Factors Affecting the Calculation:
* Voltage: A 250 kVA transformer can have different voltage ratings on the secondary side (the side that feeds your panels). The voltage determines the current capacity for a given kVA rating.
* Load Type: The type of load connected to the panels affects the calculations. Continuous loads require a different derating factor than non-continuous loads.
* Code Requirements: Local electrical codes have specific rules regarding panel sizing, wire sizing, and overcurrent protection.
* Power Factor: The power factor of the load impacts the actual power consumption. A lower power factor requires a larger transformer capacity.
* Transformer Efficiency: Transformers aren't 100% efficient; some energy is lost as heat. This needs to be accounted for.
How to Calculate:
1. Determine the transformer's secondary voltage: This information is usually found on the transformer nameplate.
2. Calculate the available current:
* kVA = (Voltage x Current) / 1000
* Rearrange to solve for current: Current = (kVA x 1000) / Voltage
3. Factor in code requirements: Check local electrical codes for allowable load factors, wire sizing, and overcurrent protection for the specific type of load.
4. Determine the maximum number of panels: Divide the available current by the current rating of each panel (200 amps).
Example:
Let's assume the transformer has a secondary voltage of 480 volts.
* Current = (250 kVA x 1000) / 480 volts = 520.8 amps
* Assuming a load factor of 80% (due to code requirements), the available current is 520.8 amps * 0.8 = 416.6 amps.
* Maximum number of panels: 416.6 amps / 200 amps per panel = 2.08 panels
Important Note: This is a very simplified example. Always consult with a qualified electrician to determine the correct number of panels and ensure compliance with local electrical codes. They will take into account all the factors mentioned above to provide a safe and accurate installation.
