What is chopper in power electronics

The following DC converters can be examined:

  • Thyristor DC chopper (file download: DCSWITCH.CIR)
  • DC chopper for the 1st quadrant (file download: CHOPP-1.CIR)
  • DC chopper for the 2nd quadrant (file download: CHOPP-2.CIR)
  • DC chopper for the 1st and 2nd quadrant (file download: CHOPP-12.CIR)
  • Boost converter (file download: STEPUP.CIR)

 

Practical experiment 1: The thyristor DC chopper with quenching thyristor and ohmic-inductive load

Start with the software tool PSpice A_D the file DCSWITCH.CIR as an example of a SCR-based static dc switch.

"Oscilloscope" using the software tool sample

  • the input voltage
  • the output voltage
  • the capacitor voltage
  • the voltage across the main thyristor and the quenching thyristor
  • the capacitor current
  • the input current
  • the current through the main thyristor
  • the current through the quenching thyristor
  • the current through the freewheeling diode
  • the load current

 

Practical experiment 2: The DC chopper with the ideal switch for the 1st quadrant with ohmic-inductive load and counter voltage

Run the CHOPP-1.CIR file as an example of a first-quadrant chopper. The first-quadrant chopper can only ever produce positive output voltage and positive output current. This means that, on average, the power always flows from the energy source into the load.

Set the duty cycle (magnitude control) to M = 0.8. Determine using the software tool sample the following values ​​for the output voltage and the output current at this ratio:

  • dc component (direct component)
  • ac component (bill of exchange)
  • rms value (effective value)
  • rms value of the ac component
  • ripple factor

 

Practical experiment 3: The DC chopper with the ideal switch for the 2nd quadrant with ohmic-inductive load and counter voltage

Start the CHOPP-2.CIR file as an example of a second-quadrant chopper. The second-quadrant chopper works with a positive output voltage and a negative mean value of the output current. This means that on average the power always flows from the load into the supplying energy source (e.g. energy recovery when a tram is braking).

Set the duty cycle (magnitude control) to M = 0.4. Determine using the software tool sample the following values ​​for the output voltage and the output current at this ratio:

  • dc component (direct component)
  • ac component (bill of exchange)
  • rms value (effective value)
  • rms value of the ac component
  • ripple factor

 

Practical experiment 4: The DC chopper with the ideal switch for the 1st and 2nd quadrant with ohmic-inductive load and counter voltage

Start the CHOPP-12.CIR file as an example of a first-and-second-quadrant chopper. The first-and-second-quadrant chopper always works with a positive output voltage and a positive or negative mean value of the output current. This means that on average the power either flows from the load into the supplying energy source (e.g. energy recovery when a tram is braking) or from the energy source to the load using a motor.

Enter values ​​for the amplitude control M yourself. "Oscillograph" the voltages and currents of interest to you when operating the DC chopper in both quadrants.

Develop a PSpice circuit file for one on your own

  • first-and-fourth-quadrant chopper and one
  • four-quadrant chopper

 

Practical experiment 5: The step-up converter with an ideal switch and ohmic load

Start the STEPUP.CIR file as an example of a step-up chopper. Set the duty cycle to DRATIO = 0.75.

"Oscilloscope" using the software tool sample

  • the input voltage
  • the output voltage
  • the input current

Repeat the measurement with a duty cycle of DRATIO = 0.5.

Set the switch-on ratio to DRATIO = 0.8 and compare the DC component of the switch current with the DC component of the output current.