CT Ratio Calculator

Current Transformer (CT) Ratio Calculator

A current transformer’s CT ratio is a measurement that determines the ratio between the primary & secondary currents (or) capacitances of the transformer.

A magnetic core is utilized in the process of measuring alternating currents (AC) via a device known as a current transformer.

As a result of the flow of current through the primary winding, a magnetic flux is generated, which in turn causes a voltage to be induced in the secondary winding.

For the purpose of shielding the components of the circuit from the effects of large transients brought on by switching or fault circumstances, a CT is often positioned between the source & the load.

These devices are utilized for the purpose of measuring alternating current (AC) currents of all waveforms, including pulsed currents; however, power supply circuits that use switch mode can also contain them.

They are utilized in cases in which the CT is not physically situated in close proximity to the power source, & there is concerned regarding the accuracy of power current measurements.

The core of a current transformer is made up of numerous thin layers of steel lamination that are layered together to form a single unit. In order to establish the range of current that will be measured & whether the device will have a low resistance or a high resistance, the number of these laminations is the determining factor.

When it comes to CTs, the best ones have as few laminations as possible and short wire lengths between them.

This helps to reduce

  • Leakage inductance &
  • Hysteresis effects,

both of which are important sources of error in CTs.

When designing CT, one of the most important steps is to choose the suitable CT ratio. There are two primary parameters that have an effect on it: the maximum load current and the maximum short circuit current simultaneously. In an ideal condiion, the CT ratio should be higher than the rated current, which is normally at around 120%.

CT Ratio = Primary Current / Secondary Current

CT Ratio = IP/IS


CT Ratio – Current Transformer Ratio

To calculate the CT ratio, simply divide the primary transformer current by the secondary transformer current.

In order to calculate the CT ratio, go to the calculator and enter both the primary and secondary currents of the transformer.

By calculating this ratio, you may determine the level to which the current reduced as it flows through the transformer.

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