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Transformer voltages are fixed by system requirements. The ratio of these voltages to the number of TURNS in the winding determines the AMOUNT of magnetization. This ratio of voltage to turns is determined MAINLY for economical SOUNDNESS. THEREFORE the amount of flux at the normal voltage is fixed. This also fixes the level of noise and vibration.

Transformer voltages are fixed by system requirements. The ratio of these voltages to the number of turns in the winding determines the amount of magnetization. This ratio of voltage to turns is determined mainly for economical soundness. Therefore the amount of flux at the normal voltage is fixed. This also fixes the level of noise and vibration.

Transformer noise is caused by a phenomenon which causes a piece of magnetic sheet steel to extend itself when MAGNETIZED. When the magnetization is TAKEN away, it goes back to its original condition. This phenomenon is scientifically referred to as magnetostriction. A transformer is magnetically excited by an alternating voltage and current so that it becomes extended and contracted twice during a full cycle of magnetization.

The magnetization of any given point on the sheet varies, so the extension and contraction is not uniform. A transformer core is made from many SHEETS of special steel to REDUCE losses and moderate the ensuing heating effect. The extensions and contractions are taking place erratically all over a sheet. These extensions are proportionally and therefore not normally visible to the naked eye. However, they are sufficient to cause a vibration, and consequently noise. Applying voltage to a transformer produces a magnetic flux, or magnetic lines of force in the core. The degree of flux DETERMINES the amount of magnetostriction and hence, the noise level.

Transformer noise is caused by a phenomenon which causes a piece of magnetic sheet steel to extend itself when magnetized. When the magnetization is taken away, it goes back to its original condition. This phenomenon is scientifically referred to as magnetostriction. A transformer is magnetically excited by an alternating voltage and current so that it becomes extended and contracted twice during a full cycle of magnetization.

The magnetization of any given point on the sheet varies, so the extension and contraction is not uniform. A transformer core is made from many sheets of special steel to reduce losses and moderate the ensuing heating effect. The extensions and contractions are taking place erratically all over a sheet. These extensions are proportionally and therefore not normally visible to the naked eye. However, they are sufficient to cause a vibration, and consequently noise. Applying voltage to a transformer produces a magnetic flux, or magnetic lines of force in the core. The degree of flux determines the amount of magnetostriction and hence, the noise level.

• It can raise or lower the voltage or current in an AC circuit.
• It can act as an impedance transferring device by INCREASING or decreasing the VALUE of a capacitor, inductor or resistance in an AC circuit.
• It can isolate two CIRCUITS electrically.
• It can be USED to prevent DC from PASSING from one circuit to another

The transformers RATED below 1 KVA can be used on 50 Hz service. Transformers 1 KVA and larger, rated at 60 Hz, should not be used on 50 Hz service, due to the higher losses and resultant HEAT rise. Special designs are required for this service. HOWEVER, any 50 Hz TRANSFORMER will operate on a 60 Hz service.

The transformers rated below 1 KVA can be used on 50 Hz service. Transformers 1 KVA and larger, rated at 60 Hz, should not be used on 50 Hz service, due to the higher losses and resultant heat rise. Special designs are required for this service. However, any 50 Hz transformer will operate on a 60 Hz service.

Humming is a sound, which is PRODUCED DUE to the vibration of the cores in the transformer. The vibrations are produced due to the CHANGE in polarity of an alternating current or VOLTAGE and by the loose of lamination of the core. Both can be minimised by tightening the core of the transformer.

Humming is a sound, which is produced due to the vibration of the cores in the transformer. The vibrations are produced due to the change in polarity of an alternating current or voltage and by the loose of lamination of the core. Both can be minimised by tightening the core of the transformer.

The COOLING tubes will IMPROVE the circulation of OIL. The circulation of oil is due to effective PRESSURE heads produced by COLUMNS of oil in tubes. The improvement in cooling is accounted by taking the specific heat dissipation due to convection as 35% more than that without tubes.

The cooling tubes will improve the circulation of oil. The circulation of oil is due to effective pressure heads produced by columns of oil in tubes. The improvement in cooling is accounted by taking the specific heat dissipation due to convection as 35% more than that without tubes.

In transformers the LEAKAGE REACTANCE is reduced by INTERLEAVING the high voltage and low voltage WINDING. 

In transformers the leakage reactance is reduced by interleaving the high voltage and low voltage winding. 

COOLING TUBES are provided to INCREASE the heat DISSIPATING AREA of the tank. 

Cooling tubes are provided to increase the heat dissipating area of the tank. 

The HEAT dissipation of a TRANSFORMER occurs by CONVECTION, CONDUCTION and radiation.

The heat dissipation of a transformer occurs by convection, conduction and radiation.

The choice of cooling method DEPENDS on KVA RATING of TRANSFORMER, size, application and the site CONDITIONS where it will be installed. 

The choice of cooling method depends on KVA rating of transformer, size, application and the site conditions where it will be installed. 

Air natural, Air BLAST, Oil Natural, Oil natural air FORCED, Oil natural WATER forced, Oil forced, Oil forced air natural, Oil forced air natural, Oil forced water forced. 

Air natural, Air blast, Oil Natural, Oil natural air forced, Oil natural water forced, Oil forced, Oil forced air natural, Oil forced air natural, Oil forced water forced. 

The winding & CORE are both MADE of METALS and so an insulation have to be placed in between them, the thickness of insulation depends on the voltage rating of the winding. In order to reduce the insulation requirement the LOW voltage winding place near the core. 

The winding & Core are both made of metals and so an insulation have to be placed in between them, the thickness of insulation depends on the voltage rating of the winding. In order to reduce the insulation requirement the low voltage winding place near the core. 

It is LOCATED between TRANSFORMER TANK and CONSERVATOR.

It is located between transformer tank and conservator.

It protects the transformer from their INTERNAL faults LIKE earth faults, winding SHORT circuit, short circuit between phases, Puncture of bushing etc.

It protects the transformer from their internal faults like earth faults, winding short circuit, short circuit between phases, Puncture of bushing etc.

A conservator is a SMALL cylindrical drum fitted just above the transformer main tank. It is used to allow the expansion and CONTRACTION of oil without CONTACT with surrounding atmosphere. When conservator is fitted in a transformer, the tank is FULLY filled with oil and the conservator is HALF filled with oil.

A conservator is a small cylindrical drum fitted just above the transformer main tank. It is used to allow the expansion and contraction of oil without contact with surrounding atmosphere. When conservator is fitted in a transformer, the tank is fully filled with oil and the conservator is half filled with oil.

When transformer OIL is USED as a coolant the HEAT dissipation by convection is 10 TIMES more than the convection due to air. Hence transformer oil is used as a cooling medium.

When transformer oil is used as a coolant the heat dissipation by convection is 10 times more than the convection due to air. Hence transformer oil is used as a cooling medium.

Transformer oil provides:

1. good insulation and
2. cooling .

Nowadays INSTEAD of natural mineral oil, SYNTHETIC oils known as ASKRELS (trade name ) are used. They are non-INFLAMMABLE, under an electric arc do not DECOMPOSE to produce inflammable gases. PYROCOLOR oil possess HIGH dielectric strength.

Transformer oil provides:

Nowadays instead of natural mineral oil, synthetic oils known as ASKRELS (trade name ) are used. They are non-inflammable, under an electric arc do not decompose to produce inflammable gases. PYROCOLOR oil possess high dielectric strength.

The silica GEL is USED to ABSORB the moisture when the AIR is drawn from the atmosphere in to the transformer.

The silica gel is used to absorb the moisture when the air is drawn from the atmosphere in to the transformer.

1. Saving in iron MATERIAL
2. SMALL SIZE
3. Less transformer oil
4. Economical
5. HIGHER EFFICIENCY

1. CONTINUITY of SUPPLY
2. LESS INSTALLATION of cost
3. Easy transportation
4. Stand by function
5. Unbalanced load supply

A transformer bank consists of three INDEPENDENT single PHASE transformers with their PRIMARY and SECONDARY windings CONNECTED either in star or delta.

A transformer bank consists of three independent single phase transformers with their primary and secondary windings connected either in star or delta.

It is the RATIO of COPPER AREA in the WINDOW to the TOTAL window area.

It is the ratio of copper area in the window to the total window area.

• Require LESS conductor material
• low COST
• low SIZE
• high VA rating
• high EFFICIENCY
• Better voltage regulation
• SMALL amount of no load current 

1. As a BOOSTER to COMPENSATE the VOLTAGE drop for better regulation
2. As induction motor STARTERS.
3. In locomotive
4. As FURNACE transformer 

If the PHASE sequence is in an INCORRECT MANNER, in EVERY cycle each pair of phases will get short-circuited.

If the phase sequence is in an incorrect manner, in every cycle each pair of phases will get short-circuited.

A difference in the ratio of the reactance value to resistance value of the per UNIT impedance results in a different phase angle of the currents carried by the TWO paralleled transformers; one TRANSFORMER will be WORKING with a higher power factor and the other with a lower power factor than that of the combined OUTPUT. Hence, the real power will not be proportionally shared by the transformers.

A difference in the ratio of the reactance value to resistance value of the per unit impedance results in a different phase angle of the currents carried by the two paralleled transformers; one transformer will be working with a higher power factor and the other with a lower power factor than that of the combined output. Hence, the real power will not be proportionally shared by the transformers.

Two transformers in Parallel should have the same primary and secondary voltage RATINGS. Any ERROR in the voltage ratio would cause heavy circulating currents to FLOW between the transformers. This circulating current will RESULT in a corresponding imbalance in the primary currents, and result in overloading of one transformer. This circulating current will result in increased copper losses.

Two transformers in Parallel should have the same primary and secondary voltage ratings. Any error in the voltage ratio would cause heavy circulating currents to flow between the transformers. This circulating current will result in a corresponding imbalance in the primary currents, and result in overloading of one transformer. This circulating current will result in increased copper losses.

CONNECTING transformers with WRONG polarity can result in CIRCULATING currents or short circuits.

Connecting transformers with wrong polarity can result in circulating currents or short circuits.

• Equal polarity
• Equal TURN ratio
• percentage IMPEDANCE should be same
• Equal X/R ratio
• Equal KVA RATING
• Equal PHASE sequence.

• Non availability of SINGLE large transformer to meet the load
• Increased power demand
• To IMPROVE reliability
• If many SMALLER transformer is USED one can be used as SPARE
• Transportation problem for large transformer.

EFFICIENCY as WELL as TEMPERATURE RISE of WINDING.

Efficiency as well as temperature rise of winding.

COPPER LOSS.

Copper loss.

The open circuit on a TRANSFORMER is conducted at a rated voltage because core LOSS depends upon the voltage. This open circuit test gives only core loss or IRON loss of the transformer.

The open circuit on a transformer is conducted at a rated voltage because core loss depends upon the voltage. This open circuit test gives only core loss or iron loss of the transformer.

The RATED current is less on HV SIDE. This will also permit to use ammeter and WATTMETER of lower current RANGE.

The rated current is less on HV side. This will also permit to use ammeter and wattmeter of lower current range.

The high-voltage side is generally KEPT OPEN because the current in high-voltage winding is less COMPARED to that on low-voltage winding.The LV side has higher current so that MAXIMUM no load current can be measured.

The high-voltage side is generally kept open because the current in high-voltage winding is less compared to that on low-voltage winding.The LV side has higher current so that maximum no load current can be measured.

IRON LOSS.

Iron loss.

• Direct loading test
• OPEN circuit test
• Short circuit test
• SUMPNER's or back to back test

It is computed on the basis of ENERGY consumed during a CERTAIN period, usually a day of 24 HRS. All day efficiency=output in kWh/input in kWh for 24 hrs.

It is computed on the basis of energy consumed during a certain period, usually a day of 24 hrs. All day efficiency=output in kWh/input in kWh for 24 hrs.

When IRON LOSSES is EQUAL to COPPER losses.

When Iron losses is equal to copper losses.

COPPER LOSS of a transformer DEPENDS on current and iron loss on VOLTAGE . HENCE total losses depends on Volt- Ampere and not on the power factor. That is why the rating of transformers are in kVA and not in kW.

Copper loss of a transformer depends on current and iron loss on voltage . Hence total losses depends on Volt- Ampere and not on the power factor. That is why the rating of transformers are in kVA and not in kW.

Iron losses depend on SUPPLY frequency and flux density in the core. For all NORMAL operations, the frequency of flux REVERSALS which is same as supply frequency is constant and the value of flux density more or less REMAINS constant. Hence iron losses remain constant under all load conditions. i-e from no-load to full-load.

Iron losses depend on supply frequency and flux density in the core. For all normal operations, the frequency of flux reversals which is same as supply frequency is constant and the value of flux density more or less remains constant. Hence iron losses remain constant under all load conditions. i-e from no-load to full-load.

By USING GOOD MAGNETIC material.
By using less VALUE of Magnetic flux DENSITY.

By using good magnetic material.
By using less value of Magnetic flux density.

The magneto motive force or mmf APPLIED in the transformer core is alternating. For every CYCLE due to this domain reversal, there will be extra work DONE. For this reason, there will be a consumption of electrical energy which is known as HYSTERESIS loss of transformer.

The magneto motive force or mmf applied in the transformer core is alternating. For every cycle due to this domain reversal, there will be extra work done. For this reason, there will be a consumption of electrical energy which is known as Hysteresis loss of transformer.

By USING less thickness of laminations
By using less value of MAGNETIC FLUX DENSITY

By using less thickness of laminations
By using less value of Magnetic flux density

In transformer, we supply alternating current in the primary, this alternating current produces alternating magnetizing flux in the core and as this flux links with secondary winding, there will be induced voltage in secondary, resulting current to flow through the load connected with it. Some of the alternating fluxes of transformer; may also link with other conducting parts LIKE steel core or IRON body of transformer etc. As alternating flux links with these parts of transformer, there would be a locally induced emf. Due to these emfs, there would be currents which will circulate locally at that parts of the transformer. These CIRCULATING current will not contribute in output of the transformer and dissipated as heat. This TYPE of energy loss is called eddy current loss of transformer.

In transformer, we supply alternating current in the primary, this alternating current produces alternating magnetizing flux in the core and as this flux links with secondary winding, there will be induced voltage in secondary, resulting current to flow through the load connected with it. Some of the alternating fluxes of transformer; may also link with other conducting parts like steel core or iron body of transformer etc. As alternating flux links with these parts of transformer, there would be a locally induced emf. Due to these emfs, there would be currents which will circulate locally at that parts of the transformer. These circulating current will not contribute in output of the transformer and dissipated as heat. This type of energy loss is called eddy current loss of transformer.

• Load current
• EQUIVALENT resistance 
• Equivalent reactance 
• POWER FACTOR

It OCCURS when load is INDUCTIVE and power FACTOR is LAGGING.

It occurs when load is inductive and power factor is lagging.

Negative SIGN indicates zero voltage regulation. It OCCURS when load is capacitive and POWER factor is LEADING.

Negative sign indicates zero voltage regulation. It occurs when load is capacitive and power factor is leading.

No-load CURRENT produces FLUX and supplies IRON loss and COPPER loss on no-load.

No-load current produces flux and supplies iron loss and copper loss on no-load.

1. There should be no losses
2. The winding should have zero resistance
3. The leakage FLUX should be zero
4. The PERMEABILITY of core should be so high that the negligible CURRENT is REQUIRED to establish the flux in it.