Enter the CT ratio and the secondary current (amps) into the calculator to determine the Primary Current From CT Ratio.

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## Primary Current From CT Ratio Formula

The following formula is used to calculate the Primary Current From CT Ratio.

**Ip = CT * Is**

- Where Ip is the Primary Current From CT Ratio (amps)
- CT is the CT ratio
- Is is the secondary current (amps)

## How to Calculate Primary Current From CT Ratio?

The following two example problems outline how to calculate the Primary Current From CT Ratio.

**Example Problem #1:**

- First, determine the CT ratio. In this example, the CT ratio is measured to be 40.
- Next, determine the secondary current (amps). For this problem, the secondary current (amps) is calculated to be 5.
- Finally, calculate the Primary Current From CT Ratio using the formula above:

Ip = CT * Is

Inserting the values from above and solving the equation with the imputed values gives:

Ip = 40 * 5 = 200 (amps)

**Example Problem #2: **

Using the same process as example problem 1, we first define the variables outlined by the formula. In this case, the values are:

CT ratio = 60

secondary current (amps) = 3

Entering these values into the formula or calculator above gives us::

Ip = 60* 3 = 180 (amps)