Английский язык для судовых электромехаников - [32]

2. The power cam controllers are widely used for controlling a-c motors of deck machinery.

3. Simple construction, reliable operation and small dimensions of this intricate switching device make it possible for electric drives which do not have to meet stringent requirements as to wear resistance.

4. Electric drives used for marine services are controlled by means of series power controllers which are available in two sizes.

5. The power cam controllers of the KB series have watertight construction as per class IP 56 and are designed for installation on weather decks.

6. The power cam controllers are designed for vertical mounting on weather decks or on the machinery. If no contactors are mounted in controllers the latter can be arranged in a horizontal position with the cover upward.

7. The use of the power cam controllers in the electric drives of the deck machinery is restricted to motor ratings of 20 to 25 kW. The factors which impose such restrictions are the operating frequency exceeding 300 operating cycles per hour and the requirements for remote or two-stationed control.

8. For anchor-handling, mooring and similar equipment with rating of up to 20 kW the power cam controllers are the preferred type of controllers.

9. The choice of the power cam controllers for cargo hoisting gear must take into account the required wear resistance of the controller.

10. For devices with a small number of startings and irregular operation controllers may be selected with regard to the starting and rated currents. For highly efficient gear with a number of startings per hour greater than 150 the value of the allowable starting and rated currents must be decreased to 1 or 2 times, so that the v'ear resistance should increase 2.5 or'4 times, respectively.

Hometask: Ex. 35, 36.

The fifth class period

Review of “Ship electrical equipment”. 10

Topical content: Technical documentation of electrical equipment. 8

37 20

Give the exact translation of the Certificate and dwell on it with your fellow-student.

Lloyd’s Register of Shipping Certificate for AC Generator or Motor

Cert. No. Lon. 71083 Works order No. 51433

Main order No. 22/462 21.1.84 Intended for Ship/Yard/Eng.

Type MC 634 В

Date 19.12.84 Port London Manufacturer: Newage Engineers, Limited, Stamford, Lines.

Purchaser: A/S Norsk Elektrisk and Brown Bovery, Oslo, Norway.

Dates of inspection:

First 20.10.84 Last 13.12.84 '

This is to Certify that the ³auxiliary propulsion AC generator/stator, particulars of which are given below, has been inspected by me at the Makers’ works. The construction, workmanship and materials are good, and the machine complies with the relevant of the Society’s Rules.

On completion the ³generator/motor was tested with satisfactory results.

Rating

kVA 560 Volts 380/220 Phase 3

kW 448 Amps 850 Cycles 50

HP — Power factor 0.8 R.P.M. 1,500

Type of enclosure S.P. and D.P. Class of insulation Stator В

Machine No. 51433/1 Date of Rotor F

Temperature test Machine

13.12.84 acting as Generator

Results of Tests
				Generator
Duration	4 Hours	Degrees C.		Voltage regulation
R.P.M.	1,500			Auto or inherent
Volts	380	Cooling air 19
Amps	850	Stator winding 75.6		Full load	No load
Power factor 0.8		Rotor winding 89.7	R.P.M.	1,500	1,560
		Slip rings —	Volts	380	382
	Volts —
Field —	Amps —		Amps	880	—
Cycles	50

Overload test

1 min. 2kV 50% for 15 sc

Shaft. BIR 761055

(signature) Surveyor to Lloyd’s Register of Shipping.

Hot insulation High voltage test resistance (megohms) 100 volts AC for Identification marks No. 51433/1 Lloyd's Test Lon (port)

RAL/initials 13.12.84 (dale)

Fee 79.60 Expenses 1.70

Prior to the commencement of supervising the manufacture of the electrical equipment the following documentation is to be submitted for consideration: 1) description of the principle of operation and main characteristics; 2) material specification (list ol products) which is to contain elements, instruments and materials used and their technical characteristics; 3) assembly drawing with sections; 4) circuit diagram;

5) test programme; 6) mechanical rotor shaft calculations, as well as drawings of fastening of poles, magnetic circuit stackings, commutator, etc., and detailed drawings of elements welded to the shaft; 7) for distribution switchboards — calculation of thermal and electrodynamic strength of busbars under short-circuit conditions and choice of apparatus to fit these conditions where current rating of a generator or generators running in parallel exceeds 1,000 A.

The sixth class period

Listen carefully to the recorded (ext. What distinguishes these two texts?

Resistors

A

A resistor is one of the most common elements of any circuit. Resistors are used: 1) to reduce the value of current in the circuit, 2) to produce 1R voltage drop and in this way to change the value of the voltage.

When current is passing through a resistor its temperature rises high. The higher the value of current the higher is the temperature of a resistor. Each resistor has a maximum temperature to which it may be heated without a trouble. If the temperature rises higher the resistor gets open and opens the circuit.