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A common method of cooling a power transformer is oil cooling.

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Answer : Natural oil cooling is used for transformers up to a rating of 3000 kVA.

Answer : Natural air cooling is generally restricted for transformers up to 1.5 MVA .

Description : State the function of cooling tower and condenser in thermal power station.

Answer : 1. Condenser:   Function of condenser is to convert exhaust steam again into water by reducing its temperature with the help of cold water. Also it reduces back pressure of steam turbine 2 ... tower : The function of cooling tower is to reduce the temperature of water coming from condenser.

Description : Draw and explain the function of cooling tower in TPS.

Answer : Cooling tower in TPS: The function of cooling tower is to reduce the temperature of water coming from condenser. Water is circulated from the basin of the cooling ... cooling Tower temperature of water is reduced either by natural or forced or induced draught method or combine

Description : Which of the following is used for thermoelectric cooling? A) Peltier effect B) Seebeck effect C) Both A and B D) None of these

Answer : Which of the following is used for thermoelectric cooling? A) Peltier effect B) Seebeck effect C) Both A and B D) None of these

Answer : Harmonics in transformer result in increased core losses, increased I2R losses, and magnetic interference with communication circuits.

Answer : Power transformers are generally designed to have maximum efficiency around near full-load.

Description : The efficiencies of transformers compared with that of electric motors of the same power are?

Answer : Transformers have high efficiency than the same ratted motors

Description : If the percentage impedances of the two transformers working in parallel are different, then?

Answer : If the percentage impedances of the two transformers working in parallel are different, then parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load.

Answer : Distribution transformers are generally designed for maximum efficiency around 50% load.

Description : Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in?

Answer : Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in loading of the transformers not in proportion to their kVA ratings.

Answer : Short circuit test on transformers is conducted to determine copper losses.

Answer : Necessary conditions required to be satisfied in order to ensure successful parallel operation of single phase transformers:  1. Only transformers having the same phase displacement between primary and secondary ... . 7. The phase sequence must be followed strictly on HV and LV side connection.

Description : Losses which occur in rotating electric machines and do not occur in transformers are?

Answer : Friction losses windage losses 

Description : The efficiency of two identical transformers under load conditions can be determined by?

Answer : The efficiency of two identical transformers under load conditions can be determined by back-to-back test.

Description : State any two conditions for parallel operation of 3-phase transformer.

Answer : Conditions for Parallel operation of 3 phase transformer 1) Voltage ratings of both the transformers must be identical. 2) Percentage or p.u. impedance should be equal in magnitude. 3) X/R ratio ... between primary & secondary voltages must be same. 6) Phase sequence on both sides must be same.

Description : Compare core type transformer and shell type transformer on the following parameters. (i) Types of winding used, (ii) Application

Answer : Ans:

Description : Define: (i) Commercial efficiency of a transformer and  (ii) All day efficiency of a transformer.

Answer : (i) Commercial Efficiency : It is the ratio of output power in watt to the input power in watt. (ii) All day efficiency of a transformer: It is the ratio of output energy in kWh to the input energy in kWh in the 24 hours of the day

Description : A 50 KVA transformer has iron loss 2 kW on full load. Calculate its iron loss at 75% of full load.

Answer : Iron loss is dependent on voltage and independent of load. Hence iron loss at 75% of Load = Iron loss at full load = 2 kW

Description : State any four properties of Ideal transformer.

Answer : Properties of Ideal transformer: 1) No losses (iron and copper losses), hence no temperature rise. 2) No magnetic leakage i.e (Coefficient of coupling between primary and secondary windings is unity) 3) Zero winding ... drop i.e. E1 = V1, E2 = V2 5) Efficiency 100 %. 6) Regulation 0 %.

Description : Why circuit breaker connect b)w two transformer  (same rating

Answer : Because two transformers connection is in parallel to share the load if any transformer is receives the surge current because of the fault so to protect the other transformer from the fault. 

Description : Classify the transformers based on the construction, frequency and power.

Answer : Classification of Transformer Based On: i) Construction: Shell type, Core type, Berry type ii) Change in voltage level: Step-Up, Step-Down, iii) Number of phases: Single phase, Three phase iv) ... Control vi) Cooling: Self-cooled, Air-cooled, Forced-air cooled, Oil-cooled, Forced-oil cooled. 

Description : State any two applications of single phase autotransformer.

Answer : Applications of single phase auto transformers: 1) Give small boost to distribution cable to correct the voltage drop. 2) As auto transformer starter for induction motors. 3) As furnace supply ... . 5) In control equipment for single phase locomotives. 6) As dimmer in lighting circuits.

Description : Define transformation ratio in terms of current and voltage.

Answer : (i) Transformation Ratio (K) is defined as the ratio of the primary current to the secondary current.  (ii) Transformation Ratio (K) is defined as the ratio of the secondary voltage to the primary voltage.

Description : Draw the connection diagram of long shunt differential D.C. compound generator.

Answer : Ans:

Description : Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary

Answer : Which of the following connection of transformers will give highest value of secondary voltage ? (A) Delta primary delta secondary (B) Delta primary star secondary (C) Star primary star secondary (D) Star primary delta secondary

Description : Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by 

Answer : Two transformers A and B having equal outputs and voltage ratios but unequal percentage impedances of 4 and 2 are operating in parallel. The transformer A will be overloaded by 33%

Description : Core type transformers are popular in___________.  (A) High voltage applications (B) Low voltage applications (C) All of the above (D) None of the above

Answer : Core type transformers are popular in High voltage applications

Description : In a transmission line if booster transformers are to be used, preferred location will be  (A) At the receiving end (B) At the sending end (C) At the intermediate point (D) Anywhere in the line 

Answer : In a transmission line if booster transformers are to be used, preferred location will be At the intermediate point

Description : The friction losses in Real Transformers are :  (A) 0% (B) 5% (C) 25% (D) 50%

Answer : A

Description : Two 3-phase transformers cannot be operated in parallel, if their :  (A) kVAs are different (B) phase sequences are different (C) % impedances are different (D) voltage ratios are different

Answer : Two 3-phase transformers cannot be operated in parallel, if their : phase sequences are different

Description : An additional condition for parallel operation of three-phase transformers over single-phase transformers is that

Answer : An additional condition for parallel operation of three-phase transformers over single-phase transformers is that the transformers should belong to the same vector group

Description : Which of the following is the advantage of using CRGO steel in transformers? A) High magnetic flux density B) Low permeability C) Both A and B D) None of these

Answer : It definitely High Magnetic Flux Density since a crgo steel has always a more around 3% of silicon proportion among the remaining ferrite which make cold rolled grain oriented steel having high flux magnetic ... for more about the crgo core you can learn here https://nicoreindia.com/crgo-core/

Answer : Instrument transformers are potential transformers, current transformers.

Description : What is the back EMF in Transformers?

Answer : Current transformers (CT) : Current transformer (CT) actually step down the high current to low current for the operation of relays. Current transformer is use for measurement of ... use for relay. This is about potential transformer.

Description : Why do transformers make noise?

Answer : Transformers make noise based on it out put if an transformer outputs is 400v maximum than a 398v be apply to that transformer it also make a noise because of that 

Description : Three phase step-up transformer installed at power house, just before commencement of transmission line, have:

Answer : Three phase step-up transformer installed at power house, just before commencement of transmission line, have: star delta connections

Description : A simple phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is  (A) 86.7% (B) 88.26% (C) 88.9% (D) 87.8%

Answer : A simple phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is 87.8%

Description : In a power transformer, the fundamental frequency of the hum arising due to magnetostriction is  (a) equal to the line frequency (b) double the line frequency (c) 4 times the line frequency (d) not related to the line frequency

Answer : In a power transformer, the fundamental frequency of the hum arising due to magnetostriction is double the line frequency

Description : In a step-up or step-down transformer, electrical power is transferred from one circuit to another without change in

Answer : In a step-up or step-down transformer, electrical power is transferred from one circuit to another without change in frequency

Answer : The efficiency of a power transformer is of the order of 98 percent.

Answer : The power transformer is a constant main flux device.

Answer : In a power or distribution transformer about 10 percent end turns are heavily insulated to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns.

Description : The maximum load that a power transformer can carry is limited by its?

Answer : The maximum load that a power transformer can carry is limited by its voltage ratio.

Description : _______ electric power is the most common method used by electrical grids to transfer power.  (A) One-phase (B) Two-phase (C) Three-phase (D) None of the above

Answer : Three-phase electric power is the most common method used by electrical grids to transfer power. 

Description : Classify I. C. Engine on the basis of -Cycle of operation -Method of cooling

Answer : Classification of I. C. Engine on the basis of  -Cycle of operation: a) Otto cycle engine b) Diesel cycle engine c) Duel combustion engine or semi-diesel cycle engine -Method of cooling: a) air cooled engine b) water cooled engine 

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