Английский язык для моряков / Англ Труханова

7.Is there any difference between capital repair of а d.c. machine and that of an а.с. machine?

8.Is the brushgear of an а.с. machine laid under repair?

4. CAPITAL REPAIR OF D.C. AND А.С. MACHINES

Capital repair of electric machines is basically caпied out in elec­ trical workshops of ship-repairing factories.

Capital repair of а d.c. machine is predominantly performed with the following procedures:

1.DisassemЫing а machine with removing its armature, poles with coils, bearings;

2.Complete or partial rewinding of windings with replacing wedges and slot insulation;

3.Impregnating а winding with varnish, drying, enamelling and re­ drying it;

4.DisassemЫing and removing the commutator with replacing mi­ canite gaskets between commutator plates and cone micanite insu­ lation;

5. AssemЫing а commutator on а shaft Ьу а pressed fit, tuming it on

а lathe, slotting, grinding and polishing it;

6.Replacing armature bandages and performing static balance;

7.Rewinding а half of both the main and commutating poles, repair­ ing the others, drying, impregnating them with varnish, drying them and enamelling pole coils;

8.Mechanical repair of а brush-rocker and brush-holders as well as restoring galvanic coating on the parts;

9.AssemЫing а machine, grinding its brushes on а commutator, check­ ing gaps;

10.Adjusting, testing а machine on а test-bed, mounting it on its bearer and testing for operation.

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Capital repair of an а.с. machine includes partial or complete rewinding of both the stator and the rotor. Damages in а cage motor - those of its legs and end rings - are corrected as well. Generator exciters are also placed under repair and the latter is cairied out in much the same way as that of а d.c. machine.

VOCABULARY

QUESTTONS

l.Where is capital repair of electric machines basically carried out?

2.What are the procedures of capital repair of windings?

3.what are the procedures of capital repair of а commutator?

4.What are other procedures?

5.What is the principal difference between capital repair of а d.c. ma­ chine and that of an а.с. machine?

6.What damages in а cage motor are corrected?

7.How are generator exciters in an а.с. machine repaired?

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EXERCISES

1. Think о/English equivalentsfor suggestedRussian words and word comblnations and complete the sentences:

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13. The lists of materials, ___________ (запасные и

IL Choose опе о/the /inking words or word comЬinationsfrom 'е Ьох and complete the sentences.

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1. Magnetism is the property of the molecules of iron and other cer-

3. The resistance of metals increases with the increase in the temper-

5.Their windings ___ those of the main poles are built of сорper conductors.

6.As this takes р\асе, the machine operates __ а generator.

7.Shunt, series and compound generators are self-excited;

______ they don't require а separate current source for their excitation.

8.in the figure, curve 3 passes above no-Ioad curve.

9. They aren't remagnetized rection in the field winding.

10. overcome this force, the external force should Ье exerted upon the generator circuit.

11.Such а current is dangerous for the armature winding and а machine

12.It is attained Ьу changing the field current ____ an adjusting rheostat placed in series with the arrnature circuit.

13.The speed of rotation is altered moderately -.. predominantly

______ the voltage drop in the armature.

14. The starting torque of the motor is rather small, directly proportional to the arrnature current; the current consumed from the mains is proportional to the \oad on the shaft.

15._____ its capacity, а rotary amplifier may operate as either an exciter or а generator.

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UNIT 9.

ELECTRICAL SAFEТY

1. ТНЕ MAIN REASONS OF ELECTRICAL TRAUMATISM AND

MEANS OF PROTECTION AGAINST IT

The main reasons of e\ectrical traumatism on board ships are the following:

•rough infringement of Rules of both shipboard electrical maintenance and electrical safety;

•live-line maintenance without observing protective measures;

•imperfection of operation manual of electrical mechanisms (those of deck machinery, engine-room etc.);

• imperfection of construction of wiring accessory;

•faultiness and imperfection of portaЫe accessory and portaЫe tools;

•lack of uniformity in the choice of voltages of start regulating equipment control circuits;

•unsatisfactory condition of the mains electrical insulation;

•ill-timed elimination of the trouЫes and damages of the electrical equipment occurred;

•formal instructing on safe methods of work.

The use of e\ectrical energy on board ships is not only associated with the danger of electric shock hazard of an operating personnel but also with possiЬ\e fires.

Under norrnal conditions а therrnal effect ofan electric current is rated, i.e. the heating of conductors and current-Ieading parts ofthe elec­ trica\ equipment is calculated so that it not exceed fixed rates.

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If the Rules of shipboard electrical maintenance and safety are not observed, ifdamages ocёutarid the environmental.conditions (dampness, dust, chemically active substances) affect the electrical equipment, its normal state is broken. Оп electrical sets there emerge short-circuits, overloads, large transient resistances, arc and spark discharges, which сап also cause fires.

То protect an operating personnel ofelectrical sets against electric­ shock hazard there exist principal and additional protective means.

Principal protective means are those the insulation of which is reliaЫe enough to withstand а working voltage of an electrical set and makes it possiЫe to touch hot-line cuпent-leading parts. Оп electrical sets with voltage up to 1,000 V the above mentioned means are the fol­ lowing: insulating gloves, tools equipped with insulated handles, volt­ age indicators, insulating and clip-on instruments.

Additional protective means are not designed to ensure protec­ tion against electric shock hazard, but against а расе voltage and detri­ mental effect of an electric arc and the products of its burning. Such means are the following: insulating galoshes and high overshoes, insu­ lating rubber rugs, insulating stands.

There are also auxiliary protective means designed for individu­ al protection of an operating personnel against light, thermal and me­ chanical effects. They are protective glasses, gas-masks, special gaunt­ lets etc.

VOCABULARY

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QUESТIONS

1.Is the thermal effect of an electric current rated under normal con­ ditions?

2.ln what way is the heating of conductors and current-leading parts calculated?

3.What happens if the rules of shipboard electrical maintenance and safety are not observed?

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4.What are the phenomena emerging on electrical sets that сап cause fires?

5.What are the principal means protecting an operating personnel against electric shock hazard?

6.What are the additional means protecting an operating personnel against а расе voltage and detrimental effect of an electric arc?

7.What do you call the means designed for individual protection?

8.What are the auxiliary protective means?

2. SOME RULES FOR SAFE PRACTICE AND AVOIDING

ELECTRIC SHOCKS

Electricity сап Ье dangerous and even fatal for those who do not understand the simple rules of safety. There are many fatal accidents involving Ьу а well-trained personnel who violates the basic rules ofper­ sonal safety.

Currents above 100 milliamperes or only one tenth ofan ampere are fatal. А workman who has contacted currents above 200 milliam­ peres may live to see another day ifgiven rapid treatment. Currents be­ low 100 milliamperes can Ье serious and painful. А safe rule:

р/асе yourselfin аposition to get апу kind ofа shock.

Неге are some rules that should Ье observed to avoid electric shocks.

1. Ве sure ofthe conditions ofthe equipment and the dangers present before working on а piece ofequipment. Many sportsmen are killed Ьу supposedly unloaded guns; many technicians are killed Ьу supposed "dead" circuits.

2. Never rely on safety devices such as fuses, relays and interlock systems to protect you. They may not Ье working and may fail to pro­ tect when most needed.

3. Never remove the grounding prong of а three wire input plug. This eliminates the grounding feature ofthe equipment making it а po­ tential shock hazard.

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4.Do not work оп а cluttered bench. А disorganized mess ofcon­ necting leads, components and tools only leads to careless thinking, short­ circuits, shocks and accidents. Develop hablts of systemized and orga­ nized procedures ofwork.

5.Do not work оп wetfloors. Your contact resistance to ground is

substantially reduced. Work оп а rubber mat or an insulated floor.

6.Do not work а/опе. lt'sjust good sense to have someone around to shut offthe power, to give artificial respiration and to call а doctor.

7.Work with опе hand behind уои or оп your pocket. А current between two members crosses your heart and сап Ье lethal. А wise tech­ nician always works with one hand.

8.Never talk to апуопе while working. Don't let yourself Ье dis­ tracted. Also, don't you talk to anyone, if he is working оп dangerous equipment. Don't Ье the cause ofan accident.

9.Always move slowly when working around electrical circuits. Vi­ olent and rapid movements lead to accidental shocks and short circuits.

1.In what case сап electricity Ье dangerous and fatal?

2.What currents are fatal?

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