II. Test yourself how well you have understood "the senses" of the texts dealing with transformers.

1. A transformer is a device which converts:

   1. mechanical energy into electrical energy;

   2. alternating current into direct current;

   3. the alternating current of one voltage into the alternating current of another voltage but of the same frequency.

2. The operating principle of transformers is based upon the phe­nomenon of:

   1. self-induction;

   2. mutual induction;

   3. electric induction.

3. The ends of the three-phase transformer windings of upper voltage are marked by:

   1. the capitals A,B,C;

   2. the capitals X,Y,Z;

   3. the small letters a,b,c.

4. An autotransformer possesses:

   1. one winding which is primary and secondary at the same time;

   2. two windings;

   3. many windings.

5. The efficiency of an autotransformer in comparison with that of an ordinary transformer of the same power is:

   1. higher;

   2. lower;

   3. absolutely the same.

6. The rated secondary voltage of shipboard voltage measuring instru­ments is:

   1. 120 V;

   2. 147 V;

   3. 127 V.

7. The rated secondary current of shipboard current measuring tr formers is:

Н.Л.ТРУХАНОВА, Н.А.КРАВЧЕНКО 2

АНГЛИЙСКИЙ ЯЗЫК 2

TROUKHANOVA N.L., KRAVCHENKO N.A. 2

ENGLISH 2

OF MARINE ELECTRICAL AND POWER ENGINEERING 2

FOR SEAMEN 2

- 51

2. TROUBLESHOOTING OF D.C. MOTORS 74

1. contact welding;

2. arc-welding;

3. electron-beam welding.

III. Mind your Grammar:

I. Complete the sentences with the correct form of Present Simple Active. Choose from the verbs in the box. Use each verb once only

become show provide

supply have range

interact be cause

1. Figure 12 in the last column . . . that the shift is equal to 360

2. Current and voltage measuring transformers . . . operational safety of ammetres, voltmetres, wattmetres etc.

3. The winding insulation breakdown and the overheating of the с . . . possible.

4. The voltage in the secondary windings . . . between 30 70 V.

5. Welding transformers ... the arc across the reactor.

6. Autotransformers only . . . one winding.

7. The transformer primary and secondary windings . . . elec magnetically.

8. The penetration of high voltage in a low voltage network . injury of an attending personnel.

9. The welding transformers' external characteristic ... steeply drooping.

2. Make one sentence from two using an -ing clause.

1. A transformer is an electromagnetic device. It converts an alternat­ing current of one voltage into an alternating current of another volt­age.

2. The current produces the alternating magnetic flux Ф in the core. It passes through the primary winding.

3. We obtain the transformer ratio. We divide one equation by anoth­er.

4. The alternating magnetic flux Ф in the core induces the emf of self-induction. It cuts the turns of the primary winding.

5. We obtain the value of the primary voltage U_l in a measuring cir­cuit. We multiply U₂ of the secondary winding by the transformer ratio к.

6. An autotransformer is a device. It has one winding - the primary and the secondary at the same time.

7. The transformer magnetic flux and the emf of the secondary open winding go up to dangerous values. They cause the insulation break­down of the winding and the overheating of the core.