Using hybrid capacitors in PWM controlled motor drives

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Dr. Stumpf Péter Pál
Department of Automation and Applied Informatics

The goal of my thesis was the comparison of the behaviour of aluminium electrolytic and

hybrid capacitors in electromechanical steering systems.

First, I made a review about the different properties of capacitors and I studied their

performance as a link capacitor in a 3-phase system.

Later I simulated the operation of a 3-phase inverter and I obtained the changes of the

voltage and current characteristics caused by the stepping of equivalent circuit parameter


The next step was the planning of the measurement. I measured the characteristics of

the different types of capacitor with the same set-up and as an automated process. I did

the evaluation process in Python.

In the first measurement I investigated the parameters of the equivalent circuit of the

capacitor with an LCR meter. Then I made the measurements with the ECU and the

PMSM motor using different capacitor types.

I determined the state where the biggest load appeared and then I did the measurements

at zero speed and at with a rotating rotor. I examined the different voltage and current

signals for the two types of capacitor and for different number of hybrid capacitors. The

automated processes were realized in CANape software, and allowed to interface to the

instruments and control or read the ECU.

The evaluation was implemented in Python. The results proved the advantages of the

hybrid capacitor versus the aluminium electrolytic. However, further examination of the

technical benefits is necessary to justify their usage despite their high price.


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