WAZIPOINT Engineering Science & Technology: Transformer Introduction and FAQ: Frequently Asked Question of a Transformer

Monday, June 13, 2022

Transformer Introduction and FAQ: Frequently Asked Question of a Transformer


Transformer Introduction and FAQ
Major Parts of an Electrical Transformer

FAQ of an Electrical Transformer

Introduction of a Transformer

A transformer is a static electrical machine used to change the voltage of alternating current that has the same frequency. Before going to details on the electric transformer, types of transformers,  parts of transformer, construction of a transformer, step-up transformer, voltage transformer, current transformer and transformer equation, we would like to understand-

The basic principle of transformer

A transformer is a static machine (STATIC MACHINE) that is used to convert the alternating current potential at the same frequency (TRANSFER), that is, a transformer with low-voltage to strong alternating current in high-voltage weak current, or high-voltage weak Transmits the current at a frequency similar to that given in a strong electric current of low voltage.

The transformer's working principle is based on the static induction principle.

In fact, a transformer is made up of a magnetic circuit consisting of two characteristic windings called PRIMARY windings and SECONDARY windings. When the primary coil is connected to the alternating current supply (AC SUPPLY), the alternating flux is formed in the plated core and when the flux is connected (LINKING) to the secondary coil, a reversible force (EMF) is induced in the secondary coil. 

This action is caused by induction between the two coils due to the alternating flux, even in the primary coil, the SELF INDUCTION is induced by the force. If the flux is completely connected to each revision of both the spheres then the value of the induced V, VA, the force will be exactly the same at each moment. Thus the induced force in the secondary coil will be in the opposite phase of the APPLIED VOLTAGE used in the primary winding (assuming the resistance of the coil is neglected). 

The electrical carrying force induced in the secondary winding depends on the number of turns (wrap around the wire) of the secondary coil. When the number of turns in the secondary coil is greater than the primary coil when the induced force in the secondary coil is greater than the voltage used in the primary coil.

Main Parts of a Transformer

The transformer consists of the following main parts

Core - The main function of the core is to flow the magnetic path for the pole flux and to support the transformer winding.

Windings - Transformer winding is of the following two types

(i)Primary Winding;
(ii) Secondary Winding.

These are mainly conductors who are the best driver and the winding is done by that driver. Transformer winding mainly depends on the winding turn. The primary winding is that to which we supply the supply voltage. And the second winding is the one we put the load on.

Insulation - Insulation is that through which current does not flow. Electrification is used in transformers so that both windings can be electrically insulated from each other which is used between different layers.

FAQ for a Transformer

Question 1 - Can the transformer be ignited in the direction (DC)?
Answer - Transformer cannot be mounted on direct current. If the primary winding of the transformer is connected to the direct current, the flux will be generated in the coil but it will not increase or decrease, but will remain unchanged and hence no current will be induced in the second coil (supply Except when awhile). Thus the direct current voltage cannot be increased or decreased with the help of a transformer. Conversely, connecting the transformer with direct current voltage can cause damage. Because by doing this, no lagging force will be induced in the primary coil of the transformer, due to which the primary coil will be heated by taking more current from the supply and the primary coil will burn.

Question 2: The rating of the transformer is always written in KVA (kilo volt-ampere, while the motors are given in K.W. or H.P.
Answer: The reason is that the power factor of the transformer always depends on the machines or other loads on it, whereas the determination of induction motors (induction motor) is always K.W. Or written in H.P. because their power multiplier depends on their own load.

Question 3- Can the transformer be run at a higher or lower frequency than the specified frequency at the specified voltage?
| Answer - The transformer can be run at a higher frequency than the specified frequency, but in this case, the core will have a lower flux density and the magnetizing current will be lower, thus lowering the load of the transformer for the same KVA out at higher frequency Can downsize

Conversely, the transformer should not operate at a frequency lower than the prescribed frequency at the specified voltage. At low frequency, the core will become highly saturated, which will cause the magnetization current to become excessive and thus increase the iron losses, causing the core to overheat and burn to the coil.

For this, if you ever want to decrease the frequency, then the voltage used in the same ratio should also be reduced so that the flux density remains the same. In such a situation the iron losses will be the same but the output of the transformer will also decrease when the voltage is low.

Brief question and answer regarding the Transformer

Question 1. What do you understand about the transformer?
Answer - It is a stationary machine used to reduce or increase the voltage.

Question 2. On which rule does the transformer operate?
Answer - On Mutual Induction.

Question 3. What are the main parts of a transformer?
Answer - Primary Winding, Secondary Winding, Core

Question 4. What is the name of the winding in which the supply is given?
Answer: Primary Winding

Question 5. What is the name of the winding from which the supply is taken?
Answer - Secondary Winding.

Question 6. What is the advantage of the laminated core?
Answer - Reduces EDDY CURRENT LOSS in the core.

Question 7. How many magnetic paths are there in a core type transformer?
Answer - One.

Question 8. How many magnetic paths are there in a shell type transformer?
answer me.

Question 9. What do you understand by the transformer ratio?
Answer - E2 / E1 = N2 / N1 = I1 / I2

Question 10. Give the formula of EMF generated in the winding of the transformer.
Answer - E = 4.44Φmaxf N Volts

Question 11. Why is the transformer oil filled in the transformer?
Answer - To increase insulation and cool the windings.

Q12. What do you understand by flashpoint of transformer oil?
Answer: Ignition point of oil vapour

Q13. What do you understand by flashpoint of transformer oil?
Answer - The temperature at which oil catches fire.

Question 14. Why is Breather fitted in a transformer?
Answer - To deliver dry air to the transformer.

Q 15. Why is there a conservator above the transformer?
Answer: When the oil is heated and spreads, it gives it a place.

Question 16. What material is filled in Breather?
Answer: Calcium chloride or silica jelly 

Question 17. What is an emergency release?
Answer - There is a pipe above the transformer which protects the transformer from bursting during the short circuit.

18. What is the relationship between no-load flux and load flux?
Answer - The function which is on load is the same on load.

Question 19. What are the functions of no-load current in a transformer?
Answer - produces flux and compensates iron and copper loss.

Q 20. What is the effect on the primary when the load is increased on the secondary side?
Answer - Current increases in the primary.

Question 21. Which test is done to find iron loss?
Answer - Open Circuit Test.

Question 22. Which test is done to find copper loss?
Answer - Short Circuit Test.

Question 23. Why leave copper loss in open circuit test?
Answer - Due to the low load current.

Question 24, Why do short circuits leave iron loss in the test?
Answer - Because primary winding has very low voltage and is proportional to iron loss voltage (flux).

Question 25, Why are autotransformers used at low voltage only?
Answer - Because the primary and secondary are of the same winding.

Question 26. What are the main benefits of autotransformers?
Answer - Copper (copper) saving.

Question 26. What are the main benefits of autotransformers?
Answer - Copper (copper) saving.

Question 27. What do you understand by CT and PT?
Answer - CT is called current transformer which is used to measure more current. It is called PT (potential transformer) which is used to measure high voltage (at H.T.).

Question 28. Tell the range of current and voltage above which CT and PT are used?
Answer - 60 A, 750 V

Question 29. What are the precautions to be taken while separating ampere meter from CT?
Answer - There should be a secondary short.

Test Yourself about Transformer choosing the correct answer from the following questions for an electric trial Transformer

1. Phase difference between primary and secondary voltages of a transformer
(a) 90 °
(b) 0o
(c) 180 °
(d) Between 30 ° and 60 °

2. The output-input measurement method is difficult to determine the efficiency of a transformer because
(a) The output is sinusoidal and cannot be measured.
(b) The efficiency of the transformer is generally very high and hence the need for very pure measuring
it occurs.
(c) Losses are abnormally high.
(d) Output is out of phase compared to input.

3. A transformer has full load iron loss 900 W and copper loss 1600 W. At what% load will the transformer give maximum efficiency?
(a) 100%
(b) 50%
(c) 75%
(d) 90%

4. Which stage is necessary to run the transformers in parallel?
(a) They should have the same kVA rating.
(b) They should be run at the same frequency.
(c) Their voltage rating should be in proportion to the load sharing
(d) Their transformation ratio should be according to the ratio of load sharing

5. Chemicals used in the transformer's breeder
(a) salt
(b) water
(C) Mineral Cool
(d) Silica water

6. What losses in transformers change with load?
(a) Copper losses
(b) core losses
(C) Eddy current losses
(d) Hysteresis losses

7. Which part of the transformer generates the most heat?
(a) core
(b) frame
(C) Oil
(d) winding

8. If the flux density in the core of a transformer is increased
(a) AD current losses will be less
(b) The wave size of the secondary side will be disturbed.
(c) Transformer size can be reduced.
(d) The frequency of secondary winding will change

9. Always in primary and secondary coils of the transformer
(a) The wire has the same size
(b) The number of rounds varies.
(c) Magnetic circuit is the same
(d) Magnetic circuit is different.

10. By doing open circuit test on transformer
(a) Copper losses are obtained.
(b) Eddy current losses are obtained.
(c) The sum of hysteresis and eddy current losses is obtained.
(d) Hysteresis losses.

11. A transformer has the condition to achieve maximum efficiency
(a) Copper losses = Iron losses
(b) Core losses = hysteresis losses
(C) Hysteresis losses = AD current losses
(d) Total losses = x copper losses

12. The function of the breeder of the transformer is
(a) To filter transformer oil.
(b) Management of cold air.
(C) To provide oxygen to the cooling oil.
(d) When the air from outside enters the transformer, the moisture from the air has to be absorbed.

13. Transformer's e.m.f. What does the value depend on?
(a) Frequency, number of turns, and equal to the flux
(b) Equal to the square and frequency of the number of turns
(c) Equal to the number of turns and square of the frequency
(d) Number of turns, frequency, and square of flux equal

14. Step, Number of turns in primary winding in down transformer, the number of turns in the secondary winding
(a) will be less.
(b) will be more.
(C) will be equal
(d) One turn will be less.

Answer number 1. (c), 2. (b), 3. (c), 4. (b), 5. (d), 6. (a), 7. (d), 8. (c), 9 . (C), 10. (C), 11. (a), 12. (d), 13. (a), 14. (b)

You may know the details about the electrical transformer from the following articles:

  1. Working Principle of Transformer;
  2. Transformer Construction;
  3. Core-type Transformers;
  4. Shell-type Transformers;
  5. Elementary Theory of an Ideal Transformer;
  6. E.M.F. Equation of Transformer;
  7. Voltage Transformation Ratio;
  8. Transformer with losses but no Magnetic Leakage;
  9. Transformer on No-load;
  10. Transformer on Load;
  11. Transformer with Winding Resistance but no Magnetic Leakage;
  12. Equivalent Resistance;
  13. Magnetic Leakage;
  14. Transformer with Resistance and Leakage Reactance;
  15. Simplified Diagram;
  16. Total Approximate Voltage Drop in Transformer;
  17. Exact Voltage Drop;
  18. Equivalent Circuit Transformer Tests;
  19. Open-circuit or No-load Test;
  20. Separation of Core Losses;
  21. Short-Circuit or Impedance Test;
  22. Why Transformer Rating in KVA?;
  23. Regulation of a Transformer;
  24. Percentage Resistance, Reactance, and Impedance;
  25. Kapp Regulation Diagram;
  26. Sumpner or Back-to-back-Test;
  27. The efficiency of a Transformer;
  28. Condition for Maximum Efficiency;
  29. Variation of Efficiency with Power Factor;
  30. All-day Efficiency;
  31. Auto-transformer;
  32. Conversion of 2-Winding Transformer into Auto-transformer;
  33. Parallel Operation of Single-phase Transformers;
  34. Questions and Answers on Transformers;
  35. Three-phase Transformers;
  36. Three-phase Transformer Connections;
  37. Star/Star or Y/Y Connection;
  38. Delta-Delta or ∆/∆ Connection;
  39. Wye/Delta or Y/ Connection;
  40. Delta/Wye or ∆/Y Connection;
  41. Open-Delta or V-V Connection;
  42. Power Supplied by V-V Bank;
  43. Scott Connection or T-T Connection;
  44. Three-phase to Two-Phase Conversion and vice-versa;
  45. Parallel Operation of 3-phase Transformers;
  46. Instrument Transformers;
  47. Current Transformers;
  48. Potential or Voltage Transformers.

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