What Is a Clamp Current Transformer?

What Is a Clamp Current Transformer?

A clamp current transformer is a device that enables you to measure electric current without disconnecting it.clamp current transformer When a conductor passes through it, the magnetic field generated by the conductor induces a proportional current in its secondary coil. This secondary current can then be measured using a meter or data logger.

There are many different types of current clamps available on the market.clamp current transformer Some are made to work only with AC current, while others have a more flexible design that can also handle DC. A basic current clamp has a split ring of ferrite or soft iron, with a coil wound around one half and the conductor passed through the other. This type of clamp, sometimes called a Rogowski coil or passive transformer CT clamp, will only work with AC waveforms up to 1000’s of Hertz, so it should only be used for measuring AC current.

Another type of current clamp has a sensor built into its core. This has a gap or slit cut into the magnetic core, and when the magnetic field from the conductor passes through it, it generates a voltage in the sensor that can be measured with a voltmeter. This sensor-based model is sometimes referred to as an open loop current clamp because the voltage is read through an open circuit.

The most advanced current clamps use a solid-state Hall effect sensor. These can detect both AC and DC current, and often provide a true root mean squared (RMS) reading that is accurate to within 1% of the actual current. These types of clamps are often used by electricians, and are usually integrated into a multimeter or power analyzer.

There is a very wide range of CTs available, ranging from small portable digital models to large analog units that are integrated into smart meters. Each has its own advantages and disadvantages, so it’s important to select a CT for your specific application.

EV charging is a perfect example of how CTs can be deployed to monitor energy flows. By measuring live current, a charger or energy management system can ensure that demand does not exceed available capacity, and prevent fuse overloads. It can even enable solar-integrated systems to intelligently divert excess generation to EV charging, maximizing self-consumption and reducing electricity bills.

A new CT from DENT, the 150A Split Core EZ Clamp-On CT, is ideal for monitoring energy flows during EV charging. Designed for one-handed operation, it quickly clamps around insulated cables and wires to enable rapid measurement and verification in the field. This compact, battery powered CT can be used with the ELITEpro XC portable data logger for Measurement & Verification (M&V) or electrical load profiling, and it’s suitable for residential and commercial applications. It is cURus recognized, CE listed and RoHS compliant, with 600V CAT III rated protection.

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