Design of current transformers

Knowledge database

Feedthrough current transformer

The conductor to be measured (busbar or cable) is fed through the window opening and forms the primary circuit of the feedthrough current transformer. Feedthrough current transformers are mainly used for mounting on busbars. Drop resistance is achieved through additional encapsulation as well as higher shock and vibration resistance under mechanical stress (IEC 68). This is the most common type of current transformer, with the disadvantage that the primary conductor must be interrupted during installation. In other words, this transformer design is mainly used when setting up new systems.

Bauform-Stromwandler-TM800 — Fig.: Split transformer

Split transformers (separable current transformers)

Split-core transformers are often used in retrofit applications. With these transformers, the transformer cores can be opened for installation and thus mounted around the busbars. This enables installation without interrupting the primary conductor.

Bauform-Stromwandler-KUW1A — Fig.: Split core transformers

Split core transformers

Split core transformers are only suitable for installation on insulated primary circuit conductors (supply cables) in a dry location protected from the weather. Installation is possible without interrupting the primary conductor (i.e. during operation).

Bauform-Stromwandler-CT35-1A 64-1A — Fig.: DIN mounting rail transformers

DIN mounting rail transformer with integrated back-up fuse

The DIN rail current transformer is a very compact custom design with an integrated voltage tap-off. The DIN rail current transformer consists of a terminal block, current transformer, and voltage tap-off terminal with fuse. The fuse is mounted directly on the primary conductor, and therefore the unprotected part of the measuring cable is very short. This ensures a high level of intrinsic safety.

The DIN rail current transformer allows simple wiring, low installation costs, and greater reliability thanks to fewer connections, space savings, and fewer connection errors.