High-performance split-core current transformers for energy efficiency

Electrical Power & Protection

February 2007 Electrical Power & Protection

LEM has introduced the TT series of compact split-core AC current transformers. These new devices feature an innovative type of core material, enabling this technology to be the first to offer high performance coupled with an attractive price.

The core material used in the transformers is a new type of ferrite with improved magnetic permeability, allowing the accurate measurement of AC signals in an extended frequency range that includes 50/60 Hz. The new transformers feature an absolute accuracy better than 1% at the nominal current and even better for lower primary currents. The ferrite material provides an excellent linearity of better than 0,1% even at very low levels, and the transformers have a particularly low phase shift between measured voltage and current of 1,5° ±1°. The hard and dense core allows very small air gaps to be achieved and is virtually insensitive to ageing and temperature changes, in contrast to laminated FeSi or FeNi materials.

Two ranges of primary current measurement are available: 50 A and 100 A. The dimensions of the TT 50-SD are only 36,5 x 43 x 31,5 mm with an 8 mm diameter-sensing aperture for non-contact measurement. The TT 100-SD measures 44,5 x 51 x 36,5 mm with a 16 mm diameter-sensing aperture.

With a 3000:1 ratio, the TT 50-SD and TT 100-SD have low output currents (respectively below 16,66 mA or 33,33 mA). This, together with the internal output-protection circuit, guarantees safe and easy installation without the need to shut down operation since there is no risk of producing a high voltage surge when the transformers are opened, unlike 1 A or 5 A output products.

Being small, safe, self-powered and split-core, the TT current transformers are very easy to install and put into operation. They are ideal for distributed measurement systems and can be retro-fitted into existing installations and non-interruptible equipment. Principal applications will be in the field of energy sub-metering and cost allocation, dynamic consumption and peak analysis, energy waste or defective equipment detection and power quality control.

As with all other LEM industrial products, the TT transformers benefit from high-quality standards and are backed by a five-year warranty.

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Electrical Power & Protection

High-performance split-core current transformers for energy efficiency

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