Types Of Transformer | Explain all transformer according their uses - Electrical4u

Types Of Transformer | difference CT and PT 

The Transformer are classified on the basis of various factors.

1. According to purpose of uses 

• Power Transformer 

• Distribution Transformer 

• Testing Transformer 

• Instrument Transformer 

2. According to insulation 

• Liquid - immersed Transformer

• Gas Filled Transformer 

• Dry Type Transformer 

3. According to number of phase

• Single phase transformer

• Three Phase transformer 

4. According to manufacturing & Designing 

• Core Type transformer

• shell type transformer 

5. According to their purpose 

• Step - Up Transformer 

• Step - Down Transformer 

Core Type Transformer

In the transformer , the magnetic circuit consists of two vertical legs or limbs with two horizontal sections called yokes . Half of each winding is placed on each legs to keep the leakage flux to a minimum . 

The High winding is placed around the low voltage winding is placed next to the core . Thus The Winding are arranged as concentric or cylindrical winding.

This Core Type Transformer are made either L Shaped , or U & I shaped 

Shell Type Transformer 

In The Transformer , Both primary and Secondary winding are wound on the central limbs and the two outer limbs complete the low reluctance flux paths. These Winding are subdivided into sections . These Sub Sections Are Low Voltage and High Voltage Sub Section Which are alternately placed in a sandwich formation . This Winding are known as sandwich or disc winding.  

The Shape Of shell type transformer is either I & E shapes or U & T Shapes 

Instrument Transformer

In high voltage circuit , It is Not practical to connect instrument and meters directly to the lines. Thus The range of AC instrument can be increased to a great extent by using instrument transformer , In this transformer standard rated instruments may be used 

The Instrument transformer is fundamentally same as Power transformer 

Generally Instrument Transformer is Two Types,

1. Potential Transformer  (PT)
2. Current Transformer  (CT)

Current Transformer is used to increase the Current range of AC Instrument whereas Potential Transformer are Used To increase the voltage range 

Potential Transformer  (PT)

It is step down transformer used to operate voltmeters and the potential coil of wattmeter and relays from high voltage line . This primary winding of PT is Connected across the high voltage supply and secondary winding to the voltage and potential coil of wattmeter. 

In this transformer earthing terminal should be on its body or frame and they should be connected to ELCB earthing . The secondary voltage is design is 100 to 120V is delivered to the instrument load. The normal secondary voltage rating is 110V. 

Current Transformer (CT)

Current Transformer is Avoid connecting AC ammeters and the current coils of others instruments and meter as well as relay coil directly to high voltage line . The Cross section area of core of a CT is made large , So As to reduce the working flux density.

A Shunt transformer and current transformer  are similar Functions.

The primary winding of a current transformer consist of a few turns of thick cross-section area . This Turn are connected with the high current line in series. 

Power Transformer

Transformer above  500kVA  rating which are used in generating station and substation for stepping up or Stepping down the voltage are called Power transformer. This type of transformer used in operation during the load periods and can be disconnected during light load periods However, in a substation at least one or two transformer should remain operational during light load periods. 

Maximum Efficiency of Power transformer at nearly 80% full load

Auto Transformer

A transformer in which a part of winding is common to both the primary and secondary circuits is known as an Auto Transformer . it is a transformer with a single winding only.