September 24, 2009

Transformers: Current sense transformers for currents up to 40 A

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EPCOS has extended its product range by four current sense transformers: the new series was developed on the basis of an EE12.6 ferrite core and is suitable for measuring alternating currents of up to 40 A. It complements the portfolio of transformers with E4.2 and EE5 ferrite cores.

Thanks to their SMT design, the new current sense transformers are particularly suited for compact DC/DC converters. The primary winding of the complete solution consists of an external yoke. The DC resistance of the primary winding is 0.28 mΩ for all types, the rated current is 40 A. The new transformers are available with inductances of between 1.4 and 22.4 µH and secondary-side DC resistances of between 400 and 2500 mΩ. Their turns ratios are between 1:50 and 1:200 and they have a test voltage of 1500 V AC. All new current sense transformers are compatible with existing designs based on EE12.6 cores.

Current measurement via current sense transformers is limited to AC applications. The current to be measured is applied to the primary winding of the transformer and a voltage signal proportional to the current is detected on the secondary side. The advantages of this technique are very low losses and high reliability, ruggedness and simple implementation. Current sense transformers are used wherever a control function, a protective circuit or load detection are required.

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