Safety Ceramic Capacitor Solutions for EV Powertrains

Introduction

Electric vehicles (EVs) have the concerns of long charging times and short driving ranges, which are challenges for widespread adoption.  In order to solve those problems, weight reduction of vehicles and increase of battery voltage are becoming more popular. Murata has a wide lineup of high-voltage, and compact electronic components that meet these technological trends. Our lineup of safety capacitors are featured in this technical article.

xEV and safety capacitors

Safety capacitors are widely used in EVs.
The main applications for EV are OBC (On Board Charger), Traction inverter and DC-DC converter. Safety capacitors are used in those applications as a common-mode noise filter and isolation.
The following figure is shows a typical EV circuit. The capacitors highlighted in red require safety certification.

Figure 1: Applications requiring safety capacitors - EV charging technology

Safety capacitors Solution

We have been continuously expanding our lineup of IEC60384-14 X1/Y2 class certified safety capacitors in accordance with AEC-Q200, utilizing our experience and cutting-edge technology gained over many years in the automotive market.

Figure 2: IEC60384-14 X1/Y2 Class Certified DE6 Series

The DE6 series are safety standard certified lead type disc ceramic capacitors for through-hole mounting. This series is rated at 300 Vac, 1000 Vdc with a range of capacity values from 100 pF to 4.7 nF. And this is certified as IEC60384-14 X1/Y2 class.
Compared with film capacitors this series is smaller and can support high-temperature operation.

Figure 3: Space-saving, High-capacitance KCA series

The KCA series is a metal terminal type multilayer ceramic capacitor. Compared with the conventional safety capacitors, this series has a very small part size, which saves mounting space.
The KCA series is a safety certified capacitor, and possible to reflow, which can increase the design flexibility and productivity.

In addition, features such as low ESR (Equivalent Series Resistance) and low ESL (Equivalent Series Inductance) of multilayer ceramic capacitors contribute greatly to noise suppression.
It is an IEC60384-14 X1/Y2 class certified safety capacitor with a voltage rating of 250 Vac, 1000 Vdc and a range of capacitance values from 100 pF to 10 nF.

Figure 4: ESL and ESR Characteristics of DE6 and KCA Series

Figure 5: Structure of a metal terminal joined to an external electrode of a chip

One of the major advantages of choosing a metal terminal type multilayer ceramic capacitor is that the elastic action of the metal terminals greatly reduces the stress on the ceramic element.
It is confirmed that the KCA series did not break even when the deflection of the substrate reached 6 mm in the substrate bending resistance test, and the solder crack did not occur even after 2,000 cycles in the temperature cycle test^*. The risk of failure due to vibration is also reduced.

*The product warranty differs from the test conditions based on the AEC-Q200 by a deflection of 5 mm and 1000 cycles, respectively.

New series of safety certified capacitors for automotive

We introduce a new product, the EVA series.
The EVA series is a safety standard certified resin mold surface mount type ceramic capacitor. This is compatible with the high voltage 800 V battery system of xEV. It features a high rated voltage of 1500 Vdc and a creepage distance of 10 mm.
This new product retains the advantages of surface mount, small size, and low ESL characteristic of the KCA series, while achieving the long creepage required by safety standards for high-voltage systems.
The EVA series is an IEC60384-14 X1/Y2 class certified capacitor with a voltage rating of 305 Vac, 1500 Vdc and a range of capacitance values from 100 pF to 4.7 nF.

Figure 6: Securing 10mm for both creepage distance and clearance distance (outside bent part)

Figure 7: ESL and ESR Characteristics of DE6 and KCA Series

Conclusion

Safety certified capacitors are essential components for xEV systems to reduce EMI and withstand lightning surges.
The safety certified capacitors introduced in this article are new solutions that meet the expectations of EVs.

If you have any questions based on this article that you would like to discuss with an expert at Murata, don't hesitate to reach out. There's an entire team ready to support you with your question.

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