Magnetics

what is a current sensing transformer?

Current Sensing Transformer: Magnetics Technology Explained

December 10, 2023 by Editing Team
3 min read

Introduction

A current sensing transformer (CST) is a type of transformer that is used to measure the current flowing in an electrical circuit. It works by inducing a small current in a secondary winding that is proportional to the current flowing in the primary winding. The current in the secondary winding can then be measured using a current transformer (CT) or a by connecting a known burden to the secondary and measuring the voltage across that burden.  These measurements on the secondary side are representative of the current flowing in the primary circuit.

One of the main advantages of using a current sensing transformer is its ability to measure current in an electrical circuit without making physical contact with the conductor. This makes it a non-intrusive method of measuring current, which is important in applications where making physical contact with the conductor is not feasible or safe.

Current sensing transformers can be designed to have high immunity to electromagnetic interference (EMI) and radio frequency interference (RFI), which makes them suitable for use in harsh industrial environments where these types of interference are prevalent.

Unlike standard current transformer which are typically designed for line frequencies, current sensing transformers can be designed to operate at much higher frequencies into the hundreds of kiliohertz.

In the field of power electronics, current sensing transformers are commonly used in a variety of applications, including:

Power measurement

Current sensing transformers are used to measure the current flowing in an electrical circuit, which is important for determining the power consumption of an electrical device or system.

Overcurrent protection

Current sensing transformers are used to detect overcurrent conditions in an electrical circuit and trigger protective measures to prevent damage to the circuit or equipment.

Motor control

Current sensing transformers are used to measure the current flowing in the stator windings of an electric motor, which is important for controlling the speed and torque of the motor.

Harmonic analysis

Current sensing transformers are used to measure the harmonic content of an AC power supply, which is important for identifying power quality issues and ensuring compliance with industry standards.

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