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AC current transformers provide ferrite core material

Posted: 18 Dec 2006     Print Version  Bookmark and Share

Keywords:power management  current transformer  LEM  split-core  transformer 

LEM S.A. has introduced the compACt TT series of split-core AC current transformers, which is said to offer high accuracy, linearity and very low phase shift, thanks to an innovative ferrite core material.

The core material used in the TT series transformers is a new type of ferrite with improved magnetic permeability, which enables the accurate measurement of AC signals within an extended frequency range that includes 50/60Hz. They feature an absolute accuracy better than one per cent at the nominal current and even better for lower primary currents, according to the company.

In addition, the ferrite material provides an excellent linearity of better than 0.1 per cent, even at very low levels, and the transformers offer a low phase shift of 1.5° ±1° between measured voltage and current. The hard and dense core allows very small air gaps and is insensitive to ageing and temperature changes, in contrast to laminated FeSi or FeNi materials, said the company.

The TT series transformers provide two ranges of primary current measurement at 50A and 100A. The TT 50-SD measures 36.5-by-43-by-31.5mm with an 8mm diameter sensing aperture for non-contact measurement. The TT 100-SD measures 44.5-by-51-by-36.5mm with a 16mm diameter sensing aperture.

Safe, easy installation
With a 3000:1 ratio, the TT 50-SD and TT 100-SD have low output currents (below 16.66mA or 33.33mA, respectively). 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 1A or 5A output products, said the company.

The TT series current transformers are suitable for distributed measurement systems and can be retro-fitted into existing installations and non-interruptible equipment. Other key applications include energy sub-metering (for measurement of active power and energy consumption), power quality monitoring, condition monitoring and process control. This series comes with a five-year warranty.

Pricing for the TT 50-SD and TT 100-SD is Rs.741.98 ($16.30) and Rs.842.12 ($18.50), respectively. Delivery is within seven weeks.

- Gina Roos

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