Authors

• Byamba Wicki

• Celina Spiess

• Sven Achermann

• Philippe Viarouge

• David Cajander

• Angelo Chrabieh

• Wolf Peter Jean Philippe

List of Figures

• Figure 1: Complete electrical diagram

• Figure 2: Methodology for transitioning from a three-phase circuit topology to that of a single-phase circuit

• Figure 3: Topology of the transformer

• Figure 4: State of the switches and configurations of single phase loads

• Figure 5: State of the switches and configurations of three phase loads

• Figure 6: Network and Transformer tab & Passive Loads tab

• Figure 7: Example 1 of the user interface of the “Network and Transformer” tab

• Figure 8: Example 2 of the user interface of the “Network and Transformer” tab

• Figure 9: User interface of the “Oscilloscope” tab

List of Tables

• Table 1: Control switches and LED status indicators for the fuses in “Network and Transformer”

• Table 2: Control switches in the “Passive Loads” tab

• Table 3: Control switches in the “Network and Transformer” tab

• Table 4: Control switches in the “Oscilloscope” tab

1. Introduction: Describing the main contents of the laboratories

The purpose of this virtual laboratory is to assimilate and apply theoretical knowledge. In particular, it involves understanding how processes work, implementing devices and equipment, using instrumentation, and processing measurements.

The laboratory aims to facilitate the acquisition of knowledge and the conduct of experiments by providing a guiding framework that allows students to focus on the experiment’s subject without initially having to worry about all the components needed for the experiments.

This virtual laboratory is designed to provide exercises to improve the understanding and mastery of the fundamental principles of electrical engineering . Laboratory exercises are an essential complement to the theory. They allow students to experiment with various circuits and applications. Therefore, users can take advantage of this virtual simulator to understand their behavior with varying levels of complexity.

This courseware will cover the following subjects:

1. Single-Phase Systems

2. Three-Phase Systems

3. Single-Phase Transformer (Coming soon)

4. Three-Phase Transformer (Coming soon)

5. Harmonics (Coming soon)

2. Description of the Virtual Laboratory

2.1 General Electrical Diagram

The overall electrical diagram of the laboratory can be configured interactively using contactors, as shown in Figure 1 below. It provides the ability to adjust the voltage source in either single-phase or three-phase mode, whether it is balanced or not, with adjustable or non-adjustable harmonic components. Additionally, it is possible to control the tension engagement angle. Transformers supplied by these networks undergo standardized identification tests, such as short-circuit tests and no-load tests.

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Figure 1: Complete electrical diagram

The main elements of the laboratory are as follows:

• A three-phase network with three adjustable sources for both the fundamental and harmonics.

• A circuit breaker with adjustable parameters.

• A transformer that can be deactivated by short-circuiting it or by creating an open circuit.

• Two blocks of series and parallel resistors.

• Six measurement points for voltage, current, and power for each phase. There is also the Fortescue transformation of the network.

• Contactors to create different circuits, with lamps to indicate open and closed switches.

This interactive display of the electrical diagram with lamps indicating open and closed contactors allows the user to quickly grasp the structure of the entire laboratory circuit. This diagram enables the creation of both single-phase and three-phase circuits.

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Figure 2: Methodology for transitioning from a three-phase circuit topology to that of a single-phase circuit

2.2 Different Types of Configurations

In general, there are three components that can be modified to achieve the desired circuit and scenario.

2.2.1 Network

The network is designed so that you can adjust the frequency, amplitude, and phase shift of each phase. The voltage source operates in either single-phase or three-phase mode. Furthermore, the network’s measurement values are displayed directly.

The network is equipped with a circuit breaker, which is part of the standard protection equipment. It allows for circuit interruption in case of overload or short circuit. Generally, it consists of a thermal trip and a magnetic trip. In this laboratory, a functionality has been added to trip the circuit breaker if the voltage drops below a certain threshold.

2.2.2 Transformer

Experiments can be conducted with a transformer by configuring it in various ways to achieve the desired setup. When it is not in use, it is short-circuited, and passive loads are supplied power without the transformer. In this case, the windings are isolated to avoid interfering with the rest of the circuit. By also short-circuiting the loads, short-circuit tests can be performed.

2.2.3 Passive Load

a) Single Phase

There are six branches of passive loads available, each consisting of a series RLC load and a parallel RLC load, as well as three passive loads in the neutral wires. These loads can be modified and arranged based on the state of the contactors and Figure 2 to create different couplings. As mentioned, when the single-phase option is chosen, the additional sources are automatically grounded and nullified for single-phase couplings. The different possible single-phase couplings are illustrated below:

b) Three-Phase

There are six branches of passive loads available, each consisting of a series RLC load and a parallel RLC load, as well as three passive loads in the neutral wires. These loads can be modified and arranged based on the state of the contactors and Figure 2 to create different couplings. The different possible three-phase couplings are illustrated below:

3. User Interface Panels

The tabs constitute the interactive interface of the virtual laboratory, which includes access to settings, measurement displays, and the electrical diagram. This interface allows users to manually control the virtual laboratory by modifying network and protection settings, assembling the electrical diagram, and observing measurements.

The user interface screen is divided into two distinct parts. On the left side of the screen, there is a control panel with several sub-windows selectable by tabs:

• A Network and Transformer sub-window “Network and Transformer” that allows control of the operating modes and settings of power supplies, the transformer, grounding connections, and circuit breakers.

• A Passive Loads sub-window “Passive Loads” that enables control, adjustment, and configuration of the six passive loads.

On the right side of the screen, there is a control panel with several display sub-windows selectable by tabs:

• An “Oscilloscope” sub-window with interactive display settings for the respective measurement points.

• A Measurements and Calculations sub-window “Network and Transformer” displaying the specific topology of the ongoing experiment, measurement displays, settings, and the spectrum analyzer display.

• A “Help” sub-window that allows the user to understand and visualize the wiring of the ongoing experiment at any time by displaying the status of different contactors on the overall electrical diagram.

This section serves as a comprehensive reference for the features of the components present on the user interface screen.

3.1 Transformer and Circuit Breaker Tab

Figure 6 displays the user interface for electrical supplies in virtual laboratories. It provides interactive options to adjust the fundamental settings of power supplies, such as frequency, amplitude, and phase shift for each phase, along with buttons to enable or disable various operating modes.

3.1.1 Network

In the network settings, frequency, voltage, and phase can be defined using input fields or sliders. The network can be set as a single-phase network, and the phases can be defined as balanced. In case the phases are unbalanced, the voltage and phase shift of phases B and C can be independently modified. Using a button, the network can be energized.

3.1.2 Transformer

There are three different modes for the transformer branch: short circuit, open circuit, or transformer.

3.1.3 Circuit Breaker

The rated current of the circuit breaker can be adjusted, and there are three different thermal modes as well as a choice of four magnetic modes. Three lamps indicate the status of the circuit breaker and the fault that triggered the protection. If the circuit breaker has tripped, its control needs to be reactivated.

3.1.4 Overview of the Panels

3.2 Passive Loads Tab

The user interface for passive loads used in virtual laboratories is presented in Figures 4 and 5. It includes interactive adjustment devices for resistances, inductances, and capacitances for each phase, as well as buttons to enable/disable balanced coupling mode for three-phase loads. When the “Balanced Circuit” option is activated, it is not possible to adjust phases B and C. Additionally, the “Star grounded” button can be selected but is not used in this protocol.

In this tab, the circuit configuration can be chosen. If in the “Measurements and Calculations” tab the “Automatic Tab” button has been selected, the complete configuration is made automatically. There are eight different automatic configurations:

• Open circuit

• A1 + B1//C1

• A1//C1

• A + B//C

• H bridge

• A1//B1 + A2 + B2//C2

• A//B

• Short circuit

There are four different components to adjust: Z_1_series, Z_1_parallel, Z_2_series, and Z_2_parallel. In the following exercises, only Z_1_series and Z_1_parallel will be used. For each phase (A, B, C), there is an impedance (series or parallel) to adjust, and there are 8 different adjustment possibilities: Short circuit, open circuit, R, C, L, RC, RL, and RLC. Depending on the choice made, the selected value can now be entered in the corresponding window.

3.2.1 Overview of the Panels

3.3 Measurements and Calculations Tab

In the “Network and Transformer” tab, the currently configured circuit is displayed. The voltage source, transformer, and passive load are visible, along with various measurements. There is a button for “Automatic tab.” When this is activated, no manual modifications can be made to the diagram.

For each element, you can choose whether it is a single-phase or three-phase circuit. In the transformer section, you can select the desired option here, which can also be done in the “Network and Transformer” tab. In the impedance section, different options can be selected, similar to the “Assembly” selection in “Passive load.” Additionally, the measurement locations are highlighted in red.

The measurements are displayed in the lower part. On one hand, there’s the Fortescue transformation of the network, and on the other hand, there are four different measurement displays. For each display, there are 20 different options to choose from, corresponding to the respective phase. The corresponding measurement points are visible in the “help” tab.

3.3.1 Overview of the Panels

3.4 Oscilloscope Tab

To observe the time-domain waveforms of different signals measured in steady-state and transient conditions in the virtual laboratory, a 4-channel digital storage oscilloscope with a generic triggering system is available. It is equipped with a 4-channel spectrum analyzer and allows for adjusting measurement, phase, and gain for each channel.

The controls of the oscilloscope are as follows:

• Channel and signal selection for measurement.

• Selection of measurement signals from a predefined list.

• Individual gain adjustment for each channel.

The “Trigger” function has the following controls:

• Trigger adjustment.

• Selection of the signal source used for triggering.

• Selection of the triggering mode (Normal or Single Sweep).

• Selection of the rising or falling edge of the signal source used for triggering.

• Selection of the signal source level used for triggering.

3.4.1 Overview of the Panel

3.5 Help Tab

The complete electrical diagram is visible in the “Help” tab. Furthermore, for each configuration, lights illuminate to indicate the current connections. This allows for visual tracking of the setup.