How To Size Current Transformers?

How to Size A Current Transformer

Sizing a current transformer will tell you if it is large enough to fit around the conductor being monitored.

In order to size a current transformer, you need to determine the VA rating of the transformer. The VA rating determines the maximum secondary impedance (burden) that can be driven at the stated accuracy.

Watch this educational video for an illustrated calculation example.

A Brief Review Of Current Transformers

A current transformer, which measures electrical currents, creates a reduced current proportional to the circuit’s current (1/N x I) and isolates the circuit from the measuring equipment. You can place it at any location on a board without affecting connectivity.

How to Select A Current Transformer

When it comes to CTs, there are a few different things you’ll want to consider before making your final choice.

The first is the type of current. If you’re looking for a transformer that will allow you to monitor current in a place where there’s only one phase or wire, then a single-phase or three-phase CT may be the best choice for you.

If you want to monitor a four-wire system or something with more than three phases (like a three-phase motor), then you’ll most likely need to use a four-wire CT.

The second thing you’ll want to think about when choosing a CT is how much voltage it can handle. Some CTs are designed for low voltage applications like monitoring power lines, while others are able to handle high voltages like those found on transmission lines.

If you’re not sure what voltage range your application falls into, talk with your sales rep before making any decisions!

Our team can help you make the best selection and provide recommended current transforms from our collection if needed.