The Primary Winding Structure of The Current Transformer

March 23 , 2020
The primary winding structure of the current transformer has two forms of single-turn type and multi-turn type.

Single-turn type: The winding is only one turn at a time, and the structure is relatively simple. The primary current is more than 300 to 600A. It is divided into two types: bar type and bus bar type. Bar type: The primary winding is a copper rod, copper tube or copper bar that passes through the inner hole of the core. For example, the LA-10 type current transformer we produced now has a primary current of 300 to 1000A.

Bus bar type: There is no primary winding on the current transformer, which is the most convenient to make. When installed, the bus bar passes through the middle of the core window of the transformer, and is mainly used for current transformers with large currents above 600A. The LMZJ-0.5 current transformer is now produced using a bus bar type, whose primary current reaches a minimum of 100A (1 turn through the core) and when installed, the bus bar can also be wound around the current transformer core window by 2, 3 or 4 Turn, and get a transformer with a smaller current ratio.

Multi-turn type: The winding is more than one turn at a time, so the structure is more complicated than the single-turn type. Generally used for current transformers with a primary current below 300 to 600A, it is divided into winding type, back-chain type and figure 8 type.

Winding type:The primary winding is composed of ordinary winding. After the winding is wound, it is placed on the core,the LQG-0.5 current transformer produced now use this type.

Loop-back type: The primary winding passes through the holes of two insulation sleeves and is wound into a loop-back type. Currently only the LFC-10 type current transformer use it, and it is being replaced by a winding type.

“8”shape type: The primary winding passes through the inner hole of the Annular core, and the primary insulation is wrapped on the primary winding. In this way, the primary winding and the core constitute a figure-eight. Mainly used in high voltage outdoor power transformers above 35KV Device, such as current production LCW-35, 110 or 220 type current transformers.

In addition, according to the installation of power transformers, it can be divided into indoor, outdoor, and built-in types. Indoor type: Most current transformers and instrument current transformers below 10KV are indoor type and adopt dry insulation.

Outdoor: Current transformers above 35KV are all outdoor, using porcelain bottles and transformer oil insulation.

Built-in type: This type of circuit transformer has only an iron core and a secondary winding. It is mounted on the bushing of an oil circuit breaker or transformer, also called a bushing transformer. The conductive rod of an oil circuit breaker or transformer is the primary winding (1 turn) of the transformer, and the bushing insulation of the circuit breaker is the main insulation between the primary and secondary of the transformer. Therefore, the structure of this transformer is the simplest, and it is actually equivalent to an accessory of an oil circuit breaker or transformer.

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