Explore topic-wise InterviewSolutions in .

The RATIO of total cross section of iron to the total cross section of CORE is CALLED STACK factor.

The ratio of total cross section of iron to the total cross section of core is called stack factor.

This is because the CORE is laminated & on each lamination the INSULATIONS are are USED.

This is because the core is laminated & on each lamination the insulations are are used.

The CORE is constructed by sheet STEEL laminations assembled to provide a continuous MAGNETIC path with minimum of air gap included. The steel used is of high silicon content sometimes heat treated to produce a high permeability and a low hysteresis loss at the usual operating flux densities. The EDDY current loss is minimized by laminating the core, the laminations being used from each other by light coat of coreplate varnish or by oxide layer on the surface. The thickness of lamination varies from 0.35mm for a frequency of 50Hz and 0.5mm for a frequency of 25Hz.

The core is constructed by sheet steel laminations assembled to provide a continuous magnetic path with minimum of air gap included. The steel used is of high silicon content sometimes heat treated to produce a high permeability and a low hysteresis loss at the usual operating flux densities. The eddy current loss is minimized by laminating the core, the laminations being used from each other by light coat of coreplate varnish or by oxide layer on the surface. The thickness of lamination varies from 0.35mm for a frequency of 50Hz and 0.5mm for a frequency of 25Hz.

In ORDER to MINIMIZE EDDY CURRENT LOSS.

In order to minimize eddy current loss.

The sections of the CORE which connect the LIMBS are CALLED yoke. The yoke is used to PROVIDE a closed path for the flux.

The sections of the core which connect the limbs are called yoke. The yoke is used to provide a closed path for the flux.

• To reduce the SPACE effectively. 
• To OBTAIN reduced LENGTH of MEAN turn of the windings. 
• To reduce I² R loss. 

In this type of transformer the primary and secondary are same. When it is required to ISOLATE the primary and secondary circuits these type of TRANSFORMERS are USED. It protects the circuits CONNECTED in secondary side when major fault occurs in primary side.

In this type of transformer the primary and secondary are same. When it is required to isolate the primary and secondary circuits these type of transformers are used. It protects the circuits connected in secondary side when major fault occurs in primary side.

They STEP up VOLTAGE from HIGHER VALUE to LOWER value.

They step up voltage from higher value to lower value.

They STEP up VOLTAGE from LOWER VALUE to HIGHER value.

They step up voltage from lower value to higher value.

In this type of TRANSFORMER, oil is used as coolant. Entire assembly including core and windings is kept immersed in oil. The DEVELOPED heat is TRANSFERRED to the walls of tank through oil. FINALLY the heat is transferred to the surrounding air from tank wall by RADIATION.

In this type of transformer, oil is used as coolant. Entire assembly including core and windings is kept immersed in oil. The developed heat is transferred to the walls of tank through oil. Finally the heat is transferred to the surrounding air from tank wall by radiation.

In this type of transformer, air is used as coolant.The HEAT is taken to WALLS of tank and DISSIPATED to the SURROUNDING air.

In this type of transformer, air is used as coolant.The heat is taken to walls of tank and dissipated to the surrounding air.

They are protective devices USED to MEASURE very high value of VOLTAGE in POWER system.

They are protective devices used to measure very high value of voltage in power system.

They are protective devices USED to measure very high value of current in power SYSTEM. The Current Transformer ( C.T. ), is a TYPE of “instrument transformer” that is designed to produce an alternating current in its secondary winding which is PROPORTIONAL to the current being measured in its primary.

They are protective devices used to measure very high value of current in power system. The Current Transformer ( C.T. ), is a type of “instrument transformer” that is designed to produce an alternating current in its secondary winding which is proportional to the current being measured in its primary.

1. The distribution transformer will have low iron loss and higher VALUE of copper loss 
2. The CAPACITY of TRANSFORMERS will be up to 500 KVA 
3. The transformers will have plain walled TANKS or provided with cooling tubes or radiators. 
4. The leakage REACTANCE and regulation will be low. 

Distribution transformer is designed for maximum efficiency at 60% to 70% LOAD as it normally doesn’t operate at full load all the time. Its load depends on distribution DEMAND. Whereas power transformer is designed for maximum efficiency at 100% load as it always runs at 100% load being NEAR to generating STATION.

Distribution transformer is designed for maximum efficiency at 60% to 70% load as it normally doesn’t operate at full load all the time. Its load depends on distribution demand. Whereas power transformer is designed for maximum efficiency at 100% load as it always runs at 100% load being near to generating station.

The distribution transformer is used for the distribution of electrical energy at low voltage as less than 33KV in industrial PURPOSE and 440v-220v in domestic purpose. It works at low efficiency at 60-70%, SMALL size, EASY in installation, having low magnetic LOSSES & it is not ALWAYS fully loaded.

The distribution transformer is used for the distribution of electrical energy at low voltage as less than 33KV in industrial purpose and 440v-220v in domestic purpose. It works at low efficiency at 60-70%, small size, easy in installation, having low magnetic losses & it is not always fully loaded.

Power transformer is USED for the TRANSMISSION PURPOSE at heavy load, HIGH voltage greater than 33 KV & 100% efficiency. It is big in size as compared to distribution transformer, it used in generating station and Transmission substation. It is generally RATED above 200MVA.

Power transformer is used for the transmission purpose at heavy load, high voltage greater than 33 KV & 100% efficiency. It is big in size as compared to distribution transformer, it used in generating station and Transmission substation. It is generally rated above 200MVA.

Core type transformers are popular in High VOLTAGE APPLICATIONS like Distribution transformers, POWER transformers, and obviously auto transformers. Where as, Shell type transformers are popular in Low voltage applications like transformers used in electronic CIRCUITS and power electronic converters etc

Core type transformers are popular in High voltage applications like Distribution transformers, Power transformers, and obviously auto transformers. Where as, Shell type transformers are popular in Low voltage applications like transformers used in electronic circuits and power electronic converters etc

In SHELL type transformers the coils are well SUPPORTED on the all SIDES and so they can withstand higher mechanical stresses developed during SHORT circuit conditions. ALSO the leakage reactance will be less in shell type transformers.

In shell type transformers the coils are well supported on the all sides and so they can withstand higher mechanical stresses developed during short circuit conditions. Also the leakage reactance will be less in shell type transformers.

THREE WINDINGS in PRIMARY and three windings in secondary are used, They are three phase transformers.They are CONNECTED in either star-star, delta-delta, star delta or delta star.

Three windings in primary and three windings in secondary are used, They are three phase transformers.They are connected in either star-star, delta-delta, star delta or delta star.

THREE WINDINGS are used each work as PRIMARY and secondary. Also primary and secondary windings are conductively COUPLE. They are three phase AUTO transformer.

Three windings are used each work as primary and secondary. Also primary and secondary windings are conductively couple. They are three phase auto transformer.

TWO SEPARATE windings one as PRIMARY and other as secondary are used. Both windings are MAGNETICALLY coupled.

Two separate windings one as primary and other as secondary are used. Both windings are magnetically coupled.

In these TRANSFORMER only one winding is used as primary and SECONDARY. ALSO, primary and secondary are conductively coupled.

In these transformer only one winding is used as primary and secondary. Also, primary and secondary are conductively coupled.

The TRANSFORMER which works on SINGLE phase is called single phase transformer.
The transformer which works on THREE phase is called three phase transformer.

The transformer which works on single phase is called single phase transformer.
The transformer which works on three phase is called three phase transformer.

Based on supply

1. Single phase transformer 
2. Three phase transformer 

Based on winding

1. Auto transformer (single winding)
2. TWO winding transformer 
3. Three winding transformer 
4. Six winding transformer 

Based on CONSTRUCTION 

1. Core Type transformer 
2. Shell Type transformer 

Based on the service

1. Distribution transformer 
2. Power transformer 

Based on measurement

1. Current transformer
2. POTENTIAL transformer 

Based on COOLING

1. Dry type Transformer
2. Oil IMMERSED type transformer 

Based on function

1. Step up transformer 
2. Step down transformer
3. Isolation transformer

Based on supply

Based on winding

Based on construction 

Based on the service

Based on measurement

Based on cooling

Based on function

No

1. Transformer works on Faraday's law of Electromagnetic Induction for which current in COIL must change. If DC is applied current will not change and transformer will not WORK.
2. PRACTICALLY WINDING RESISTANCE is very small. For DC ,inductive reactance is zero and frequency is zero. Therefore impedance is low. Thus winding draws more current which may damage the winding.

No

Transformer consists of two coils.If one coil is connected with ac voltage source then it will PRODUCE alternating flux in the core. Most of the flux is linked with second coil hence mutually INDUCED emf will produce in the second coil as per faraday's law of ELECTROMAGNETIC INDUCTION.

Transformer consists of two coils.If one coil is connected with ac voltage source then it will produce alternating flux in the core. Most of the flux is linked with second coil hence mutually induced emf will produce in the second coil as per faraday's law of electromagnetic induction.

A TRANSFORMER is a static device which can transfer power from one CIRCUIT to ANOTHER at same FREQUENCY.

A transformer is a static device which can transfer power from one circuit to another at same frequency.