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.
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.