3. Simulation of AC static switch controllers

The simulation of static switch function is realized like a Windows independent application helping with Visual Basic's software package [1, 4, 5]:


Press the button for the continuation of simulation (Continua).

It opens the simulation window of the single-phase AC switch controller (Figure 10).

The simulation window containing three main parts [4]:


In the laboratory classes, students choose the type of the switch controller, making different simulations to understand the principle of operation in each case. During the simulation, besides information in the text, the teacher explains what happens in each case.


Figure 9. The main simulation window of the switch controllers.

3. Simulation of AC static switch controllers

helping with Visual Basic's software package [1, 4, 5]:

chopper simulation using radio buttons.

• A part that contains simulation scheme.

the switch controller analyzed.

• Another part is dedicated to information area.

diagonal of a diode bridge (Figure 11) [5].

• It opens the main simulation window of the switch controllers.

Figure 8. Reversible AC switch controllers: a) Symmetrical scheme, b) Non-symmetrical scheme.

tinua) and the other to exit the application (Iesire) (Figure 9).

Press the button for the continuation of simulation (Continua).

The simulation window containing three main parts [4]:

• It launches the simulation software.

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The simulation of static switch function is realized like a Windows independent application

• In the main window, the user can choose the simulation type to be run with some radio buttons. The window also contains two buttons, one to continue the simulation (Con-

• It can choose the single-phase AC switch controller simulation, three-phase AC, or the

• The third part is the area where is dynamically getting up the waveforms characteristic to

• According to the manner of the scheme, choose the type of the single-phase AC switch controller, which can be with two thyristors, with one thyristor, or with one thyristor in

In the laboratory classes, students choose the type of the switch controller, making different simulations to understand the principle of operation in each case. During the simulation,

besides information in the text, the teacher explains what happens in each case.

It opens the simulation window of the single-phase AC switch controller (Figure 10).

Figure 10. The simulation window of the single-phase AC switch controller.

Figure 11. Choosing the single-phase AC switch controller type.


The range of variation of the single-phase converter phase angle and the current variation depends on the type of load. To observe the differences in the different tasks, in laboratory classes are being analyzed converter function with resistive, inductive, or resistive-inductive loads, and is being drawn conclusions about the current variation. During the simulation, the students change the command angle to observe the modification of the RMS voltage and current.

• The command angle may be modified using up/down arrows, being shown their values. Along the simulation, it modified the command angle of the switch controller, in order to evidence the way of voltage modification, or the current through load (Figure 14).

#### Notes

It may choose any load type in combination with any switch controller types.

The command angle of the thyristors may vary between 90 and 180, in the case choosing an inductive load (Figure 15).

In the case of choosing a resistive-inductive load, the command angle of the thyristors depends on the value that we want to establish by introducing a delay angle, changing the command angle of the thyristors being made from that value in up (Figure 16) [5].

In all three cases, if the command angle changes below or above the permissible values, the program alerts the user by an error message (Figure 17).


Figure 12. The single-phase AC switch controller window.

Figure 13. Choosing the load type.

• It chooses the single-phase AC switch controller type (e.g., single-phase AC switch con-

• It chooses the load type which can be resistive, inductive, or resistive-inductive (Figure 13) [7]. The range of variation of the single-phase converter phase angle and the current variation depends on the type of load. To observe the differences in the different tasks, in laboratory classes are being analyzed converter function with resistive, inductive, or resistive-inductive loads, and is being drawn conclusions about the current variation. During the simulation, the students

• The command angle may be modified using up/down arrows, being shown their values. Along the simulation, it modified the command angle of the switch controller, in order to

The command angle of the thyristors may vary between 90 and 180, in the case choosing an

In the case of choosing a resistive-inductive load, the command angle of the thyristors depends on the value that we want to establish by introducing a delay angle, changing the command

In all three cases, if the command angle changes below or above the permissible values, the

• It launches in running the single-phase AC switch controllers with two thyristors, with the control button (Simulare), which is then converted to the simulation stop button (Stop),

• During the simulation, the scheme dynamically changes its color, the sides what are in

• It will follow the area in which text information about the function mode of the singlephase AC switch controllers are presented (semiconductor elements that are in conduc-

• Is watching the area in which is rises dynamically the characteristic waveforms of the

• It is observed that by changing the command angle α between zero and π, the current by resistive load varies between maximum value U/R and zero. In the case of inductive load, because the current by load is a lag behind with π/2, the command angle can be varied by interval [π/2, π], and in the case of resistive-inductive, the command angle varies between

evidence the way of voltage modification, or the current through load (Figure 14).

change the command angle to observe the modification of the RMS voltage and current.

It may choose any load type in combination with any switch controller types.

angle of the thyristors being made from that value in up (Figure 16) [5].

tion, semiconductor elements direct polarized, etc.) (Figure 20).

program alerts the user by an error message (Figure 17).

which is located on the top right (Figure 18).

single-phase AC switch controllers Figure 21.

conduction at a time (Figure 19).

troller with two thyristors) (Figure 12).

128 Science Education - Research and New Technologies

Notes

inductive load (Figure 15).

φ and π.

Figure 14. Changing command angle in case of single phase switch controller.



Figure 16. The changing of command angle in the case resistive-inductive load.


Figure 17. The error message.

Figure 18. The control button (Simulare) in case of single phase switch controller.

Figure 19. Simulation scheme in case of single phase switch controller.

Figure 20. The information area of text type in case of single phase switch controller.

Figure 16. The changing of command angle in the case resistive-inductive load.

Figure 18. The control button (Simulare) in case of single phase switch controller.

Figure 19. Simulation scheme in case of single phase switch controller.

Figure 17. The error message.

130 Science Education - Research and New Technologies

Figure 21. The waveforms area for the single-phase AC switch controllers with resistive load.

For the three-phase AC switch controller, simulation is opening the window as shown in Figure 22.

And to the three-phase AC switch controller, the simulation windows are three main part formats from the first part which contains simulation scheme, the second part is dedicated to information area, and the third part is the area where is dynamically getting up the waveforms characteristic to the switch controller analyzed [5].


Figure 22. The simulation windows of the three-phase AC switch controller.

Figure 23. Choosing the three-phase AC switch controller type.

Figure 24. Changing command angle in case of thre-phase switch controller.

Figure 25. The control button (Simulare) in case of thre-phase switch controller.

Figure 26. Simulation scheme in case of thre-phase switch controller.

Figure 23. Choosing the three-phase AC switch controller type.

Figure 24. Changing command angle in case of thre-phase switch controller.

Figure 22. The simulation windows of the three-phase AC switch controller.

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The simulation of three-phase switch controller is made for different types of load and by changing the angle of the semiconductor elements. Based on information from the simulation, the students made a report on the functioning in different cases, which is then analyzed together with the teacher, being clarified with aspects of the operating principle.

Figure 27. The information area of text type in case of thre-phase switch controller.

Figure 28. The waveforms area for the three-phase AC switch controllers with resistive load.


Figure 29. The button for application exit (Iesire).

#### 4. Conclusions

In electrical devices, the AC switch controller is used for asynchronous motor speed change by changing the supply voltage and to the asynchronous motor startup by varying the voltage between zero and nominal value.

These types of static converters are used to control the voltage applied to the stator windings of a cage induction motor or to modify the effective rotor resistance of a wound induction motor. In first case, the converter is connected in series with the stator windings, and in second case in parallel with a resistance.

Using an AC switch controller is the simplest way to control the speed of AC drive systems. However, this method has some disadvantages such as low input power factor, decreasing efficiency with lower speeds, increasing losses of a drive system if the converter used modifies the effective rotor resistance.

The simulation scheme dynamically changes its color, the sides what are in conduction at a time. In the simulation window, there is a text area where information about the function mode of the converter, the semiconductor elements direct polarized or which are in conduction at that moment are displayed. The window contains also an area with buttons for changing the command angle.

Some of the simulation windows contain a pull-down menu button used to change some parameters or to choose different types of loads. All windows contain two command buttons, one for starting up the simulation (Simulare), which is transformed in button for stop the simulation (Stop) and a button to exit of the window (Iesire).

This documentation describes a Windows application, useful for understanding the functioning of the static variators, converters, and typing to cover all the needed aspects. This application has a teaching purpose, being useful for the students studying static converters.
