9.1.2, page77).
8. Mount the panels (see Section9.1.1, page76).
9. Switch on the supply voltage and the AC disconnection unit (see Section4.4.4, page32).
4.4.2 Checking the Output Voltage of the Inverter
1. Use a rotating field instrument to measure whether a right-hand rotating magnetic field is connected at the AC
connection brackets.
If a left-hand rotating magnetic field is detected, two line conductors must have been wrongly connected.
• Swap the connections L1 and L3.
2. Check whether the AC voltage is approximately the same as the nominal voltage of the inverter. Measure the AC
voltage between the terminals at the AC connection brackets and record in the commissioning report.
If the AC voltage differs significantly from the nominal voltage of the inverter, the transformation ratio of the MV
transformer must be adjusted by a duly authorized person.
4.4.3 Checking the DC Voltage
DANGER
Danger to life due to electric arcs if measuring device is not connected correctly
If the measurement points are incorrectly contacted, this can cause an electric arc. Electric arcs can result in death
or serious injury.
• Select the appropriate measurement range on the measuring device.
• Wear suitable personal protective equipment for all work on the device.
• Select correct measurement points.
NOTICE
Damage to the inverter due to excessive DC voltages
The DC voltage of the PV array must not exceed the maximum voltage of the inverter.
• Make sure the maximum voltage is no more than 1,000V.
Procedure:
1. Measure the DC voltage for each input and record it in the commissioning report. Use the DC+ and DC‒
connection brackets as measuring points.
2. Check that the DC voltages do not exceed the maximum DC voltage of the inverter.
If the DC voltages differ from one another or exceed the maximum DC voltage, make sure that the cabling of the
PV modules has been configured in accordance with the circuit diagram.
3. Make sure that the polarity of each input is correct.
4. Measure the DC voltage for each non-grounded pole to ground and record in the commissioning report. Use the
connection brackets of the ungrounded terminal and the grounding busbar as check points.
☑ There is a measurable voltage drop.
✖ There is no measurable voltage drop?
A ground fault is present.
• Eliminate the ground fault.