Методическое пособие для студентов iv курса очного и заочного обучения специальности 26. 05. 07 "Эксплуатация судового электрооборудования и средств автоматики"
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UNIT VIII. ELECTRIC SPECIAL PURPOSE MACHINES1. Read and remember the following words and word combinations.
2. Read and translate the text. ELECTRIC SPECIAL PURPOSE MACHINES On board ships separate electrical energy consumers (radiocommunication, electric radionavigational instruments etc.) require special sources of energy, the main electrical properties of which (voltage, the kind of current, frequency) are different from those of shipboard electric power station. For the purposes of converting electrical parameters of shipboard electric power station into required ones such machines as converters are used. Rotary converters may be either multiarmatured or one-armatured. The general disadvantage of all rotary converters is both the moving contact in the commutator-brushgear transition and the rotating parts, which makes the converters considerably less reliable and harder to operate. At present time static converters are widespread on board ships. They are deprived of the drawbacks indicated above. Another variety of an electric special purpose machine is amplifiers. They are distinguished as magnetic amplifiers and rotary amplifiers. Magnetic amplifiers (MA) have acquired a wide application on board ships being designed for automatic regulation, monitoring and control of various marine sets. They are advantageous in not having moving parts, being simple in construction and easy in operation, possessing high reliability and efficiency, being characterised by instant readiness and resistance to moisture and vibration. Magnetic amplifiers are provided to control a big power by expending a small one. Rotary amplifiers (RA) find application in automatic control and regulating circuits of marine generators and servomotors included into the adjustable-potential systems. Depending on its capacity a rotary amplifier may operate as either an exciter or a generator of the system. The most widespread type of a rotary amplifier is an amplidyne owing a cross field. It is a d.c. generator specially constructed with a number of advantageous features: a big magnification ratio, small inertia capability, a big overload capacity etc. Another electric special purpose machine is a tachogenerator. It is designed for converting the speed of rotation of the shaft possessed by machines and mechanisms into the proportional electric voltage. A tachogenerator is required to keep linearity and symmetry of an output characteristic within the entire range of the change of either the speed of rotation or the direction of rotation. On board ships d.c. and a.c. tachogenerators are used to measure the speed of rotation of propulsion shafts and other mechanisms. They are also provided in automatic systems to obtain the rotational speed feedback. Synchronous transmission systems are called selsyn systems. Various instruments designed for controlling the operation of the ship base themselves on selsyns. Such instruments as engine and bridge telegraphs, a gyro-pilot, a gyro-compass, tachometres of propulsion shafts, logs etc. are installed to ensure the control of steering gear positions, the operation of the boilers, the ship's speed and the direction of the ship's motion. A selsyn is composed of both the stator and the rotor. In construction, selsyns are divided into those provided with slip-rings and those deprived of them. Slip-ringed selsyns, in their turn, may be equipped with either the primary one-phase field winding mounted on the stator and having salient poles or the secondary three-phase synchronisation winding mounted on the rotor and having non-salient poles. 3. Match the following English and Russian word combinations. a) on board ship, for the purpose of, overload capacity, instant readiness, to acquire a wide application, deprived of drawbacks b) мгновенная готовность, перегрузочная способность , лишенный недостатков, получить широкое применение, в целях, на борту судна 4. Answer the questions. 1. For what purposes are converters used? 2. What types of converters do you know? 3. Which type of converter is advantageous on board ships? Why? 4. What types of amplifier do you know? 5. Why has a magnetic amplifier acquired a wide application on board ships? 6. What is a magnetic amplifier designed for? 7. Where does a rotary amplifier find application? 8. What may a rotary amplifier operate as depending on its capacity? 9. Which type of rotary amplifier is the most widespread on board ships? Why? 10. What is a tachogenerator designed for? 11. What are D.C. tachogenerators and a.c. tachogenerators used for on board ships? 12. What types of synchronous transmission system do you know? 13. What instruments base themselves on a selsyn? What are they responsible for? 14. What parts is a selsyn composed of? 15. What types of selsyn do you know? 5. Complete the following sentences with the correct -ing and - ed forms. Select the right verb from the box using it once only:
1.The stator is found in the frame with the core . . . inside and … of 0,35-0,5mm electrical steel laminations. 2. A lot of shipboard alternators operate at the speed of rotation . . from 500 to 1500rev/min. 3. Magnetic amplifiers are electric special-purpose machines . . by instant readiness and resistance to moisture and vibration. 4. An amplidyne is a D.C. generator specially . . . with a number advantageous features. 5.The most widespread type of rotary amplifier is an amplidyne . . a cross field. 6. Slip-ringed selsyns may have either the primary one-phase field winding . . . salient poles or the secondary three-phase synchronization winding . . . non-salient poles. 7. Three-phase cage motors are induction motors . . . ship's auxiliaries, anchor-mooring mechanisms, cranes, winches. 8. The core and aluminium legs . . . from their ends can be found in the core slots. 9. The cores of the poles have the field windings . . . their supply through slip-rings and brushes. 10. A great deal of ship alternators have the rotor . . . with salient poles. 6. Fill the gaps after the modal verbs with the Passive Infinitive. 1. The copper and aluminium legs can . . . (find) in the core slots. 2. The way in which the rotating field is established in the stator m . . . (describe) as follows. 3. The current value can . . . (adjust) by varying the air-gap of reactor magnetic conductor. 4. Measuring instruments should . . . (rate) in accordance with the voltage indicated above. 5. Slip-ringed selsyns can . . . (provide) with the primary on phase field winding. 6. Insulation stands must . . . (use) to protect personnel against a phase voltage. 7. Insulation gloves should . . . (put) on when it is necessary to withstand a working voltage of an electrical set. 8. If the rules of the electrical maintenance and safety are not observed, the normal state of the equipment may . . . (break). 9. The troubles must . . . (eliminate) in time. 10. The test procedure of this autotransformer should . . . (do) in accordance with the safety rules. 7. Speak about electrical special purpose machines. |