Let’s start with the necessary knowledge you need to understand what outdoor current transformers are and how they work.

What Is a Transformer, and How Does it Work?

A transformer is an electrical apparatus that is designed to convert alternating current from one voltage to another. It can be planned to either “step up” or “step down” works and voltages based on the magnetic induction principle. A transformer has no moving parts. This means that it’s an entirely static and solid-state device made to insure under normal operating conditions a long and hassle-free life.

A transformer is made of two or more coils of insulated wire wound which are placed on a laminated steel core. When voltage is introduced to one coil (the primary), it magnetizes the iron core. Then the voltage is induced into the other coil, which is called the output or secondary coil. The change of voltage, also known as voltage ratio, between the secondary and the primary is affected by the turns ratio of the two coils.

What Are Outdoor Current Transformers?

Current transformers, also known as “CT”, are devices used to transform current from high to low. In this way, power can be controlled and measured. This type of transformers can convert current to an accurate ratio so to allow an attached instrument to receive the current without running full power through the tool itself.

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An outdoor current transformer has a primary coil made with one or more turns of heavy wire. It is always connected in series in the circuit where the current is measured. The secondary coil is made of many turns of fine wire, which should always be connected across the ammeter terminals.

Outdoor current transformers are made of a core as well as a primary and a secondary winding. In particular, when an alternating current flows through the primary winding, that’s when a magnetic flux is created. Then it induces an alternating current in the secondary winding. After that, this alternating current is proportional to the current located in its primary.

Besides, outdoor current transformers are also known as “step-down transformers”. Once the current is reduced, you can safely monitor and measure it with an ammeter. Outdoor current transformers can perform circuit control. They can also play roles for current limiting and safety protection.

Here is where you can find outdoor current transformers:

  • Electrical substations
  • Generating stations
  • Commercial electric power distribution

What Are The Main Types of Outdoor Current Transformers?

  • Wound Current Transformer – This type of outdoor current transformer is connected physically in series to the conductor. The conductor carries the measured current and lets it flow in the circuit. The magnitude of the secondary current depends a lot on the turns ratio of the transformer.
  • Toroidal Current Transformer – These outdoor current transformers are shaped like a doughnut and don’t contain a primary winding. Besides, the line carrying the current, which is flowing in the network, is threaded through a hole or window in the toroidal outdoor current transformer. This type of outdoor current transformers is highly efficient and yet creates a minimal excess noise while at the same provide little excess leakage inductance.
  • Bar-type Current Transformer – This type of outdoor current transformer relies on the actual table or bus-bar of the main circuit. That’s its primary winding, which equals to a single turn. Bar-type outdoor current transformers are entirely insulated from the high operating voltage of the system. Besides, they are usually bolted to the device which is carrying the device.

How Do You Select Outdoor Current Transformers?

  1. Determine the primary voltage and frequency you need
  2. Select the secondary voltage that best suits your needs
  3. Establish the capacity required in volt-amperes. You can do so by multiplying the load current (amperes) by the load voltage (volts) for single-phase. You should always select a transformer which is larger than the actual load.


Now that you are more familiar with the concept of outdoor current transformers, it’s time to get yours. You can spend hours online searching for a suitable option, but we wouldn’t suggest you do that. That’s why we would recommend Guangdong Sihui Instrument Transformer Works as one of the most reliable outdoor current transformer manufacturers. Visit their official website to learn more.

Posted by Steven

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