Т.Ю.Кущ, М.С.ВоловникАнглийский язык для судовых электромехаников. ENGLISH FOR MARINE ELECTRICAL ENGINEERS. 1986

case.

1. This device is out of use nowadays. 2. Why don’t you have the use of the motor? 3. This conference is of great use for all of us. 4. I’m afraid I’m of no use here. 5. There’s no use to employ this wattmeter. It seems to be out of order.

Translate at sight the sentences with Gerund.

1. Reading scientific books is useful. 2. We object to the authors of this paper not referring to our paper. 3. I hate missing'lectures. 4. They started working. 5. He stopped removing bearings. 6. For the sake of avoiding the introduction of further terminology...

17 2

Find Gerund in the following sentences. Read and translate them.

1. This rule applies above all for rising temperatures. 2. Transformers are used for raising or lowering voltages and, aside from this in some cases, for measuring purposes. 3. You must have patience for learning foreign languages requires time.

18 9

Translate as exactly as you can. Look up new words in a dictionary. Render the text in English.

A bridge is a sensitive device used to measure resistance, capacitance, or inductance when great accuracy of measurement is desired. Bridges are commonly used for measuring the reactance of components and for accurately determining audio frequencies. Bridge circuits for component measurement include a source of a-c or d-c voltage; an indicating device, usually a sensitive galvanometer or headphones; an adjustable standard, usually a resistor or capacitor; the component whose value is to be measured; and a method of determining how much the unknown value differs from the standard.

19 8

Express the main idea of the whole text in Russian. Make up a plan of the text. Dwell on its subject with your fellow-student.

Measuring Instruments and Alarms

Given below is a minimum list of measuring instruments that are to be provided in order to ensure permanent and direct indication of the system parameters: 1) an ammeter in the main current circuit;

2) a voltmeter in the main current circuit; 3) an ammeter in the field circuit for adjustable excitation system; 4) a voltmeter in the field circuit for adjustable excitation system; 5) a tachometer for propulsion motors or propeller shafts; 6) a rudder angle indicator.

For a-c systems the following is to be provided additionally: 7) a frequency indicator; 8) a synchronizer for generator paralleling.

The electric propulsion plant system is to be equipped with an insulation resistance measuring instrument. Continuous insulation resistance measuring is to be provided in the main current circuits, with visual and audible alarms to operate in the event of inadmissible decrease of the insulation resistance.

Where a control desk or a control panel incorporates measuring instruments with oil, steam or water supply to them, suitable measures are to be taken to prevent the possibility of any of the above agents gaining access to live parts if the instruments or piping connections are damaged.

20 9

Answer the questions related to the text below.

1. What do they call truly ammeters?

2. What sort of measuring instrument is called a voltmeter?

3. What is the construction of most meters?

4. Which is more common: the electrodynamometer types of instrument

or the permanent magnet (PM) type?

5. Under what condition does the instrument become a wattmeter?

6. How do dynamometers differ from PM instruments?

Fundamentally, all meters measure current and in this sense are ammeters. When they have low internal resistance so as to produce no effect on a circuit’s performance and are actuated through direct connection in series with the main current path, they are truly ammeters. When they have high resistance so that they may be placed in shunt or directly across a voltage source they are called voltmeters. Their indication of voltage is based on the product of a known, calibrated internal resistance in series with the meter movement, and the current flowing through that resistance.

Most meters are constructed to use the attractive and repulsive force characteristics of magnetic structures to produce deflection of a pointer. In the most common PM type mutual force is exerted upon a movable, pivoted coil which itself becomes a magnet when it passes d-c current being measured.- When a movable magnet is mounted in the

field of a fixed permanent magnet and when it is passing current of the correct polarity, a force is exerted upon the movable magnet. In the resultant alignment of the fields, definite and proportional movement is produced against the restraining force of a spring connected to the pivoted coil. Deflection is arranged to be proportional to the amount of current through the coil, so that <5 hwhen the meter scale over

which the pointer moves Fig. 1. Basic d-c meter movement using pivoted coil is calibrated, a true indi-and permanent magnet cation of current is ob

tained.

The basic d-c meter movement uses the pivoted coil and a PM. (Fig. 1). The electrodynamometer type of instrument, which is less common than the PM type, employs the same basic moving-coil mechanism but uses a fixed electromagnetic field actuated by current xvhich is related to or proportional to that in the moving coil.

When the current through a circuit is sent through the fixed-mag-net coil and the voltage across it applied to the movable coil, this instrument becomes a wattmeter, since deflection is then proportional to the product of voltage and current.

Dynamometers are less flexible than the PM type meters, less sensitive, and generally more expensive. Their basic arrangement, however, allows them to be used on either a-c or d-c when appropriate scale multiplier, and shunt arrangements are included in their internal circuitry.

21 15

Home exercise. Having read the text below complete the following sentences in such a way that they make sense. .

1. In the moving iron-vane type, induced currents*are used to produce magnetic force on a structure bearing a pivoted pointer and a vane which is ... a) heat-generating input current; b) input voltage-charged condenser plate; c) thin iron element.

2. Rectifier elements mounted within the meter case may be. . . a) copper oxide, selenium, germanium, or silicon; b) dry wood, bakelite, mica;

c) alkaline nickel-cadmium cells.

3. Moving iron-vane meters usually have relatively low impedances and are. . . a) complex and cheap; b) designed for operation over as wide a band of frequency as possible; c) simple and inexpensive.

4. The use of moving iron-vane meters must be restricted to the .... a) voltage for which they are designed; b) frequency for which they are designed; c) current for which they are designed.

A-C Indicating Meters

The moving iron-vane type is the most common a-c meter. In ii induced eddy currents are used to produce magnetic force on a structure bearing a pivoted pointer and a thin iron element called a vane. The vane has no coil. The stationary magnetic field is* produced by a single current-carrying coil surrounding both the fixed metal element and the pointer movement. This coil is so arranged that its own field induces a field in the moving vane and in addition generates attractive or repulsive magnetic forces with respect to its own self-produced magnetic field. Deflection is basically proportional to the current through the main coil.

Moving iron-vane meters usually have relatively low impedance and are simple and inexpensive. They measure either voltage or current, but their use must be restricted to the frequency for which they are designed.

Rectifier type meters utilize PM d-c movements actuated by current developed from rectifying the applied a-c being measured. Rectifier elements mounted within the meter case may be copper oxide, selenium, germanium, or silicon. The developed d-c is proportional to the applied a-c while the rectifiers and associated circuitry are designed for operation over as wide a band of frequency as possible.