Английский язык для судовых электромехаников - [55]

On the bridge, both audible and visual alarms are to operate and indication given when the speed of the main engines is to be reduced due to the following fault condition: high scavenge air temperature, oil mist detected in crankcase, low piston coolant outlet flow, low piston coolant pressure, also for low cylinder coolant pressure if on a separate circuit.

Where the lube oil cooling water and oil fuel booster pumps are not driven by the main engine, the standby pump is to start automatically if the discharge pressure from the working pump falls below a predetermined value.

Iiomeiask: Ex. 32. 33.

The fifth class period

Read the text, mind logical units. Translate the text at sight.

Thyristor Convertors

The convertors in dc drive systems are designed to control and supply separately-excited dc machines in aimlications that demand rapid response. high accuracy and great reliability.

"The convertors are available with single-convertor arrangement and in double-convertor arrangement.

Operation. The armature simply unit has a closed-loop current control system which ensures that the armature current follows the set current reference. The svstem is based on a current controller, the output signal of which can influence the armature current via the control pulse circuits and the thyristor unit. The current measuring circuits continuallv supplv the current controller with information on the actual value of the armature current, and when this is compared with the reference an error signal is obtained which corrects the output voltage of the controller if necessary.

The controller current includes circuits for adaptive control. This means that the gain of the controller increases if the current is discontinuous. This maintains the response time of the current control system. A tynical response time for the current control is 10—15 min.

The current control system includes a buffer amplifier for the actual current value. This makes it possible to connect a meter to display the armature current, for example. By applying a control signal, the output of the buffer amplifier can be converted, so that the output signal changes sign when the direction of current flow changes in a double convertor.

37 3

Choose a suitable title for the text. Give reasons for your choice.

Double convertors have blocking circuits which switch the control pulses to the correct thyristors to give the required direction of the current flow. The input signal for the blocking circuits is the total current reference.

When the direction of current flow changes, the output voltage of the convertor is automatically matched to the armature voltage of the dc machine, so that current begins to flow immediately. This arrangement saves the time that would otherwise be needed to drive the current controller to the control voltage that gives through the machine.

38 6

Dwell on thyristor convertors with your fellow-student. Use ex. 36, 37.

Home exercise. Read the words, explain the function of their suffixes and prefixes. Give Russian equivalents for them:

REmove, careFULLY, installaTION, exactLY, ventilatING, openING, deterioraHON, resistANCEs, housING, insulaTION, OVERload, excess-IVE, connecTION, PREmature, rotaTION, failURE, maintenANCE, RE-newING, Disassemble, REplace, useLESS, internAL, pressURE, abra-SION, withIN, withOUT, sufficiENT, inspecTION, DEfault, REset, UNDERcurrent, UNtapped, considerABLY. machinERY, equipMENT, relationSHIP, comprehensIVE, hardWARE, reliabillTY, surveillANCE, UNused, softWARE, REbuildING, invertER, triAL, personnEL, ANTI-vibration, OVERall, Alive, ENcourage, transmisSION, Alike, domestic, throughOUT, AFOREmentioned, MISused, COUNTER-voltage.

40 20

Home exercise. Read the text and write out the names of main parts of a vacuum cleaner. Describe the steps taken by the psychiatrist in his treatment. What is your opinion of labour-saving devices?

Labour-Saving Devices

Quite a crowd had gathered in front of the local hospital. Presently the white door opened and Doctor Curewell himself appeared there. His voice sounded loud and clear when he said addressing the crowd:

— He’s gone to nuts, thinks he’s a vacuum cleaner!

— Poor old James, — murmured many voices.

You see, James Parker had a small workshop and was said to be able to mend anything from a coffee mill to a TV set. Whenever anything went wrong it was James that people went. They found him always in his workshop with a drill or a hammer in his hand, always smiling and always ready to help.

With the passage of time there were more and more various labour-saving devices, and the difficulties seemed to have piled up but this did not seem to worry old James. . . They say he loved screwdrivers and nuts as though they were living things and there was not a happier man in the whole of Suffolk. And he grew more and more famous until that dreadful day when he got it into his head he was nothing but an electrical vacuum cleaner. . . Fancy such a man wanting to suck in the dirt and dust of his house and those of his neighbours, and what a blow it must have been to all his friends!