What is CT ratio

Описание: What is CT ratio
CT ratio, in simpler terms, is the ratio between the current entering the current transformer (primary current) and the current leaving the current transformer (secondary current). Current transformers (CTs) are instrumental devices used to safely and accurately measure high-voltage currents.
CTs work by passing the primary conductor through a donut-shaped iron core. This core contains a secondary winding with many turns of wire. The current flowing through the primary conductor creates a magnetic field in the iron core. This magnetic field, in turn, induces a current in the secondary winding.
The CT ratio is expressed as a ratio of two numbers, such as 100:5 or 400:1. The first number represents the primary current, and the second number represents the secondary current. In the example of a 100:5 CT, for every 100 amps flowing through the primary conductor, 5 amps will flow through the secondary conductor.
There are two main reasons why CT ratios are important:
Safety: Because CTs reduce the current flowing in the secondary circuit, they allow us to use standard ammeters (instruments used to measure current) to measure high currents safely. High currents can be dangerous and can damage ammeters that are not rated for them.
Accuracy: By using a CT with the appropriate ratio, we can ensure that the ammeter reading is accurate. For example, if we are using a 100:5 CT with an ammeter that has a full-scale deflection of 10 amps, then the ammeter will read 1 amp for every 20 amps flowing in the primary circuit (10 amps / 5 amps/amp = 20 amps).