Current transformer construction types

Current transformer construction types

Moulded case feedthrough current transformer

The phase to be measured (conductor rail or line) is fed through the CT window and forms the primary circuit for the current transformer. Feedthrough transformers are predominantly used for mounting on bus bars. Through additional potting it is possible to achieve droplet-tightness, as well as greater shock and vibration resistance with mechanical loading (IEC 68).This is the most common form of current transformers, with the disadvantage that the primary conductor must be interrupted during installation. This form of transformer is therefore most commonly used in new system installations.

Split core current transformer

Split core current transformers are frequently used with retrofit applications. With these transformers the transformer core is open ready for installation, and is therefore fitted around the bus bars. This enables installation without interrupting the primary conductor.

Fig.: Split core current transformer
Fig.: Split core current transformer

Cable type split core current transformer

Cable type split core current transformers are exclusively suitable for installation in isolated primary circuit conductors (supply cables) in weatherproof and dry locations. Installation is possible without interrupting the primary conductor (i.e. with ongoing operation).

Fig.: Cable type split core current transformer
Fig.: Cable type split core current transformer

DIN rail current transformer with voltage tap and fuse

The DIN rail current transformer is a highly compact special variant with integrated voltage tap. The DIN rail current transformer comprises a terminal strip, current transformer and the voltage tap terminal with fuse. The fuse is fitted directly on the primary conductor and the unprotected part of the measurement line is therefore very short. This guarantees a high degree of intrinsic safety.

The DIN rail current transformer is simple to wire, results in low installation costs and a high degree of reliability due to few connections, and is also space- efficient and exhibits only very few connection faults.

Fig.: DIN rail current transformer
Fig.: DIN rail current transformer