Cara-Nastasja Behrendt, M. Sc.

Research Staff Profile

• Research Topic - Common-Mode Currents in a Stator Winding
  What is your research topic and what is it about?

  The use of fast-switching power electronics increases the high-frequency components of currents and voltages in drive systems. As a result, the stator winding no longer behaves purely as an ohmic-inductive component but also exhibits capacitive characteristics. The capacitances between the stator winding and the stator core shown in the Figure provides, as described by  a preferred path for the current at high frequencies. This causes a portion of the current to flow as a so-called common-mode current  over the core to the ground, which is an undesirable parasitic effect. This raises the question of how this current can be predicted and minimized. Therefore, my research focus is on prediciting the commo-mode currents and analyzing how the design of the stator winding can be optimized to minimize the these currents without additional components.

  Why is your topic relevant?

  A key aspect of this research topic is that common-mode currents can cause significant damage to the drive system. The main types of damage include electric damage of the bearings, as illustrated in the Figure, and the insulation system breakdowns, which can can result in complete system failure.

  Preventive measures to avoid such damage often result in additional costs and space requirements. Common solutions, such as filters, increase the system's spatial and financial demands.

  Furthermore, parasitic currents lead to extra losses. 

  In the automotive industry, both the additional losses and the increased space and weight due to counter measures effect the electric vehicles range negatively, highlighting the importance of this research.