Current transformer cores for 20/40 A energy meters

30 January 2002 Passive Components

Electronic energy meters are worldwide more and more specified according to the international standard IEC 1036, or derived national standards. This means, they have to resist unipolar alternating currents including a DC portion without core saturation. Here, current transformers (CTs) containing traditional core materials are not suitable.

In preference to usual solutions, which mostly have technical drawbacks or are too expensive, Vacuumschmelze has designed CTs that use Vitrovac amorphous cores. For meters designed for 60, 100 or 120 A maximum current, the core types W639, W588 and W774 are an industry standard. For 20 and 40 A meters, VAC now offers two new cores: W592 (20 A) and W800 (40 A).

Also available are completely wound and cased CTs. According to the manufacturer, Vitrovac CTs fulfil all requirements easily: the amplitude-error is extremely low; phase angle error typically lies around 4° and is very constant, so that it can be compensated easily; the temperature dependence of all properties is also very small. Furthermore, Vitrovac cores require less space, compared to other materials and they offer a lower sensitivity against external fields.

Avnet Kopp, (011) 444 2333

[email protected]

www.avnet.co.za

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