Tutorial Induction Machine.

The model of the induction machine is used throughout the book. Therefore it is important to understand the functioning of it and how to build it yourself. The blocks for building the Induction Machine are available in the Advanced Electrical Drives library and can directly be connected to each other

The model for the induction machine using the IRTF building blocks is shown below:

<br>Click to close the image

Selecting the components
The components are selected from the Advanced Electrical Drives library. This library is opened by clicking on the left side on

Components,
Library,
Advanced Electrical Drives
<br>Click to close the image Here you see a list with the available components. We start with selecting and dragging a component to the workscreen. Remember that for selection you only have to click (left mouse button) the component once. It then sticks to your mouse pointer and is placed on the workscreen by clicking on the workscreen. Parameters are supplied by clicking the component on the workscreen with the right mouse button.

Selecting components from the library
To include components from the library, open the library by clicking the + sign in front of the item or double click the item with the left mouse button. The library is organized in two sections:

  • Scalar
  • Vector
Since the Induction Machine model will be build from blocks based on space vectors, we will select only components from the vector sections in the library. The interface between the scalar and space vector format is given by the blocks Vector2Scalar and Scalar2Vector from the section "Components/Library/AdvancedElectricalDrives/Interface".

We start with the spacevector component. From the section "Components/Library/AdvancedElectricalDrives/Source/Vector" we select the component SpaceVector by clicking and releasing it with the left mouse button.
(Note! Don't keep the mouse button presssed down after the selection!)
The SpaceVector component now sticks to the mouse pointer and can be dragged onto the workscreen. Place the component by clicking the left mouse button again. You can always move the component by clicking and holding it with the left mouse button, moving the mouse pointer and releasing the left mouse button. .
The other components are selected in the same way. The components: Sub, Gain, Linverse and Integrator in the stator and rotor circuit are spacevector components and are therefore selected from the "Components/Library/AdvancedElectricalDrives/Math/Vector" section.
The blocks for the mechanical model IntegratorVariableGain and Sub are scalar models and therefore selected from the "Components/Library/AdvancedElectricalDrives/Math/Scalar" section.

The QuadraticLoadVariable component is selected from the "Components/Library/AdvancedElectricalDrives/NonLinear/Scalar" section.

The IRTF-Current block is selected from the the "Components/Library/AdvancedElectricalDrives/Transformation/Vector" section.

The waveforms are displayed in scopes in the as space vectors. In order to see the ab and xy components, the spacevector is expanded into its ab and xy components by the component Vector2Scalar that can be found in the "Components/Library/AdvancedElectricalDrives/Interface" section.

The first component we selected was the spacevector block. To have a RMS phase voltage of 230V we have to select the 3phase 400V system. The parameter for the amplitude in the space vector component is equal to the RMS value of the output line voltage. In this case we select 400 to get an RMS line voltage of 400 volts and an RMS phase voltage of 230Volts.

From the input voltage we subtract the stator winding voltage being the stator current multiplied with the stator resistance. This is done with the Sub block that is placed directly after the space vector component.

The stator flux is the integral of the stator voltage minus the stator resistance voltage drop and is calculated with the Integrator component. From this flux, we usually substract the airgap flux from the IRTF by using a Sub component that is rotated and divide the resulting leakage flux by the leakage inductance.

In this model we use the Linverse component to model the stator and rotor leakage flux seperately. The Linverse component is a vector component selected from the math section.

One output from the Linverse component is the stator current and is multiplied with the stator resistance. The stator resistance is a Gain component selected from the math section. Here we have to define the value of Rs and we have to define the label.
The label will be Rs and can be entered at the entry Label: in the properties of the component. The properties dialog box of the component is opened by either double clicking the component with the left mouse button or by simply clicking the component with the right mouse button. <br>Click to close the image

The label Rs has the same format as the label that can be assigned to nodes. The underscore _ and subscript ^ can be used only once, although both can be mixed. The greek symbols are placed between the ampersand & and semicolon; symbol. Start capital greek characters with a capital, for example, &Psi;_s^xy represents Ψsxy

The IRTF component is the rotating transformer that you can also think of being the airgap. It seperates the stator and rotor and provides the position dependend interface between the stator and rotor fluxes and currents. On the right side of the IRTF we build the rotor circuit from a Gain and Integrator component from the MathVector section.

The mechanical model is set up using scalar components. The output from the IRTF is the electromagnetic torque produced in the airgap between stator and rotor. From this Torque Te the load torque Tl is substracted.

From the resulting acceleration torque, using an IntegratorVariableGain, the angular speed and angular position is calculated. In the IntegratorVariableGain also the labels J and 1 are defined in the component properties dialog box. An initial condition for the angular speed or position can laso be defined in these integrator components.

The mechanical load of machine is defined in the QuadraticLoadVariable component that is selected from the "Components/Library/AdvancedElectricalDrives/NonLinear/Scalar" section. Here we define the load torque at a defined angular speed. The characteristic of the load component will be a quadratic function passing through zero and te defined load.

Editing component values
The properties of a component such as a numerical value, label and frame and fill color are defined in the component properties dialog box. Open the component properties dialog box by clicking the component with the right mouse button.

Rotating, flipping and moving components
The components are moved by simply clicking the component with the left mouse button. Keeping the left mouse button pressed pressed down you can drag the component over the workscreen. Releasing the left mouse button placed the component on the workscreen.

A component can be rotated and flipped. This is done by opening the components properties dialog box with the right mouse button. Flipping is done over a imagainable horizontal or vertical line. The orientation of a component is selected by clicking one of the four options 0, 90, 180 or 270.

Drawing the connections
The components are all placed and we can draw the connecions between the components. A connection is drawn by simply clicking the left mouse button on the starting node, dragging the mouse pointer to its end location, while keeping the left mouse button down and finally create the connection by releasing the left mouse button.

A connection is made from maximum two straight line segments and can contain at least one corner, which is automatically created depending on the position of the beginning and end node.

Note!

A connection is always started from a node, being an input or output from a component. Do not make connections between circuit and block diagram nodes as explained in the "Review of basic editing" tutorial. <br>Click to close the image Circuit nodes are round, block diagram nodes as used in this tutorial have a square size.

Adding labels
Labels can be assigned to nodes to identify the value of the node or to connect nodes without drawing connections. A label is edited at a node by clicking the node with the right mouse button.
To display a arrow above the label, start the label with ^
The underscore _ and subscript ^ can be used only once, although both can be mixed. The greek symbols are placed between the ampersand & and semicolon; symbol. Start capital greek characters with a capital, for example, &Phi;^&lowast;_s represents Φ*s

Note:

If two nodes share the same label they are connected although no connection line will be drawn.

Adding scopes
Use the "Scope" block to display any signal. You can insert a "Scope" in by clicking the first button on the bottom button bar. <br>Click to close the image

The component Vector2Scalar that can be found in the "Components/Library/AdvancedElectricalDrives/Interface" section is used to split the vector signal into its ab or xy components. The "Scope" can be connected to the output from the Vector2Scalar component or can be connected via connections.
For a direct connection, place the input of the "Scope" right on top of a node. You can resize the "Scope" by clicking and dragging the right-bottom corner. The number of inputs automatically increases while resizing the "Scope". <br>Click to close the image To connect the input ofa scope to a node via connection, start drawing a connection at the input of the scope and end the drawing at a node. Ending the drawing of a connection (starting from a scope input), on the workscreen will automaticall create a node with connection to the scope input. Here you can define a label that is already defined in the schematic in order to display that value in the scope.

Starting the simulation
Start the simulation by pressing the "Play" button or pressing the [Enter] key. Two parameters Tscreen and the step size dt control the simulation. The parameter "Tscreen" defines the width of the "Scope" window.

<br>Click to close the image The parameter "dT" defines the integration time step. The parameters are entered in the simulation parameters dialog box that can be opened from the menu at Simulation/Simulation Parameters

Editing component and connection colors
The background color of the connections as well as the background and frame color of the components can be defined in two ways.

In accordance with the definition in "Fundamentals of Electrical Drives", the color of the stator circuit is green, the rotor circuit is blue and the color of the mechanical model is red.


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