current transformers vs voltage transformers: What’s the Difference?

Current transformers and voltage transformers (also called voltage transformers) are measuring devices. CT reduces the current signal for measurement purposes, while PT reduces the high voltage value to a low voltage value. These transformers are designed to measure the accuracy and safety of the power system.

In addition, CT and PT transformers reduce the current and voltage from high to low values. The structure of current transformer and voltage transformer is similar, because their primary winding and secondary winding have a magnetic circuit.

In any case, they have obvious differences. This article breaks down current transformers and potential transformers, and emphasizes the difference between the two.

1. What are current transformers and voltage transformers

Current Transformer

A current transformer is a device that measures alternating current. They are widely used to measure high-intensity currents.

Current transformers basically reduce high currents to a safer level, allowing you to handle them safely.It reduces the current to be measured so that you can measure it with an average range ammeter.

2. The functions of current transformers include:

  • Convert a large primary current into a small 1A/5A current
  • Provide current for the coil of the measuring device and protection relay
  • Separate primary voltage and secondary voltage.
  • The characteristics of current transformers include:
  • The current coil resistance of the instrument connected to the CT secondary winding is small. CT transformer is running close to short circuit under normal conditions
  • The primary winding is installed in series in the current.

Potential Transformers

On the other hand, voltage transformers, also called voltage transformers, measure one aspect of the power supply. Current transformers measure current, and potential transformers measure voltage.

Most American households use different voltages for different purposes.

3. The functions of voltage transformers include:

  • It measures and reduces the high voltage value to a smaller value
  • The voltage transformer converts the high voltage into a standard secondary voltage of 100V or lower in proportion to facilitate the protection and use of measuring instruments/equipment
  • Use PT to isolate high voltage from electrician.

 

Voltage transformers vs. current transformers

Function

One of the main differences between CT and PT transformers is their function.

On the one hand, the current transformer reduces the high current to a level that is safer, easier to control, and easy to measure. It converts a large primary current into a small 1A/5A current, which can be measured on an ammeter.

On the other hand, the potential (voltage transformer) measures and reduces the high voltage value to the low voltage value. It converts the high voltage to a standard secondary voltage of 100V or lower.

Type

Current transformers are divided into two types: winding type and closed type. Voltage transformers are also divided into two types (types), including electromagnetic voltage and capacitive voltage.

Connect

In a current transformer, the primary winding is connected in series to the transmission line of the current to be measured, and the full-line current flows through the winding. On the other hand, voltage transformers are connected in parallel with the circuit, which means that the full-line voltage appears on the windings.

Transformation ratio

The rate of change of the current transformer is higher, and the rate of change of the voltage transformer is lower.

Primary winding and secondary winding

In a current transformer, the primary winding has fewer turns and carries the current to be measured. In a voltage transformer, the primary winding has many turns and carries the voltage to be measured.

In a current transformer, the secondary winding has a large number of turns on the secondary side and is connected to the current winding of the instrument. In a voltage transformer, the secondary winding has a small number of turns on the secondary side and is connected to an electric meter or instrument.

Core

The current transformer adopts silicon steel laminated design, and the potential transformer adopts high-quality steel with low magnetic flux density.

Primary current

In a current transformer, the primary current does not depend on the conditions of the secondary side circuit. On the other hand, in a voltage transformer, the primary current depends on the secondary circuit conditions.

Use

When measuring high currents, such as 200 amps, you can use a 5 amp ammeter. On the other hand, for voltage transformers, a 120V voltmeter can be used to measure high voltages such as 11KV.

Secondary side

In a current transformer, the secondary side cannot be opened during use. On the other hand, in a voltage transformer, you can disconnect the secondary side without any damage.

Input value

In a current transformer, the input value is a constant current, while in a potential current, the input value is a constant voltage.

Secondary winding range

In the current transformer, the range is 1A or 5A, and in the potential transformer, the range is 110V.

Burden

The current transformer does not depend on the secondary load, while the voltage transformer depends on the secondary load.

application

Current transformers have different applications, including measuring current and power, monitoring grid operation, and operating protective overlays.

On the other hand, potential transformer applications include power supply, measurement, and operation protection coverage.

Generally speaking, the secondary side of the current transformer is allowed to be short-circuited, but not allowed to be open. On the other hand, the secondary side of the voltage transformer allows an open circuit, but not a short circuit.

Conclusion

Finally, the current transformer and voltage transformer are tested to ensure the normal operation of the transformer. It also ensures that the voltage and current stay within the prescribed framework. Transformers ensure that your electronic equipment or household appliances are protected from sudden electrical problems.

For the difference between current transformer and voltage transformer, please contact an electrical professional for more help and further information.

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