Working Principle of a Current Transformer (CT)!!

A Current Transformer (CT) is an instrument transformer used to measure high currents in power systems by stepping them down to a lower, measurable value. It operates on the principle of electromagnetic induction.

Basic Operation:

1. Primary Winding: The primary winding is connected in series with the power circuit and carries the full load current.

2. Magnetic Induction: The current in the primary winding generates a magnetic field, inducing a proportional current in the secondary winding.

3. Secondary Winding: The secondary winding has more turns than the primary, and it produces a lower current proportional to the primary current.

4. Burden Resistance: The secondary current is fed to a measuring instrument or protective relay, ensuring the circuit remains closed.

Key Formula:

The transformation ratio of a CT is given by:

Ip / Is = Ns / Np

 Ip= Primary current

Is= Secondary current

Ns = Number of turns in the primary winding

Np= Number of turns in the secondary winding

Important Considerations:

The secondary circuit must always be closed (never open-circuited) to avoid high voltages that can damage the CT or pose safety risks.

CTs are designed for high accuracy in measurement and protection applications.

They are commonly used in power grids, industrial electrical systems, and energy metering.