How many steps are needed for the resistance to be shorted out in a magnetic starter

13.03.18= 4 семестр 2018 ( группа Э-325 СН) З /О АВИЭТ

(2 –ВЕСЕННИЙ - СЕМЕСТР)                                                                 КОНТРОЛЬНАЯ РАБОТА ВАРИАНТ 2

TASK  1 CHOOSE THE CORRECT FORM:

1. The teacher insists on our ……….the work on time.

 1. doing 2. having done 3. having been done 4. Done

2. She knows of his ……. at the exam.

1. failing 2. failed 3. having failed 

3. They rely on your ……… the work properly.

1. doing 2. having been done 3. having done 4. Done

4. I am sure of his ….. the exam successfully.

1. passing 2. Having passed

5. The book is worth……….

1. reading 2. having read 3. having been read 4. Read

6. We insist on the lecture on applied mechanics ……...

1. delivered 2. having delivered 3.having been delivered 4. delivering

7. They discussed different ways of......

1. the problem can be solved 2. solving the problem 3. the problems are usually solved

8. I don t mind ……. 1. applying the algebraic method 2. they applied

the algebraic method 3.before they apply the algebraic method

9. He denied my ……. him before.

1. seeing 2. having seen

 

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13.03.18= 4 сем. 2018 ( Э -325 СН ) З / О АВИЭТ ВАРИАНТ 2

10. The designer wanted ….. the stability of the apparatus.1. increased 2. to increase 3.increased 4. having increased

11. Newton was the first ….. the problem.

1.solve 2. solved 3. solves 4. to solve

12. Students …… foreign literature should read special literature in the original.

1. studying 2.having been studied 3. studied 4. having studied                                                   

13. “ Lines of forces” are known ……..by Faraday.

1. were introduced 2. Introduced 3. to have been introduced

14. The professor wanted the students …. the principle of Archimedes.

1. stating 2. stated 3. to state 4. will state

15. I m waiting for my friend …….back.

1. comes 2. to come 3. has come 4. is coming

16. She heard him … the door.

1. open 2. to open 3. opens 4. Opened

17. This compound seems … some valuable properties.

1. having 2. to have 3. have 4. Has

18. He tells us …him at the airport.

1. meet 2. to meet 3. Meeting

19. My room-mate asked me …… making noise.

1. stop 2. stopping 3. to stop

20. The book is said ….. very interesting.

1. being 2. having been 3. to be

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13.03.18= 4 сем. 2018 (Э-325 СН) З /О АВИЭТ ВАРИАНТ 2                                    

21…… in Moscow for ten years I moved to Kiev.

1. having lived 2. While living

22. …. new problems scientists do a lot of research.

1. when solving 2. having solved 3. solved 4. having been solved

23. I don t like the idea of ……. this theme at the next lesson.

1. discussing 2. having discussed 3. having been discussed 4. Discussed

24. The professor wanted the students …. the principle of Archimedes.

1. stating 2. stated 3. to state 4. will state

25. I m waiting for my friend …….back.

1. comes 2. to come 3. has come 4. is coming

26. She heard him … the door.

1. open 2. to open 3. opens 4. Opened

27. This compound seems … some valuable properties.

1. having 2. to have 3. have 4. Has

1. meet 2. to meet 3. Meeting

28. My room-mate asked me …… making noise.

1. stop 2. stopping 3. to stop

29. The book is said ….. very interesting.

1. being 2. having been 3. to be

30. He tells us …him at the airport.

1. meet 2. to meet 3. Meeting

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13.03.18= 4 сем. 2018 ( Э -325 СН ) З / О АВИЭТ ВАРИАНТ 2                                     -TASK 2 TRANSLATE THE TEXTS AND ANSWER THE QUESTIONS:

TEXT 1 SYNCRONOUS MOTORS

Syncronous  motors characteristically operate at constant speed, independent of load.Speed is directly proportional to the line frequency of the power supply and inversely proportional to the number of poles in the stator or rotor.

The motors are made in all sizes – from subfractional-horse power, non-excited units to large-horsepower, direct-current-excited motors for industrial drives. Their electrical input may vary from a few watts, as in the case of electric clocks and timing motors, to thousands of kilowatts

for large industrial motors driving loads such as compressors or pumps.

MOTOR TYPES. Commonly used synchronous motors include hysteresis, inductor, permanent magnet, reluctance, and direct-current-excited types. All but the last type are generally in the small-horsepower category, with the hysteresis ad inductor types having subfractional-horse power ratings. Permanent magnet and reluctance types extend into the integral-horsepower range. Direct-current-excited machines can range from small integral-horsepower sizes to 25, 000hp or more. Following a brief review of each of the four smaller types, the remainder of this chapter dwells on the d-c excited machines – particularly the salient pole type.

Subfractional-horse power hysteresis motors have a smooth, cylindrical, cast magnetic-alloy rotor, which starts by virtue of hysteresis losses induced in it by the rotating field of the stator. The rotor locks into step due to the retentivity of the rotor material. These motors are used for timing and as drives for recording instrument where precise, constant speed is required.

Inductor motors have a slotted or toothed rotor. The stationary member

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13.03.18= 4 сем. 2018 ( Э -325 СН ) З / О АВИЭТ ВАРИАНТ 2

is equipped with a main winding and either permanent magnets or an

exciting winding to establish magnetic poles. Forces between the stationary poles and the rotor teeth produce torque. These motors are used on timer applications where load inertia is low.

Permanent-magnet motors have permanent magnets embedded in a squirrel –cage type rotor to produce fixed poles which lock into step with the armature field. Because of its relatively high efficiency and power factor, this motor is becoming increasingly popular in the fractional and lower integral- horsepower range.

Reluctance motors are the most common of the non-excited synchronous types, found in sizes from sub-fractional values up to about 100 hp. The rotor has salient poles (without permanent magnets or exciting windings) which lock into step with the rotating field due to reluctance torque. Some reluctance motors have smooth, cylindrical rotors with cast aluminium filling the space between the magnetic salient poles and also forming the rotor-cage winding for starting.Efficiency and power factor are lower than for wound, salient- pole, direct-current-excited synchronous motors. However initial cost is also lower.

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