What is Electrical CT, CT types, Current Transformer in full detail

Current Transformers :
Q. State the specifications of CT as a protective transformer.

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• The instrument transformers, which used in conjunction with ammeter, over current relay etc. are known as current transformers.
• Current transformers step down current from high value to a low value.
• Their current ratio is substantially constant for given range of primary current and phase angle error is within specified limits.
• The VA rating of current transformers is small as compared with that of a power transformer.

Type of construction of CT's :
Ring type CT or Window type CT :
This is the simplest type of CT. The core has three types of popular shapes :
(1) Rectangular shape
(2) Oval shape
(3) Ring shape

Bar primary current transformers :

• The core is of a Nickel-Iron Alloy, or grain orients, sheet steel.
• The core is continuously wound type. Before applying secondary winding, the core is insulated by means or end collars and circumferential wraps.

• Recently the continuously wound cores are available in encapsulated form. Synthetic resins are used as encapsulating material.
• The material is applied by fluidised beds or electrostatic spraying.
• The secondary winding conductor is then, Is then wound as the insulated core in the form of toroidal winding by hand winding or toroidal winding machine.

• The secondary winding is then completely w sly wrapped by external tape with or without exterior ring ends and circumferential insulating wraps.

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