Английский язык для судовых электромехаников - [44]

Fig 7. Converlor module

equipment. The convertor control equipment, in other words the electronic control circuits, consists of circuit boards mounted on a hinged panel. On convertor module 40—400 A the panel is supplied fixed in position; for the 650—1400 A module it is supplied separately.

The convertor control equipment is located on the inside of the panel. The permanent basic functions are grouped on one circuit board, known as the mother board. A number of optional functions in the form of small circuit boards can be connected to this mother board.

36 20

Home exercise. Write the exact translation of the second part of the text above. Be prepared to dwell on convertor module using Pig. 7.

Part II

Mounted on the outside of the. hinged panel is drive control cquip-

merit. The sub-functions are in the form of circuit boards connected to a mother board which provides all the internal connections between the sub-functions. Drive control equipment communicates with the convertor control equipment via a flat cable.

A convertor module can be fitted with all the options available for the convertor control equipment and the drive control equipment.

N. B. The open-core transformer for earth fault protection is supplied as a separate unit.

For supply voltages up to and including 500 V, the primary voltage of the auxiliary supply transformer is the same as the supply voltage of the convertor module. Where the supply voltage is higher, the transformer must be supplied separately with 500 V 60 Hz or 460 V 60 Hz.

For rated currents 230 A and above, an external supply at ПО V 50 Hz or 115 V 60 Hz is required to power and operate a cooling fan.

37 50

Home exercise. Read the text and then write a summary in English. Speak on some of the details of an electronic system operation that you know and that are provided bv the text. Use Fig. 8.

Fig. 8. Simplified block diagram

Electronic System. Operation

Programmable signal processing with the electronic system means that the executive functions of a process control system, e. g., is initiated and controlled by a program stored in a memory. On the basis of measured data collected from the process, the system performs the action laid down in the program. The function is therefore not tied to the electrical wiring of the system; it can be adapted to changed operating conditions simply by changing the program.

All function units are connected to the bus and operate jointly with the controlling unit. The control unit may contain a microprocessor and may be mounted on a circuit board of the same type as the other units in the system. It can also consist of a mini-computer, in which case the system acts as an interface with the process.

The objects in the process determine the nature and number of input and output functions, regardless of the operation of the system. The Fig. 8 shoxvs schematically a system in which four of the function units (circuit boards) are used for connection to the process. They include analog and digital input units for transducers and position contacts, and analog and digital output units for control signals to regulators, relays and indicating devices.

The flow' chart for the process shows how the executive components are to operate and perform the process. It serves as a basis for a program list, from which the program is transferred via a magnetic tape to programmable read-only memories. The memory circuit board and a microprocessor circuit board together constitute the controlling unit, which

controls the operation of the system. The control unit reads ‘the input signals and supplies control signals for the executive components in the process on the basis of this.

The program sequence, the supply voltage and certain sections of the bus are checked in a supervising unit which operates an alarm if an error is detected, and makes the output function's safe in order to prevent the process assuming a dangerous state.

Hornet ask-. Ex. 36, 37.

10

The fifth class period

Review of “Power plant control system” and Participle constructions.

38 10

Write a one-page precis about design and operation of power plant control system.

39 11

Dwell on the design and operation of power plant control system with your fellow-student. Use Fig. 8.

10

40

Write the exact translation of the text and then ask each other questions covering this text.

DC Voltage Transducer

This delivers an output voltage proportional to the armature voltage or induced voltage. The output signal is mathematically isolated from the input voltage. The armature current signal is used to compensate the output signal for armature current variations in such a way that the output signal is approximately proportional to the induced EMF.

Where accurate EMF measurement is required, the measuring circuit also has an input which may be connected to the terminal of the machine. The voltage drop across the commutation winding of the machine is then used for IR compensation, and this arrangement therefore compensates to a considerable degree for the dependence of winding resistance on temperature.