1. Transformer magnetic circuits are made of : electrical steel

2. Magnetic circuits of the transformers are made of ferromagnetic materials because: have high magnetic permeability

3. The magnetic circuit of the transformer runs as transformer iron because: reduce eddy current losses

4. Transformer windings are made of materials having: relatively resistivity low

5. The electrical circuits (windings) of transformer runs from : copper or aluminum

6. Which of the electrical parameters of an electrical transformer remains unchanged: frequency

8. The electrical transformer is a static device with two or more magnetically coupled windings, which transforms: under the law of electromagnetic induction - electrical parameters (voltage, number of phases) of electricity into alternating current, the frequency remains unchanged;

9. The electrical transformer is built from the following basic building blocks : ferromagnetic core and windings System

10. A ferromagnetic core made: a close magnetic coupling between the electrical circuits of windings;

11. Which of the following applied currents to transformer primary produce magnetic field Primary current

12. Which of the three materials are used along the ferromagnetic core: Copper, steel and electrical insulating materials

13. Which of the following is not a necessary element in the operation of the transformer: electrostatic force

14. Which of the following defines the action of the transformer: Electromagnetic power transferred from primary to secondary

15. What are the electrical quantities that change from a transformer secondary to primary: Voltage and current

16. Why are made of ferromagnetic core laminations of transformers of siliceous high alloy sheet To minimize eddy current losses

17. What are the major differences between primary and secondary windings of a transformer Primary winding is connected to the power supply and the secondary to the load

18. How cool the small power transformers In air by free convection

19. How to call transformer windings by the relative magnitude of the voltage High voltage and low voltage

20. How are divided by the number of phase transformers Phase and polyphase, the most common being the three-phase transformers

21. Which of these three elements are submitted on the rating plate (label) Nominal power, nominal voltages, nominal currents of line, number of the phases

22. What are the main structural elements of the ferromagnetic core transformer Columns and yokes

23. How are wound windings of large power transformers? On a ferromagnetic material housing

24. What transforms the active power losses in the active elements of the transformer Heat

25. What is the name elements denoted by 1 and 2 of mono-phase transformer from Fig. T1. 1 - primary winding 2 - secondary winding

26. What is the name elements denoted by 3 si 4 of mono-phase transformer from Fig. T 1. 3- generator (source ) 4-load (consummator)

27. What is the name of the element denoted by 5-of the mono-phase transformer from Fig. T 1. 5- ferromagnetic core

29. The report of the voltage across the two windings, denoted ku has a value

2

1

2

1

w

w

u

uku

30. Self inductance of the transformer primary winding is defined as : The ratio of the total flow going through the winding and the current which across the winding

31. Relationship 1 11111

wL

i

is:

Self inductance; 32. The mutual inductance depends on :

Its coils and the coils of the winding which is magnetically coupled; 33. The armature reaction to a transformer is expressed by the relation:

1 1 2 2wi w i ;

34. Which of the electrical parameters of an electrical transformer remains unchanged: The frequency;

35. Between the primary and secondary windings of a power transformer must be: A tight magnetic coupling (good)

36. To reduce eddy current losses can act

Reducing the thickness of the sheet and increasing resistivity magnetic material , an effect that is obtained by alloying silicon steel;

37. Why are made of ferromagnetic core laminations of the transformers by siliceous high alloy sheet? To minimize eddy current losses

38. What are the electrical quantities that change from a secondary winding to primary winding? The voltage and current

39. Which of the following defines the action of the transformer? The transfer of electric power on electromagnetic away from the primary winding to secondary winding

40. Which of the following is not a necessary element in the operation of the transformer? electrostatic force

42. Who produces magnetic flux that causes voltage in secondary winding primary current

43. What magnetic flux induces in the transformer secondary the emf E2 the useful magnetic flux

44. Which of the following statements concerning the transformation ratio of a transformer is true is directly proportional to the number of turns in the primary and inversely proportional to the number of turns in the secondary

45. What is the transformation ratio of a transformer if voltage applied at the primary winding is mayor 400V, and the voltage applied secondary winding is 200V? 2

1. What are the windings of a DC-machines? Excitation winding, pole auxiliary winding and winding compensation

2. What is the role of auxiliary poles in the building of DC machine? The auxiliary poles are designed to produce a specific magnetic field conducting improve switching DC machine.

3. What are the basic constructive elements of a DC machine ? housing, excitation poles and auxiliary poles, brush system - brush, terminal box, side shields or covers ferromagnetic core rotor, rotor winding, collector and fan blades.

4. What is the role of the main poles in building of DC machine? main poles mainly produce in machine the field excitation

6. What is the rotor of a DC-machines? The rotor contains core contains magnetic rotor rotor winding and machine shaft

7. What is the collector? The collector is a mechanical rectifier, which aims to transform alternative emf from the rotor sections in a DC voltage

8. What are the brushes, brush holders and collar support and their role? the brushes, brush holders and collar support are the set of pieces that makes the link between the rotor of the machine and fixed part