I performed simulations of wireless power transfer in matlab simulink. It was powered with DC voltage which was then converted into a rectangular voltage with a frequency of several dozen kHz. The figures show a schematic diagram and a graph of the voltage obtained at the inverter output (red) and the voltage obtained at the L1 coil (black).

  1. Why are there voltage surges in the voltage obtained on the coil? I noticed that these jumps occur when switching pairs of transistors in the inverter and that, the difference between the two sinusoids forming the voltage on the coil is the value of the set voltage.

  2. Why is there a phase shift between primary and secondary voltages in this system?

I apologize in advance if this question has already been asked on the website or it is common knowledge that I did not assimilate. Please help.

Schematic diagram

Red-inverter output voltage, Black-L1 voltage


V3-measuring voltage at the inverter output (yellow) V1-capacitor voltage measurement (red) V2-measuring coil voltage (blue)

enter image description here enter image description here


Because you are measuring the voltage directly across R and L, the capacitor acts like a short circuit for the square wave drive voltage edges and, those "edges" pass through to R+L unhindered; just like in this simulation of a tuned RLC series circuit that I "threw together": -

enter image description here

Why is there a phase shift between primary and secondary voltages in this system?

If the two coils are not perfectly tuned (or if they are but are close together) you will have a detuning effect that produces significant phase shifting. It's not a problem.

  • \$\begingroup\$ Thank you for your answer. The resistance introduced in series was to symbolize the resistance of the L1 coil. When the resistance value of this coil changed, the length a did not change in the simulation. So what is the reason for this vertical shift of the part of the sine wave? It seems that the voltage obtained on the coil was equal to the voltage on the capacitor shifted by the value of the voltage at the output of the inverter. \$\endgroup\$ – john Jun 5 '20 at 8:30
  • \$\begingroup\$ Which nodes did you measure between and what probing method did you choose? \$\endgroup\$ – Andy aka Jun 5 '20 at 8:36
  • \$\begingroup\$ In the edition of the question I added how I measured individual values and simulation results from the program. The voltages were measured after the time the values settled (0.0225) and for a time equal to two voltage periods (2.5e-5). Coil resistances are low in the order of e-3. \$\endgroup\$ – john Jun 5 '20 at 10:01

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