CSLB C-46 Solar ContractorPlanning and EstimatingEasy
A solar contractor is preparing the final system design for a residential PV array. The design includes a string inverter and multiple strings of modules. To ensure proper operation and prevent potential damage to the inverter, what critical parameter must be carefully matched between the PV array and the string inverter?
- AThe physical dimensions of the modules and the inverter.
- BThe inverter's maximum DC input voltage and the array's maximum open-circuit voltage (Voc).
- CThe inverter's output AC voltage and the utility grid's frequency.
- DThe total weight of the PV array and the inverter's mounting capacity.
Show answer & explanationAnswer & explanation
Correct answer: B. The inverter's maximum DC input voltage and the array's maximum open-circuit voltage (Voc).
Matching the array's maximum open-circuit voltage (Voc) to the inverter's maximum DC input voltage limit is absolutely critical. If the array's Voc (especially at cold temperatures) exceeds the inverter's maximum input voltage, it can damage the inverter and pose a safety hazard. This is a fundamental design consideration for string inverters.
Why the other options are wrong
- A. Physical dimensions are for spatial planning, not electrical matching for operation.
- C. While AC voltage and grid frequency must match for grid-tied operation, the question is about matching between the array (DC) and the inverter (DC input side).
- D. Mounting capacity is a structural consideration, not an electrical parameter affecting inverter operation.
PV Array-Inverter Voltage Matching
Ensuring the PV array's maximum open-circuit voltage (Voc) does not exceed the inverter's maximum DC input voltage rating.
- Crucial for inverter safety and longevity.
- Voc increases at lower temperatures, requiring temperature correction.
- A fundamental step in string inverter system design.
Memory trick: Voltage high, inverter cry! Match the limits, keep it dry!