Заняття 51
Тема: Апаратура керування та захисту електроприводів: перемикачі універсальні, шляхові вимикачі
Граматичний матеріал: Питання до різних членів речення
Вправа 1. Прочитайте та перекладіть лексику за допомогою словника.
сontactless traveling switches [ˈtrævlɪŋ ˈswɪʧɪz ]
in schemes [ɪn skiːmz ]
electromagnetic relay [ ɪˌlɛktrəʊmægˈnɛtɪk riːˈleɪz ]
operating element [ ˈɒpəreɪtɪŋ ˈɛlɪmənt ]
class of accuracy [ klɑːs ɒv ˈækjʊrəsi ]
extent of protection [ɪksˈtɛnt ɒv prəˈtɛkʃən ]
primary drive [ ˈpraɪməri draɪv ]
sensitive element [ˈsɛnsɪtɪv ˈɛlɪmənt ]
mutual inductance [ˈmjuːtjʊəl ɪnˈdʌktəns ]
converters [ kənˈvɜːtəz ]
magnet inductive switches [ ˈmægnɪt ɪnˈdʌktɪv ˈswɪʧɪz ]
capacitor switches [kəˈpæsɪtə ˈswɪʧɪz ]
gap [gæp ]
permeability of a gap [ˌpɜːmjəˈbɪlɪti ɒv ə gæp ]
beam switches [ biːm ˈswɪʧɪz ]
slot-hole [slɒt-həʊl ]
plane [ pleɪn ]
face[ feɪs ]
on an accuracy class [ɒn ən ˈækjʊrəsi klɑːs ]
adjusting dimensions [ əˈʤʌstɪŋ dɪˈmɛnʃənz ]
precision [ prɪˈsɪʒən ]
transistor amplifiers[ trænˈzɪstər ˈæmplɪfaɪəz]
Вправа 2. Прочитайте та перекладіть текст українською.
Contactless Traveling Switches
Contactless traveling switches (the converters of a way working without mechanical influence from a moving emphasis) are used in schemes of control of electric drives of machines, mechanisms and cars. Contactless switches are intended for switching of chains of management by means of electromagnetic relays or contactless logical elements which is carried out under the influence of the operating element.
Classification of contactless traveling switches
Contactless traveling switches can be classified on: 1- to a way of impact on a sensitive element, 2- physical principle of operation of the converter, 3 - design,
4 - class of accuracy, 5 - extent of protection.
O
n
a way of impact on a sensitive element contactless traveling switches
can be divided into switches of mechanical and parametrical action.
In switches of the first form the operating element influences directly mechanically to the primary drive of the contactless traveling switch which interacts with a sensitive element without contacts. In switches of the second form depending on the position of the operating element which is mechanically not connected with the contactless traveling switch any physical parameter of the converter changes. At a certain value of this parameter the condition of a relay element changes.
Classification of contactless traveling switches by the physical principle of operation of the converter includes the following types:
The inductive switches constructed on change of induction, mutual inductance, and also induction switches.
Now the majority in lots of the contactless traveling switches which are producing the industry are inductive devices. In turn converters of inductive contactless traveling switches can be constructed according to the following schemes: resonant, auto generator, differential, bridge, direct transformation.
Magnet inductive switches which are constructed on the following principles: effect of the Hall, magnet resistor, magnet diode, magnet thyristor.
Capacitor switches: with the changing area of plates, with the changing gap between plates, with the changing dielectric permeability of a gap between plates.
Photoelectronic switches with elements: photodiode, phototransistor, photoresistor, photothyristor.
Photo-electric switches and adjoining to them beam switches in which along with rays of visible light beams of other physical nature can be used beams, for example radioactive radiation.
According to the design contactless traveling switches are subdivided on:1- slot-hole, 2-ring (semi-ring), 3-plane, 4-face, 5-switches with the mechanical drive, 6- multi element switches.
On an accuracy class (size of the main error) contactless traveling switches share on switches low (about ±0,5 mm and more), average [about ± (0,05 - 0,5) mm], raised [about ± (0,005 - 0,05) mm] and high (about ±0,005 mm and less) accuracy.
Contactless traveling switches can possess various extent of protection against hit of foreign solid bodies and penetration of water in the device.
Technical characteristics of contactless traveling switches:
1
-Precision
(metrological) characteristics, 2- speed, 3- electric
characteristics,4- the overall and adjusting dimensions and weight,
5- nominal and admissible working conditions, 6- reliability
indicators, 7- cost and so on.
One of the main characteristics of contactless traveling switches which is directly influencing its design and some other technical characteristics is defined by a geometrical arrangement of the operating element of rather sensitive surface in operating time. For plane contactless traveling switches as the main characteristic the working gap is the distance between a sensitive surface of the switch and the operating element at which there is an operation of the switch is accepted. The main characteristic of the face switch is the maximum distance of influence, i.e. the maximum distance between a sensitive surface of the switch and the operating element at which change of its switching state is possible. The main characteristic of a slot ring switches is width of a crack and internal diameter of a ring of these switches respectively.
Speed (reaction time) of the contactless traveling switch this is time between the moment of establishment of coordinate of operation and the moment of achievement of the established value of tension at the exit of the contactless traveling switch. Knowing the size of speed of the contactless traveling switch, it is possible to define dynamic errors of operation of contactless traveling switches at changing of speed of the managing director of an element.
Electric characteristics of contactless traveling switches include the demanded parameters of the power supply (power line) and load characteristics.
It is necessary to carry also overall and adjusting dimensions of contactless traveling switches to the major parameters.
C
ontactless
switches of the slot-hole BVK-24 type
Contactless switches of slot-hole type with the transistor amplifiers working in the generating mode were widely adopted. In fig. 1, and the general view of the BVK-24 switch is shown. Its magnetic conductor placed in the case 4 consists of two ferrite cores 1 and 2 with an air gap 5-6 mm wide between them. In the core 1 primary winding of wk and a winding of positive feedback , in the core 2 – a winding of negative feedback is placed. Such magnetic conductor excludes influence of external magnetic fields. Coils of feedback are switched on consistently – opposite. As the switching element the aluminum petal (plate) 3 up to 3 mm thick which can move to cracks (in an air gap) magnetic system of the sensor is used.
Contactless traveling BVK-24 switch: 1- general view; 2 - basic electric circuit
1 2
Scheme of turning on of the BVK contactless switch
Scheme of consecutive turning on of two BVK contactless switches
Scheme of parallel turning on of two BVK contactless switches
KVD contactless switches
Contactless KVD limit switches are intended for switching of electric chains of management and the alarm system at automation of various systems. The electric schematic diagram includes the generator and the trigger on transistors. At introduction to a working gap of a metal plate there is a reduction of coefficient of feedback causing generation failure, the trigger overturns, and normally closed output transistor opens that causes operation of the relay or a logical element. Supply voltage - 12 or 24 V.
Вправа 3. Дайте відповіді на питання.
Where are contactless traveling switches used?
For what contactless switches are intended?
How can be classified contactless traveling switches?
What are the differences between mechanical and parametrical switches?
What do you know about the inductive switches?
What are the other types of contactless switches on operating in physical principle?
How are contactless traveling switches subdivided on according to the design?
What are the technical characteristics of contactless switches?
How do contactless switches of slot-hole type work?
For what are contactless KVD limit switches intended?
Вправа 4. Знайдіть еквіваленти з колонки А до слів з колонки В.
-
A
B
mechanical influence
ланцюги управління
moving emphasis
механічний вплив
chains of management
рухомий упор
оn a way of impact
під час роботи
change of induction
габаритні
the majority
напівкільцеві
semi-ring
багатоелементні вимикачі
multi element switches
зміна індуктивності
overall
за способом дії
in operating time
більшість
Вправа 5. Доповніть речення.
The electric schematic diagram includes the generator and … … … .
Contactless switches of slot-hole type with the transistor amplifiers working in the generating mode … … … .
Electric characteristics of contactless traveling switches include the demanded parameters … … … .
It is necessary to carry also overall and adjusting dimensions of contactless traveling switches … … … .
For plane contactless traveling switches as the main characteristic the working gap is the distance between a sensitive surface of the switch and the operating element at which there is … … … .
Граматичний матеріал: Питання до різних членів речення. Спеціальні питання
Питання до окремих членів речення називаються спеціальними.
Питання до окремих членів речення називаються спеціальними. Вони починаються словами who, what, where, why, how тощо. Питання можуть ставитися до різних членів речення.