How To Select OBCDC-Link Capacitors For An 800V Platform?

(MENAFN- Market Press Release) December 10, 2025 8:54 pm - A detailed explanation of the performance advantages of Yongming CW3H series liquid snap-in capacitors.

Question Type: Voltage Withstand Requirements

Q: What are the core voltage withstand requirements for capacitors in an 800V platform DC-Link circuit?

A: The waveform and number of surge impact tests need to be clearly defined. For DV testing, it is recommended to apply bidirectional load dump pulses according to ISO 16750-2 to verify the voltage withstand and capacitance stability after hundreds of impacts, ensuring the design margin is effective.

Question Type: Ripple Capability

Q: In high-frequency switching environments, what technologies does the CW3H series use to improve ripple withstand capability? How does it perform in practice?

A: It uses a new low-loss electrolyte to reduce ESR, achieving a ripple current withstand of 1.3 times the rated value. Laboratory data: 450V 330?F (1.94mA at 120KHz), 450V 560?F (2.1mA at 120KHz), which meets high-frequency requirements. Request the supplier's rated ripple current and derating curve for the target model at the highest temperature (e.g., 105?) and actual switching frequency. The actual operating ripple should be 70%-80% lower than the rated value.

Question Type: Volume-Capacity Balance

Q: How does the CW3H series achieve "small size, high capacity" when module space is limited? What are the manufacturing process supports?

A: The design optimizes the structure through special riveting and winding processes to achieve high capacity within the same volume or a 20% reduction in volume for the same specifications. Customized processes ensure production, such as 450V 330?F (2550mm) and 450V 560?F (3050mm), adapting to limited space. Layout requires thermal simulation to optimize heat dissipation and precise design of vibration-resistant stress at fixing points.

Question Type: Lifespan Indicators

Q: Is a 3000-hour lifespan at 105? sufficient for actual automotive applications?

A: The actual operating temperature needs to be considered. Based on the principle of "lifespan doubles for every 10°C decrease in temperature," if the core temperature is controlled at 85°C, the lifespan can far exceed 3000 hours. A thermal management system needs to be established: calculate capacitor losses (I2R), design heat dissipation, and measure capacitor temperatures to ensure that the operating temperature under full load and high ambient temperature is below the target value (e.g., 90°C).

Question Type: Power Density and System Integration

Q: How is the 20% reduction in size compared to traditional products reflected in engineering?

A: System-level analysis is required. Space savings can be used to add heat sinks to reduce module temperature rise, or to provide better shielding for magnetic components, improving module power density or EMC performance.

Question Type: Storage Aging and Activation

Q: Will the ESR of liquid electrolytic capacitors deteriorate after long-term inactivity? Does the first power-on require special handling?

A: Long-term idle time may affect ESR. Besides the initial power-on "pre-forming," production testing requires "activation testing" (leakage current and ESR measurement) for modules in stock for more than 6 months. Only those passing the test can be released from production. This requirement must be written into the supplier's quality agreement.

Question Type: Selection Basis

Q: For DC-Link applications using OBC/DCDC on an 800V platform, what is the basis for recommending the two core models of the CW3H series? How can designers quickly match them?

A: We recommend the CW3H 450V 330?F (2550mm) and 450V 560?F (3050mm). The parameters (voltage, capacitance, etc.) have been verified in the laboratory, and the standardized dimensions are compatible with mainstream modules. Designers can select based on circuit capacity and installation space. For switching frequencies > 150kHz, additional evaluation is required; it is recommended to create an internal selection list.

Question Type: Mechanical Reliability

Q: In a vehicle vibration environment, how can the mechanical stability and electrical connection reliability of the horn capacitor be ensured?

A: PCB design specifies elliptical teardrop-shaped pinholes. X-ray inspection of solder joints after wave soldering (to prevent cold solder joints/cracks); during DV testing, electrical parameters must be retested after vibration, not just visual inspection.

Question Type: Safety Design

Q: In compact module design, is the pressure relief direction of the capacitor explosion-proof valve controllable? How to avoid secondary damage in case of failure?

A: The module 3D model and assembly drawing must indicate the explosion-proof valve's "pressure relief protection zone." Wiring harnesses, connectors, PCBs, and high-temperature/splash-sensitive materials are strictly prohibited within this zone; this is a hard rule.

Question Type: Cost and Performance Trade-off

Q: Under cost pressure, how to balance high-voltage electrolytic capacitors and film capacitors in DC-Link applications?

A: An LCC model (including initial cost, failure rate, etc.) should be used for comparison. For projects sensitive to total lifecycle cost or with high space requirements, the CW3H series is a superior alternative to film capacitors.

Question Type: Charging Speed??Stability

Q: The charging speed of an 800V vehicle fluctuates during home charging. Is this related to the DC-Link capacitor in the OBC?

A: Bench testing can compare the bus voltage ripple spectrum of different capacitors. If the high-frequency ripple increases, causing loop instability, the capacitor is the key factor. Also, check if the temperature at the capacitor mounting point exceeds the limit.

Question Type: High-Temperature Charging Safety

Q: During high-temperature home charging in summer, the on-board charger area gets noticeably hot. Is this related to the temperature resistance of the DC-Link capacitor? Is there a safety risk?

A: In high-temperature full-load testing, in addition to monitoring the capacitor temperature, the ripple current needs to be measured. If the current is distorted or the effective value is abnormal, it may be an early signal of increased ESR and should be used as a failure warning.

Question Type: Capacitor Replacement Cost

Q: Is replacing the DC-Link liquid capacitive capacitor expensive during repair? Is it more cost-effective compared to other types?

A: Besides material unit price, it's crucial to consider the reduced return rate resulting from improved MTBF (Mean Time Between Failures), and the reduced spare parts types and shorter maintenance time due to standardized design. These are the core cost advantages.

Question Type: Charging Shutdown and Withstand Voltage

Q: When charging 800V vehicles, some trip due to "abnormal voltage." Is this related to the withstand voltage of the DC-Link capacitor?

A: Set up a test scenario (simulating grid disturbances/load step jumps), use an oscilloscope to capture the voltage of the protection bus and the capacitor current, and analyze whether the surge voltage exceeds the capacitor's surge rating and response speed.

Question Type: Lifespan Matching

Q: The on-board capacitor needs to have a lifespan close to that of the entire vehicle. Does the CW3H series meet this standard?

A: Extract user charging behavior models from vehicle big data, convert them into capacitor operating temperature profiles, and combine this with the supplier's lifespan model for design verification.

Question Type: Vibration Effects on Capacitors

Q: When driving 800V vehicles on mountain roads or bumpy surfaces, will vibration damage the DC-Link capacitor and cause malfunctions?

A: DV testing must include random vibration of the actual circuit spectrum. After testing, functional and parameter tests should be performed, and the capacitor should be dissected to check for any vibration-induced micro-damage to the internal structure.

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