What is stray capacitance issues in power electronics?9 answersStray capacitance issues in power electronics are multifaceted and impact various components and systems, from semiconductor devices to high-voltage applications and power converters. Stray capacitances (SCs) in semiconductor device dynamic test platforms can distort switching waveforms, especially in devices like SiC semiconductors, which switch faster than their silicon counterparts. This distortion affects the accuracy of current measurement results during the turn-on and turn-off processes due to the rapid changes in collector-emitter voltage and the shunting of a portion of the total current by stray capacitance. In high-voltage applications, SCs can alter the operation of devices or circuits, potentially leading to incorrect or disastrous outcomes. Modeling SCs in high-voltage capacitive dividers has been simplified to avoid the use of complex methods, demonstrating the significance of understanding and managing SCs to ensure accurate measurements and device operation.
Stray capacitance also plays a critical role in electromagnetic compatibility (EMC) issues, such as common-mode (CM) current phenomena, where it serves as a return path for CM current, affecting the radiated magnetic field. In power electronics, the stray capacitance of components like inductors or transformer windings can lead to reduced output efficiency and increased electromagnetic interference (EMI), necessitating design considerations to mitigate these effects. Furthermore, the presence of stray capacitance in power electronic applications can limit the performance of decoupling capacitors at high frequencies, necessitating improved connection strategies to minimize the need for additional capacitors.
Stray inductance and capacitance are critical in high-speed switching circuits, influencing the design and optimization of power electronics circuits to accommodate the fast switching characteristics of modern power devices. The calculation of stray capacitance in transformers and inductors, especially with disordered windings, presents challenges due to the potential for significant errors, highlighting the importance of accurate modeling methods. In high power inductive power transfer (IPT) systems, stray capacitance significantly impacts conductive common mode noise, necessitating analysis and design strategies to suppress this noise. Finally, in MHz operation of power converters, the stray capacitances of components like air-core toroidal transformers are a limiting factor for fast switching, underscoring the need to understand the relationship between structure and stray capacitances for optimal design.
Why capacitance value decrease when current density increase?5 answersThe decrease in capacitance value with an increase in current density can be attributed to various phenomena observed in different contexts. In the study of ion removal using active carbon, it was found that the ion removal speed increases with higher electrical conductivity of the ionic solution, indicating a relationship between current density and capacitance. Additionally, in heavily doped Schottky diodes, stress-induced changes in copper species affect the depletion layer capacitance, suggesting a sensitivity to external factors like current density. Furthermore, in semiconductor devices with high concentrations of generation-recombination centers, a departure from typical capacitance behavior is observed under different bias conditions, including negative capacitance, which can be influenced by current density. These findings collectively suggest that variations in current density can impact capacitance values through diverse mechanisms.
Why can't two electrodes of capacitor device be in parallel small scale?5 answersTwo electrodes of a capacitor device cannot be in parallel on a small scale because it can lead to short-circuits between the electrodes. To prevent this, semiconductor devices can be manufactured with electrode isolation films that electrically isolate the capacitor electrodes from each other. Another approach is to use spaced electrodes with a capacitance that exceeds a threshold, or to introduce an impedance component between the electrodes that causes an absolute difference between induced voltages to exceed a threshold. Additionally, compliant electrostatic transfer heads can be used, which include interdigitated spring electrodes that are deflectable into a cavity, allowing for flexibility and preventing short-circuits. These methods ensure that the electrodes of a capacitor device are properly isolated and prevent any potential issues that may arise from having them in parallel on a small scale.
Why can't two electrodes of capacitor device be in prefectly parallel small scale?5 answersThe electrodes of a capacitor device cannot be perfectly parallel on a small scale because of several reasons. Firstly, the presence of a spaced distance between the electrodes can cause the capacitance between them to exceed a certain threshold. Additionally, the impedance component, such as a resistor or a capacitor, that is coupled between the electrodes can provide an impedance that is less than a specific threshold, while inducing a voltage difference that exceeds a voltage threshold. Furthermore, the mechanical state within a parallel-plate electrolytic capacitor is affected by the presence of metal electrodes, which impact the interfacial capacitance and exert compressive stress on the electrolyte. These factors contribute to the inability to have perfectly parallel electrodes in a capacitor device on a small scale.
What influences the occurence of faradaic or capacitive effecrts on electrodes?5 answersThe occurrence of faradaic or capacitive effects on electrodes is influenced by various factors. One important factor is the microstructure and geometrical arrangement of the electrodes. The relative position of the reference electrode with respect to the working and counter electrodes can affect the reference potential and therefore impact the overvoltage readings. Another factor is the solution conductivity, which can have an adverse impact on power generation in microbial fuel cells (MFCs) and can lead to errors in measured electrode potentials. Additionally, the type of electrode used can also influence the electrodeposition effect, with certain types of electrodes showing better results. Understanding these factors is crucial for accurately assessing and interpreting electrochemical measurements and their implications in various systems.
How to know if TV capacitor is bad?8 answers