Capacitors for Power Electronics

[Ref

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[Products

1. CBB137

100uF 100V 4mohm, metalized polypropylene film cap, 최소 700개, 개당7불

https://topmayelectronic.en.made-in-china.com/product/RCynNsjYSokH/China-Cbb137-100UF-100V-Metallized-Polypropylene-Film-Capacitor.html

2. 250V 47uF 오디오 무전극, $19.51

https://ko.aliexpress.com/item/1005002337665781.html?spm=a2g0o.productlist.0.0.e9ee4ec48eOFrD&algo_pvid=c35b63c4-e7ad-4bed-96df-a59ff99f4488&aem_p4p_detail=202108052159373689901043862880007063009&algo_exp_id=c35b63c4-e7ad-4bed-96df-a59ff99f4488-3

3. 800V 10uF, DC-Link, PP film, $5.56,

https://ko.aliexpress.com/item/4000318662128.html?spm=a2g0o.productlist.0.0.e9ee4ec48eOFrD&algo_pvid=c35b63c4-e7ad-4bed-96df-a59ff99f4488&algo_exp_id=c35b63c4-e7ad-4bed-96df-a59ff99f4488-16

3b. 800V, 40uF, dc-link, $11.14, 10개

https://ko.aliexpress.com/item/4000318008752.html

4. 400V 200UF 36,000원, 최소주문 56개

https://kr.mouser.com/ProductDetail/WIMA/DCP4G062007KD4MSSD?qs=RB4whv9F6rw68Rexa3vOBg%3D%3D

5. Wima, 100uV, 500V, 35*50*42* 1.9mohm, 2.9만원, DCP4H161007J, Wima; 재고 24개

https://kr.element14.com/wima/dcp4h161007jd4kssd/cap-100uf-500v-film-radial/dp/3296196?st=wima%20film%20capacitor%20100uf

6. Panasonic, 100uF, 500V, 35*56*56, 4.7mohm, 2.4만원

https://kr.element14.com/search?st=film%20capacitor%20100uf

7. TDK, 450V, 200uF, P50*95, 4mohm, 1.8만원, 재고 없음

https://kr.element14.com/epcos/b32320i8207k000/cap-200uf-800v-film-wire-leaded/dp/3649215?st=film%20capacitor%20200uf

8. TDK, 450V, 260uF, P50*120, 5mohm, B32320I4267K000, 2.1만, 재고없음

https://kr.element14.com/epcos/b32320i4267k000/cap-260uf-450v-film-wire-leaded/dp/3649208?ost=film+capacitor+260uf&cfm=true

9. KEMET, 500V, 100uF, 1.8만, 재고없음

https://kr.element14.com/kemet/c4aqlbw6100m3mk/cap-aec-q200-100uf-500v-film-radial/dp/3778510?st=film%20capacitor%20100uf

10. KEMET, 100uF, 2만, 재고없음, 0.0002

https://kr.element14.com/kemet/c4aqiew6100a3bj/cap-aec-q200-100uf-800v-film-radial/dp/3680011?st=film%20capacitor%20100uf

11. TDK, 100uF, 1.9만

https://kr.element14.com/w/search/prl/results/2?st=film%20capacitor%20100uf

1. 요약

ㅇ 탄탈륨 커패시터 ESR 100uF 20V 45mohm > 너무 높음

ㅇ 전해커패시터: 1kHz 이하에서 사용, ESM 0.3 ohm으로 높음

ㅇ 300-3kV 전력용 커패시터는 polyester film 커패시터가 주로 사용됨. 정전용량에 비례하여 크기가 커지며 가격도 개당 10-100만원으로 고가임.

ㅇ 세라믹 MLCC 커패시터: TDK 제품이 대표적. ESR 작음 (1-10 mohm). 내압 작음(25V for 100uF, 100V for 22uF), 바이어스 전압에 따라 C가 0.8-0.5배로 감소

[ESR

2. DC-Link Capacitors

ㅇ 기능

- Low impedance path for high-frequency switching currents: output filter for input stage

- Means for energy storage

- Input stage: rectifier or PFC circuit

ㅇ 선정

- Capacitance: based on ripple voltage

- Ripple current: heating

- ESR: heating

- Operating conditions: voltage, temperature, power output, line frequency, switching frequency, lifetime

1) Capacitance

- Low power AC-DC w/o PFC: allowed mains (DC mains) ripple voltage, 2uF/W

- High power AC-DC with PFC: hold-up or ride-through time on input power loss. Capacitor terminal voltage is high. Less than 1uF/W.

th*Pc/eta = 0.5*C*V1^2 - 0.5*C*V2^2

th*Pc/eta : energy required by the load during hold-up. th = hold-up time, Pc=output power, eta = efficiency

right-hand side: capacitor's discharged energy

For AC output inverters, hold-up may not be an issue and a minimum capacitance is just needed to be low enough impedance at the inverter switching frequency to minimise voltage ripple.

In practical circuits, the ripple current that the capacitor must handle without overheating by dissipation in the ESR is often the overriding factor.

The current can be so high that for a given voltage, a minimum physical size of capacitor is required to achieve low ESR, high dissipation and long lifetime.

This often leads to a capacitance which is well over the minimum from line ripple or hold-up calculations.

The ripple current waveform is very difficult to predict as it is a combination of line frequency and input and output stage frequencies and their harmonics.

The wave shapes depend on the topologies of the stages and can vary from triangular, high-rms currents in discontinuous mode PFC stages to more square-shaped currents from following bridge converter or inverter stages.

The input and output stage currents are sunk and sourced respectively from the capacitor and are not necessarily in phase or at fixed frequency, complicating matters further. There are schemes however where the input and output stages can be synchronised to achieve some ripple current cancellation in the capacitor.

From calculation, experiment or simulation, headline capacitor specifications can be found but then practical considerations of size, cost, lifetime and reliability matter.

A designer will see that there are several types of capacitor which are available for the application, splitting between aluminium electrolytic, film and ceramic types.

The choice is not easy to make and depends strongly on the application but the general trade-off is that electrolytics are cheaper and smaller than film and ceramic types for a given combination of voltage rating and capacitance (CV ratio) but have lower ripple current rating.

They also have higher variation of capacitance, ESR and ripple current rating with time and temperature and have a shorter lifetime, heavily dependent on temperature and applied voltage.

Electrolytics are only available up to about 600 VDC rating compared with several kV for film types, requiring series connection of electrolytics with balancing networks in high voltage applications.

The initial cost of an electrolytic can be very much less than that of a film type with the equivalent CV ratio. Examples would be the B43544 series electrolytic (right) and BMKP 3277 series film types from TDK EPCOS. At 470/480 µF 450V, the film type ESR is about sixty times lower, the ripple current about nine times higher and the life about four times longer at similar temperatures and frequencies. However, the electrolytic is ten times smaller and about one tenth of the cost.

Table 1 gives a summary of the main specifications of the two examples. Perhaps more important is the way the specifications of the two types vary with the environment and application conditions.

Figure 2 shows how the capacitance, loss factor and life of typical electrolytic and film capacitors vary with temperature. End of life of a capacitor is defined as degradation of performance down to a particular level, typically a variation of capacitance of greater than 20% from initial value, a dissipation factor change of more than 1.3 times initial value or leakage current greater than initial specified limit. If this cannot be tolerated and the component is used at high temperature, it may be necessary to change it out many times during the life of the end equipment with the associated purchasing, rework and down-time costs.

There is clearly a major difference in life time between the two types but during the expected life of an electrolytic capacitor, its inherent reliability is actually not too different to film or ceramic types. TDK -EPCOS quotes 10 FITS (failures in 109 operating hours) at 0.5 Vrated and 40 ˚C for the example film capacitor and although the company does not quote a figure for the electrolytic in its data sheet, typical field failure rates of 0.5 to 20 FITs have been reported for electrolytics in general. Under voltage stress, film types do have the advantage that they are to an extent self-healing and can take higher surge voltages than electrolytics.

Ceramic DC-link capacitors such as the CeraLinkTM range (left) from TDK EPCOS are only available currently up to capacitances of about 20 µF at 500 V (part B58033I5206M001) but if 23 were paralleled to achieve a comparable 460 µF at 192 cm3, they would promise potentially huge ripple current handling. Each one is rated at 31.5 A at 100 kHz, 85˚C so 23 together would handle a staggering theoretical 724 A. Like with other ceramic capacitors, however, the capacitance and ESR value does vary strongly with applied voltage and temperature.

To summarise, the choice of capacitor type is very dependent on the application, and electrolytics are still a very good option when cost is sensitive and the environment is not harsh. When temperatures and ripple currents are high, opting for an electrolytic instead of film can be a false economy when considering the costs of a shorter life leading to expensive replacement and down time. TDK EPCOS has a wide choice of both capacitor types suited for harsh conditions and in various mounting formats.

Avnet Abacus has developed a new interactive tool help you navigate TDK’s range of products for inverters and drives. Use the tool to explore the individual stages of a drive circuit and identify the most suitable products for your design. Click here to go straight to the DC-Link section, where you can access datasheets and technical information for the products mentioned in this blog and more. Alternatively, if you have any questions about DC-link circuits, or you would like to discuss your inverter design in more detail, get in touch with our product specialists.

B58033I5206M001 : 8.5만원 on Mouser

[Ref

efficiency, dc-dc converter

https://www.maximintegrated.com/en/design/technical-documents/app-notes/4/4266.html

[Capacitor selection

https://www.powerelectronics.com/technologies/passive-components/article/21857500/exploring-output-capacitor-impact-on-dcdc-converter-performance

Ceramic

Tantalum

Niobium

Aluminum electolytic

tantalum-polymer, tantalum (MnO ₂ with single- and multi-anode constructions), niobium oxide (MnO₂), multilayer ceramic, and aluminum-electrolytic.

Some 99% of the ‘design’ problems associated with linear and switching regulators can be traced directly to the improper use of capacitors,” claims the National Semiconductor IC Power Handbook.

Frequency dependence of capacitance ESR and stability with operational temperature and dc bias voltage are the important parameters of output capacitors that define performance and functionality of the complete power system.

Maxim MAX1537

In the case of tantalum-polymer and tantalum-MnO₂ multi-anode capacitors, there is a relatively small drop in capacitance in frequencies from 10 to 100 kHz (Fig. 4), whereas tantalum-MnO ₂ and aluminum-electrolytic capacitors exhibit a larger drop across the same range. The actual capacitance of the MLCC capacitor suffers due to its dependence on the dc bias voltage, which was applied during measurement. Fig. 5 shows the very low ESR performance of the MLCCs and relatively low ESR of the tantalum-polymer devices. The ESR of aluminum-electrolytic capacitors is relatively high over the complete measured frequency range.

Both tantalum single- and multi-anode capacitors retain a higher capacitance at higher frequencies (above 100 kHz), whereas niobium oxide and aluminum-electrolytic capacitors lose their capacitance faster at lower frequencies (Fig. 7). The MLCCs exhibit very low ESR around the 100-kHz frequency range; tantalum multi-anode and tantalum-polymer capacitors show low ESR in the same frequency range; and the aluminum-electrolytic capacitor has a high ESR over all frequency ranges.

1) Article reading

https://www.specterengineering.com/blog/2019/9/7/dc-link-capacitor-selection-for-your-inverter

Film or Electrolytic?

Because, the ripple current ends up being the driving requirement, most modern inverters use film capacitors. Compared to electrolytics, film caps have high ripple current rating due to their low ESR and ESL. Electrolytics have a higher capacitance/volume ratio than film caps, but the ESR and ESL is much higher so you need to put many of them in parallel in order to satisfy the ripple current requirement. The volumetric efficiency typically ends up being much higher if film capacitors are used. Additionally, the working lifetime rating of electrolytics is around 10k hours, whereas for film it’s 100k hours [1]. This is because the electrolyte dries out and leads to increased ESR which increases power loss and ultimately results in failure.

Ripple current requirement

Ripple voltage requirement

Equation (10)