For a 300 KVA transformer providing power to a 180-amp load, what is the maximum rating for the secondary OCPD?

To determine the maximum rating for the secondary overcurrent protective device (OCPD) for a 300 KVA transformer supplying a 180-amp load, it is essential to consider the ratings and calculations involved in transformer protection.

According to the National Electrical Code (NEC), a transformer can typically have a secondary OCPD that is sized based on the full-load current of the transformer and the load characteristics. The full-load current of a transformer can be calculated using the formula:

[ I_{FL} = \dfrac{KVA \times 1000}{\sqrt{3} \times Voltage} ]

For a 300 KVA transformer at a standard output voltage (assuming a common secondary voltage like 480V or 240V), the maximum OCPD rating should normally be allowed up to 125% of the full-load current of the transformer or the load current, depending on the scenario.

In this case, if we consider a full-load current of around 300 KVA at a voltage that would commonly be used (for instance, 480V), this results in a significant current output. The maximum OCPD may typically be rated at 125% of the output load current.

Since the load