Current Transformer

CURRENT TRANSFORMER

In laboratories the experiments which are done by the students are having rated currents which are easily measured by ammeters, but it is not possible to measure large currents with ammeters (such as current coming from substation). To avoid such circumstances current transformer is used.

What is current transformer?

Current transformer is a device or an instrumental transformer, at certain operating conditions the secondary current is proportional to primary current.

Constructional details:

The above figure exclaims current transformer, there are two windings named primary and secondary.

* The secondary transformer has small cross sectional area and more number of turns, the ammeter ranging up to 15Amp is connected in series with it.

* Depending upon the primary winding construction, current transformer are classified into two types

1. Wound type

2. Bar type

The wound type transformer having more than one complete turn and fixed in construction where as bar type transformer is adjustable to size and shape.

The main parts of the current transformer are

i) Core

ii) Windings

iii) Insulation

i) Core:

Wound type	Bar type
1. Core is made up of Nickel iron or oriented electric steel	1. Core is made up of Nickel iron or oriented electric steel
2. The shape of the core is rectangular or stadium or ring shaped	2. The shape of the core is ring shaped
3. Rectangular shaped cores are used for current transformer when works on high voltage lines due to less insulation and less current applications.	3. By using ring shaped core, low reluctance, low magnetizing current, low reluctance path and negligible flux is taken into consideration.