What is the fuse size required for the 50 kVA transformer bank?

To determine the appropriate fuse size for a 50 kVA transformer bank, it's essential to first calculate the full-load current based on the transformer's rating. The full-load current can be calculated using the formula:

Full Load Current (Amps) = kVA × 1000 / (Voltage × √3) for three-phase transformers, or

Full Load Current (Amps) = kVA × 1000 / Voltage for single-phase transformers.

Considering a three-phase transformer as is common in many applications, and using a standard voltage level of 480 volts for calculation, the full-load current would be calculated as follows:

Full Load Current = 50 kVA × 1000 / (480V × √3) ≈ 60.2 amps.

The fuse sizing for transformers typically also considers a fuse rating that is sufficiently above the full-load current but within safe limits to protect the transformer from damage due to overload or faults. A common practice is to size fuses at 125% of the transformer’s full-load current for primary fusing.

Taking the calculated full-load current of approximately 60 amps, 125% would yield about 75 amps as a recommended fuse size to provide adequate protection to the transformer while allowing for some