Question Type: Voltage Rating Requirements
Q: What are the core voltage rating requirements for capacitors in an 800V platform DC-Link circuit?
A: Confirming the voltage rating requirement is the first step in selection, but it’s necessary to clarify the specific test waveform and number of surge impacts. In DV testing, it is recommended to refer to ISO 16750-2 or equivalent standards, applying bidirectional load dump pulses (such as load dumps) to verify the capacitor’s voltage rating and capacitance stability after hundreds of such pulses, confirming the effectiveness of its design margin.
Question Type: Ripple Capability
Q: In high-frequency switching environments, capacitors need to withstand extremely high ripple currents. What technology does the CW3H series use to improve ripple current tolerance? How does it perform in practice?
A: Achieved through material innovation—using a new low-loss electrolyte, effectively reducing the equivalent series resistance (ESR), thereby increasing the ripple current tolerance to 1.3 times the rated value. Laboratory data verification shows that at 1.3 times the rated ripple current, the core temperature rise of this series of capacitors is stable with no performance degradation. In typical specifications, the 450V 330μF model achieves a ripple current of 1.94mA at 120kHz, and the 450V 560μF model achieves 2.1mA, meeting the ripple tolerance requirements of high-frequency switching scenarios. Ripple capability is core to high-frequency design and requires verifiable engineering data. It is essential to obtain the ripple current (I<sub>rms</sub>) rating and derating curve for the target model from the supplier at the highest operating temperature (e.g., 105°C) and actual switching frequency (e.g., 100kHz). During design, the actual operating ripple should be 70%-80% lower than this rating to control temperature rise and extend lifespan.
Question Type: Size-Capacity Balance
Q: How does the CW3H series achieve a balance between “small size and high capacity” when module space is limited? What are the process supports in production?
A: Reduced volume means potentially increased heat density per unit volume. During layout, thermal simulation is needed to optimize airflow or conduction heat dissipation paths around the capacitor. Simultaneously, the fixing point design for small-volume capacitors requires greater precision to prevent additional stress during vibration. This is achieved through process innovation on the design side—using special riveting and winding processes to optimize the internal structure, achieving “higher capacity in the same volume” or “approximately 20% volume reduction in the same specification.” On the production side, this customized process is central; for example, the 450V 330μF specification requires only 25*50mm, and the 450V 560μF specification is 30*50mm, significantly reducing the volume compared to traditional products of the same specification, adapting to the limited installation space of the module.
Question Type: Lifespan Indicators
Q: Is a 3000-hour lifespan at 105℃ sufficient for actual automotive applications?
A: This data alone is insufficient. The core is the actual operating temperature of the capacitor. Thermal design is needed to control the core temperature of the capacitor within the OBC/DCDC module. For example, if the core temperature can be controlled at 85°C, based on the rule that the lifespan doubles for every 10°C decrease in the lifespan temperature, its actual lifespan will far exceed 3000 hours, thus meeting the vehicle’s lifespan requirements. It is recommended to establish a clear thermal management chain: from capacitor loss (I²R) calculation to module heat dissipation design, and finally, by measuring the temperature of the capacitor core or pin root using thermocouples or thermal imagers, ensuring that the capacitor operating temperature is below the target value (e.g., 90°C) under the highest ambient temperature and full-load conditions, to achieve the lifespan target.
Question Type: Power Density and System Integration
Q: How is the advantage of a 20% reduction in volume compared to traditional products reflected in engineering?
A: When evaluating the volume advantage, a system-level benefit analysis is required, not just component replacement.
A simple “space value” assessment is recommended: the 20% space saved can be used to increase the heatsink area (expected to reduce the overall module temperature rise by X°C), or to provide better shielding for more important magnetic components, thereby improving the overall module’s power density or EMC performance.
Question Type: Storage Aging and Activation
Q: Will the ESR of liquid electrolytic capacitors deteriorate after long-term idleness (such as during vehicle inventory periods)? Is special treatment required upon initial power-on?
A: “Storage aging” affects production planning, vehicle inventory management, and after-sales maintenance.
In addition to the “pre-forming” process for initial power-on, an “activation test” process should be added to the production testing station for modules that have been in stock for more than 6 months. This involves measuring leakage current and ESR after power-on, and only modules that pass the test can be removed from the production line or delivered. This requirement should also be included in the quality agreement with the supplier.
Question Type: Selection Basis
Q: For DC-Link applications using 800V platform OBC/DCDC, what is the basis for recommending the two core models of the CW3H series? How can designers quickly select the right model?
A: Standardized models can reduce management costs, but it is necessary to ensure that they cover the main application scenarios. Recommendation Basis: Both models (CW3H 450V 330μF 25*50mm and CW3H 450V 560μF 30*50mm) cover the core requirements of the 800V platform. Key parameters such as voltage, capacity, size, lifespan, and ripple resistance have been verified in the laboratory, and their dimensions are standardized to fit mainstream module installation spaces.
Selection Logic: Designers can directly select the appropriate model based on circuit capacity requirements (330μF/560μF) and the module’s reserved installation space (2550mm/3050mm), without additional structural adjustments, while simultaneously meeting the requirements for high current withstand, long lifespan, and cost optimization. Besides voltage and capacity, please pay close attention to the resonant frequency and high-frequency impedance curves of the two models. For designs with higher switching frequencies (e.g., >150kHz), additional evaluation or customization with the supplier may be required. It is recommended to create an internal selection list and use these two models as the default recommendations.
Question Type: Mechanical Reliability
Q: In automotive vibration environments, how can the mechanical stability and electrical connection reliability of capacitors (such as horn capacitors) be ensured?
A: Mechanical reliability must be guaranteed through both design and process control.
PCB design guidelines clearly stipulate that horn capacitor lead holes must be elliptical teardrop-shaped, and X-ray inspection of solder joints must be performed after wave soldering or selective wave soldering to ensure no cold solder joints or cracks. In DV testing, electrical parameters must be retested after vibration, not just visual inspection.
Question Type: Safety Design
Q: In compact module designs, is the pressure relief direction of the capacitor explosion-proof valve controllable? How can secondary damage to surrounding circuits be avoided in the event of capacitor failure?
A: Safety design reflects the controllability of failure modes and must be respected in the overall system design.
The “pressure relief protection zone” of the capacitor explosion-proof valve must be clearly marked on the module’s 3D model and assembly drawing. No wiring harnesses, connectors, PCBs, or materials sensitive to high temperatures/splashes are allowed within this area. This is a mandatory design rule.
Question Type: Cost vs. Performance Trade-offs
Q: Under cost pressure, how should high-voltage electrolytic capacitors and film capacitors be balanced in DC-Link applications?
A: Cost-performance trade-offs require quantitative analysis based on specific project objectives.
It is recommended to use a simplified LCC model that includes factors such as initial cost, expected failure rate, associated damage costs, warranty costs, and brand damage for comparison. For projects sensitive to total cost over their lifecycle or with extremely high space requirements, high-performance electrolytic capacitors like the CW3H are usually the best engineering alternative to film capacitors.
Question Type: Charging Speed Stability
Q: When charging 800V vehicles at home, the charging speed sometimes fluctuates. Is this related to the DC-Link capacitors in the OBC (On-Board Charger)?
A: Charging stability is a system-level performance indicator. The root cause needs to be identified as either the capacitors or the control loop.
In bench testing, under the same input/output conditions, try comparing the bus voltage ripple spectrum after replacing capacitors with different batches or brands. If the ripple (especially at high frequencies) increases significantly and causes loop instability, the criticality of the capacitor is verified. Simultaneously, check if the temperature at the capacitor mounting point exceeds the limit.
Question Type: High-Temperature Charging Safety
Q: In hot summer weather, when charging with a home charging station, the onboard charger area gets noticeably hot. Is this related to the temperature resistance of the DC-Link capacitor? Is there a safety risk?
A: Reliability under high temperatures is the focus of testing and verification, not just theoretical concerns.
In high-temperature full-load endurance testing, in addition to monitoring the capacitor temperature, it is recommended to add real-time monitoring of the capacitor ripple current. If the current waveform is distorted or the effective value is abnormally high, it may be an early signal of increased capacitor ESR, which needs to be studied as a failure warning.
Question Type: Capacitor Replacement Cost
Q: During repair, I was told that the DC-Link capacitor needs to be replaced. Is the replacement cost of this type of liquid horn capacitor high? Is it cost-effective compared to other types of capacitors?
A: Replacement cost is part of after-sales and manufacturing costs and needs to be considered from the entire process.
When evaluating, it’s crucial to consider not only the unit price of materials but also the reduction in warranty-period return rates resulting from improved Mean Time Between Failures (MTBF), and the reduction in spare parts types and repair time due to standardized design. This is the true cost advantage.
Question Type: Charging Interruption and Withstand Voltage
Q: For 800V vehicles, some never interrupt charging, while others occasionally experience charging interruptions due to “abnormal voltage.” Is this related to the withstand voltage performance of the DC-Link capacitor?
A: “Abnormal voltage” interruptions are a result of the protection mechanism and require reproduction and analysis of the root cause.
Build a test scenario to simulate grid disturbances (such as voltage spikes) or load steps. Use a high-speed oscilloscope to capture the bus voltage waveform and capacitor current just before the protection is triggered. Analyze whether the surge voltage exceeds the capacitor’s surge rating and the capacitor’s response speed.
Question Type: Lifetime Matching
Q: As an automotive component, I need the capacitor’s lifespan to be close to that of the entire vehicle. Does the CW3H series meet this requirement?
A: Lifespan matching needs to be based on calculations from actual usage data, not just nominal values.
It is recommended to extract typical user charging behavior models (such as fast charging frequency, duration, and ambient temperature distribution) from vehicle big data, convert them into capacitor operating temperature profiles, and then combine them with the lifespan model provided by the supplier for more accurate lifespan estimation for design validation.
Question Type: Vibration Effects on Capacitors
Q: Will frequent driving of 800V vehicles on mountain roads and bumpy surfaces damage the DC-Link capacitor, leading to charging or power failures?
A: Vibration reliability needs to be verified during the DV stage to avoid later market issues.
Vibration testing, in addition to frequency sweep, must include random vibration testing based on real road spectra. After testing, functional testing and parameter measurements should be performed. More importantly, the capacitor should be dissected and analyzed to check for micro-damage caused by vibration to the internal winding structure and electrode connections.
Question Type: Cost-Effectiveness
Q: Compared to traditional high-voltage electrolytic capacitors and film capacitors, what are the practical advantages of choosing the CW3H series in terms of cost and performance?
A: Cost-effectiveness is the core decision-making basis for engineering selection and requires multi-dimensional data support.
Establish a “Competitive Product Benchmarking Table” to quantitatively score CW3H capacitors against similar electrolytic capacitors, polymer capacitors, and film capacitors in key dimensions such as capacitance per unit volume, ESR per unit cost, high-temperature lifespan, and high-frequency impedance. Combine this with project weighting to form objective selection recommendations.
Question Type: Replacement Compatibility
Q: I was previously using capacitors of the same specifications from other brands. Can I directly replace them with the CW3H series?
A: Replacement compatibility relates to the convenience and risks of production line switchover and after-sales maintenance.
Before introducing a replacement, a complete Direct Validation Test (DVT) must be performed, including electrical performance, temperature rise, lifespan, and vibration, to ensure that the performance is not lower than the original design. At the same time, assess whether the PCB hole diameter, creepage distance, etc., are fully compatible to avoid process issues during production or maintenance.
Question Type: Installation Requirements
Q: Are there any special process requirements or precautions when installing CW3H series capacitors?
A: The installation process is the final step in ensuring reliability and must be written into the work instructions.
The SOP should clearly state: 1) Visually inspect the capacitor’s appearance and leads before installation; 2) Specify the torque for tightening the fixing clamps; 3) Check the solder joint fullness after wave soldering; 4) It is recommended to apply fixing adhesive to the base of the leads (the compatibility of the adhesive’s chemical composition with the capacitor casing needs to be assessed).
Problem Type: Troubleshooting
Q: What should be done if abnormal temperature rise or performance degradation of the capacitor is found during use?
A: The troubleshooting process should be standardized to quickly determine whether the problem is with a component or the system.
Develop an on-site troubleshooting guide: First, measure the capacitance, ESR, and leakage current of the faulty capacitor and compare them with the datasheet; second, check the surrounding circuits for signs of overcurrent or overvoltage; third, conduct comparative tests on the faulty component and a good component under the same conditions to reproduce the problem. The analysis results should be fed back to the supplier for feasibility analysis (FA).
Post time: Dec-11-2025