Enter the total number of amps and select the transformer size to determine the maximum overcurrent protection.

- All Electrical Calculators
- Transformer Calculator
- Transformer Amperage Calculator
- Transformer Impedance Calculator
- Circuit Breaker Size Calculator
- Fusing Current Calculator
- CT Ratio to Current Calculator

## Fusing Transformer Formula

The following formula is used to calculate the maximum over protection current a fusing transformer should support.

FS = TA * OF

- Where FS is the fusing overcurrent protection amps
- TA is the transformer primary current (amps)
- OF is the overcurrent protection factor
- = 125 % for 9 amps or more
- = 167% for 2-8.99 amps
- = 500% for less than 2 amps

## Definition

**What is fusing transformer? **

Fusing transformer is the process of protecting a transformer with fusing so that it can handle larger amounts of current.

## Example Problem

**how to calculate overprotect**i**on for fusing transformer? **

First, determine the total amperage the transformer will see. In this example, the total amperage is 7 amps.

Next, reference the list above for how much of an overprotection factor the transformer should have. In this case, it is 167%

Finally, calculate the fusing transformer amperage required:

FS = TA * OF

FS = 7 * 1.67

FS = 11.69 amps