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New Voltage Divider Board for the Power Electronics Hands-on Experiential Trainer, Research and Teaching System

Introduction

The three-phase inverter circuit built in the New Power Electronics Hands-on Experiential Trainer, Research and Teaching System uses resistor dividers so that the 3-phase voltages, Grid Voltage, DC_Link and input currents can be measured and analyzed. To make things easier, we created a board that contains all the resistor dividers, screw terminals for the phase voltages, and header connectors for connecting the control signals. This board is connected to the STEVAL board via the MC-Connector.

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Here is a system diagram that shows all the components of the three-phase inverter circuit.

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The Voltage Divider Board (VDB) was designed with NI Multisim and NI Ultiboard. All the documentation can be found in the attached file, VoltageDividerBoard.zip. Here is a screenshot of the schematic in Multisim:

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And here is a screenshot of the PCB design in Ultiboard. This is a two-layer board:

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Important Notes

  • The header connectors include important ground connections that if not placed before the application is run could result in damaging or malfunctioning equipment. All resistor dividers use these grounds, so if those connections are somehow grounded (for example wiring the shared ground connection at the end of resistors 16, 17, & 18 to an external ground or the one in the ELVIS) then the connectors can be removed with no problems.
  • The traces running from the phase and power lines are thick and can handle high current (up to 5 amps to be on the safe side), but the rest are standard traces which could be damaged if the dividers are not working properly.
  • The following diagram shows the net connection for the two grounds (RED, and YELLOW). Basically all other yellow dots are through holes, pads, vias, or pins that are connected. If any of these were to be externally wired to a ground then the connectors could be removed from the board without issue.

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Connecting the Voltage Divider Board

1.      Connect the VDB to the STEVAL board via the MC-Connector, as shown below:

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Note that you can use stand-offs to hold board in place:

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2.      Place the single-row headers on the NI ELVIS breadboard as shown:

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Note: These single-row headers are used to connect the control signals (via ribbon cables) from the STEVAL board to the NI ELVIS Digital Electronics FPGA board.

3.      Build the 3-phase RLC circuit on the NI ELVIS breadboard.

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Note: Use the + line (breadboard) for V_NEUTRAL. One leg of the resistors needs to be connected to this line (see the schematic).

4.      Use a wire to connect GROUND (BB2) to GND in the RLC circuit (the line in the breadboard). This is the GND where capacitors are connected. See the previous image and the schematic.

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5.      Connect phases A, B and C from the STEVAL board to the VDB.

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6.      Repeat this process to connect the signals V-A GRID, V-B GRID and VDC LINK (STEVAL board):

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7.      Connect +15V and GND from the STEVAL board to the +15V Power Supply of the NI ELVIS breadboard (BB3):

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8.      Connect the Phases A, B and C (output of the resistor divider) to the RLC filter (breadboard):

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9.      Connect the output of the RLC filter to the VDB:

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  10.  Connect the NI ELVIS ADC to the VDB (blue connector):

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11.  Connect the ribbon cables to the single- row headers (Voltage Divider Board), as shown:

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Note: Make sure you use the top row of the dual row crimp on connector.

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The alignment is simple, top row of connector has a 1 to 1 connection with the connector at the other end of the wire. This means, for example, that the first pin from the top row on the blue line side leads to the first pin of the top row on the blue line side of the other end of the cable.

12.  Connect the other end of the ribbon cable to the NI ELVIS breadboard (single-row headers): BB2 and BB4.  Read the labels on the VDB:

BB4

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BB2

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This is the end product, rearrange and twist the connectors to open up the view of the breadboard or as you wish it to be displayed. Enjoy!

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Let me know if you have any questions.

Have a great day,

Fernando

Fernando D.
National Instruments

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