This presentation by Sam Ben-Yaakov focuses on the selection of bus capacitors for eMobility inverters, addressing critical considerations such as ripple current, voltage ripple, and current-carrying capacity. The discussion begins with the problem of managing the AC ripple current generated by the switching of transistors in a three-phase inverter system. The capacitor bank must handle this current while minimizing voltage ripple and preventing excessive heat that could damage the capacitors. Key factors in selecting capacitors include the switching frequency, modulation type, and phase current, which significantly influence the AC ripple current. Simulations are recommended to determine the exact current values and optimize capacitor selection based on these parameters.
The presentation compares different capacitor types—ceramic, electrolytic, and film capacitors—evaluating them in terms of volume, current-carrying capacity, ESR (Equivalent Series Resistance), and cost. Ceramic capacitors excel in handling high-frequency components due to their low ESR and small size, but their effective capacitance diminishes under DC voltage. Electrolytic capacitors, while offering higher capacitance, have limitations in current capacity and are less effective for high-frequency ripple. A combination of capacitor types is suggested for optimal performance, with ceramic capacitors managing high-frequency components and electrolytic capacitors addressing larger current loads. The presenter emphasizes the importance of simulations for accurate capacitor sizing, current distribution, and impedance matching to ensure system reliability and efficiency.
Video content
- Introduction to the problem
- Ripple Current and Voltage Ripple
- AC current analysis
- Simulation results
- Frequency component analysis
- Capacitor types and comparisons
- Design considerations
- Voltage dependence of ceramic capacitors
- Figure of Merit
- Simulation emphasis
- Conclusions and recommendations
Resources: Blog Epci
