1. Aluminum Electrolytic Capacitors
Aluminum electrolytic capacitors are a great value. More than 80 billion—that’s “billion” with a B—were sold worldwide in 2007 and usage is growing at about 15% per year. Most are miniature capacitors in in high volume electronics. Today we’re going to talk about the larger ones that are primarily in power electronics

2. Aluminum Electrolytic Advantage
The high value capacitor choice
Typically last more than 10 years
Lowest cost dielectric for high capacitance and energy storage
4 to 10 times the capacitance per dollar of film capacitors
Great for power electronics bus capacitors to 600 V
These capacitors achieve their high value by delivering the most capacitance and energy for the price—4 to 10 times the capacitance per dollar of film capacitors. They are reliable and typically last more than 10 years without drying out or having high ESR increase. They are great as power electronics bus capacitors and are available up to 600 V.

3. Aluminum Electrolytic Principal Applications
Power-supply input capacitors output capacitors
Bus capacitors for inverters in UPS systems Motor-drives
Photoflash and Strobe Flash
Welders
The principal applications for these large can capacitors is power electronics. In AC-to-DC power supplies they are used as input and output filter capacitors. In AC-to-AC power units with inverters like UPS systems and motor-drives they are used as input bus capacitors, DC-link capacitors. Other important users are photoflash, strobe and welders.

4. Switching Power Supply Application
DC to AC power supplies are mostly switching power supplies in which the AC voltage from the power line, the AC mains, is rectified to convert it to an unregulated DC voltage. This rectified AC is applied to a DC to DC converter that chops up the voltage so that it can be processed at a high frequency, typically 20 to 100 kilohertz. That allows power voltage conversion using less expensive, smaller capacitors and transformers. Aluminum electrolytic capacitors are typically used at the input as bus capacitors and at the output as output filter capacitors.

5. Linear Power Supply Application
Transformer steps 120 Vrms down to 12.6 Vrms
12.6 Vrms AC voltage is 35.6 V peak to peak
Fullwave rectified voltage is 0 to 16.4 V
Add 200 µF capacitor: filtered voltage is 16 V with ±0.4 V ripple voltage.
Linear power supplies are more expensive because larger capacitors and transformers are needed for power voltage conversion at 60 hertz, the power line, AC mains frequency. So, linear supplies are limited to precision supplies in which the switching noise is a problem and small supplies where a switching requlator is deemed too complicated.
The linear supply shown here is a simple linear power supply. The 120 volts AC input voltage is stepped down to 12.6 volts AC by an input transformer as shown by the –17.8 volt to volt sinewave at the top and labeled “Secondary AC Signal.” If the 200 microfarad filter capacitor were not in the circuit, the fullwave rectified signal across the resistor load would be the zero volt to 16.4 volt varying DC voltage shown. If we put the capacitor in the circuit as shown, it filters the voltage and smooths it to the about 16 volt DC voltage with a couple of volts of ripple voltage on it. The ripple voltage causes ripple current to flow in the capacitor.
With the capacitor in the circuit the rectifying diodes only conduct when the load causes the voltage to droop enough to be less than the 120 Vac input voltage. Thus the diodes only conduct at the peaks of the AC input voltage.

6. Ripple Current is King Ripple is from rectification and switching
Ripple current heats the capacitor (blue peaks below)
Higher temperature shortens capacitor life
But operating life claims and calculation methods are not standardized, so the capacitor maker with the best models, technology, and technical sales force has an advantage
Notice that the ripple current is made up of the light-blue peaks shown in this waveform. They occur when the load voltage—the light green waveform—falls to less than the rectified AC input voltage, the purple waveform. This variation in load voltage, the ripple voltage causes ripple current to flow in the capacitor.
And understanding ripple current is key to the successful application of aluminum electrolytic capacitors. While in a linear power supply the ripple current is entirely from rectification of the power line AC mains voltage, in switching power supplies there is also ripple current from the high-frequency switching in the DC to DC converter.
The ripple current heats the capacitor and shortens the capacitor’s life. How much ripple current a capacitor can take and how long it would last are the important questions.

7. Temperature Rise
The temperature rise DT is the thermal resistance q from the capacitor core to ambient times the power P DT = qP = qI2(ESR)
To lower the temperature rise lower thermal resistance q lower power P
How much ripple current is answered by determining how hot the capacitor gets. How hot it gets is determined by how much power the ripple current creates in the capacitor, and how well the capacitor can get rid of the heat. The ability of the capacitor to get rid of the heat is determined by its thermal resistance.
The temperature rise, shown here as delta T, is the thermal resistance from the capacitor core to ambient times the power from the ripple current. Thermal resistance is shown here by Greek letter, theta. Its units are degrees C per watt. So, if one watt of power heats the capacitor 5 degrees C, then the thermal resistance is 5 degrees C per watt.
The power is the ripple current squared times the load resistance. Current often has the symbol I and the power would be I squared R. The R in capacitors is often expressed as ESR, equivalent series resistance.
To lower the temperature rise we can lower the thermal resistance and we can lower the power dissipated. And lower temperature means longer capacitor life.

8. Lowering Temperature Rise
Lower thermal resistance q with Thermal Pak capacitor construction
Lower power P with lower ESR from new electrolytes, separators & foils
You can lower q with capacitor choice and cooling with a fan or heatsink
And so to lower the temperature rise we can
Lower the thermal resistance with the capacitor construction,
Lower the power with lower ESR in the capacitor
Lower thermal resistance with cooling using a fan and/or a heatsink

9. Thermal Pak™
Compression Design with extended cathode, low thermal resistance
Better shock and vibration
Safety vent can’t be blocked by tar
Lighter weight
ThermalPak is a good way to lower the thermal resistance with capacitor construction.
The compression mounting on a plastic peg in the molded top and an aluminum peg in the can bottom combined with extended cathode foil delivers a solid metal-to-metal connection with the capacitor element, and makes it run cooler by having the can at the same temperature as the capacitor element. Other advantages of ThermalPak are that it has better mechanical shock and vibration withstanding and compared to units with potting compound such as tar, it’s lighter weight and has no risk of the safety vent being blocked by tar.

10. Extended Cathode Handles High Ripple Current
Extended cathode foil at right gets heat out
Cornell Dubilier has offered three standard constructions in screw-terminal capacitors—Potted, Rilled and ThermalPak. Potted is no longer offered for environmental reasons. Extended cathode foil assures that the capacitor element stays cool. Rilled has the capacitor element captured by spoon-shaped dimples in the can called rills. It provides the best vibration and shock withstanding. And ThermalPak is the generally preferred construction because it is not limited to full can designs.
Double Peg Compression
Potted
Rilled

11. CDE Expected Life Calculator
Allows you to predict life with your operating conditions
Calculates temperature rise and expected life for screw terminal capacitors snap-in capacitors
Accurate—Based on extensive thermal measurements of capacitor materials
I’ve said that to know how long a capacitor will last you need to know how hot it gets. Cornell Dubilier’s Expected Life calculator does that and more. It allows you to predict expected life with your operating conditions. It allows you to calculate temperature rise and expected life for Cornell Dubilier’s screw terminal, snap-in and plug-in capacitors. Plug-in capacitors are a variation of screw terminal capacitors with tops with three plug-in copper pins instead of screw terminals.
The calculator is accurate because it is based on extensive thermal measurements of capacitor materials and life tests.

12. The following is a CDE Calculator Comparison of 550C to DCMC
Both in 3 inch diameter by 5⅝ long cans
550C is 3700 µF, 450 V
DCMC is 5600 µF, 450 V
Both 20 amps of ripple current at 360 Hz
Both 25 amps of ripple current at 2 kHz
Expected lives: 550C about 20 years, DCMC about 1 year.
The next slide shows two calculators on the screen. It compares the performance of a Type 550C inverter grade 105 degree C capacitor to a same-size Type DCMC low-cost screw terminal capacitor. The 550C has only 3700 microfarads at 450 volts, while the DCMC has 5600 microfarads at 450 volts.
Both capacitors are running at 450 volts with 20 amps of 360 hertz ripple and 25 amps of 2000 hertz ripple thus simulating a harsh switching application with ripple current from rectification and from powering a DC to DC converter or inverter load.
The results show that the 550C would last about 20 years and the DCMC about one year

13.
Here’s how the two calculators look on the screen. To activate you would select the 550C and DCMC using the Type pull down menus. You’d select 450 volts as your rated dc voltage on both calculators. You’d select diameter 3 and length on both calculators. Click search catalog on both calculators, and up comes your capacitors. Enter your ripple currents and air temps. Click calculate on both calculators, and see that the 550C has an expected life of 176 thousand 300 hours and the DCMC has an expected life of 9 thousand hours. In years that’s a little less than 20 years and a little more than one year.
The calculator permits you to adjust ESR and capacitance values for custom ratings and include MTBF and FIT reliability calculations.
Printable Form allows you to capture the data as a text file.

14. Screw Terminal Capacitor Types
Now let’s look at the Cornell Dubilier screw terminal aluminum electrolytic capacitors.

15. Type 550C, The 105 °C Inverter Capacitor
The top of the line inverter grade capacitor is Type 550C and rated for 105 degree C operation.

16. Type 550C, The 105 °C Inverter Capacitor
Longest life, highest ripple current type
Standard of comparison
200 V to 450 V, inverter voltage range
Compares with UCC LXR Series
Special specifications, part number 550CExxxx
The Type 550C has the longest life and the highest ripple current capability. It’s intended for bus capacitor applications so rated voltages are 200 volts to 450 volts volts is also now available. The Type 550C can operate more than hours at rated voltage and temperature. That’s equivalent to more than thirty years at 65 degrees C.

17. Type 520C, The 85 °C Inverter Capacitor
High value, high ripple current type
The next step below Type 550C
200 V to 500 V, inverter voltage range
> 80% of Type 550C ripple capability
Compares with UCC RWF Series Rifa PEH 105 °C
Type 520C is the inverter grade capacitor rated 85 degrees C. It’s lower cost and has more than 80% of the Type 550C’s ripple current capability. It too is for bus capacitor applications and has rated voltages from 200 to 500 volts.

18. Type 500C, Long-Life Capacitor
Twice the life of Type DCMC
6.3 V to 500 V, wide range
> 60% of Type 550C ripple capability
Compares with CDE Type Aerovox Type CG Rifa PEH °C
The Type 500C is for long life applications and has more than 60% of the ripple current capability of the Type 550C. It is a general purpose capacitor and has voltage ratings from 6.3 to 500 volts. New Type 500R has much higher ripple current capability.

19. Type DCMC, Best Value Capacitor
General purpose, first-choice low cost
6.3 V to 550 V, widest range
150% of Type 550C capacitance
> 40% of Type 550C ripple capability
Compares with CDE Type Aerovox Type CGS UCC U36D Series
The Type DCMC is the best value capacitor and is the choice for all applications except ones where you are trouble because you need longer life or higher ripple current capability. Like the Type 500C it is a general purpose capacitor and is offered in voltages from 6.3 to 550 volts.

20. Typical Hi-Ripple Lifetimes 4700 µF 450 V Comparison 60 °C, 12 A @ 120 Hz, 400 V
Type
Case Size
Life
Price
(in)
(years)
(%)
DCMC
3x5⅛
4.6
100
500C
3x5⅝
9.5
110
520C
23.7
130
550C
3½x5⅝
48.8
142

21. The Snap-in Capacitors
Industry’s widest selection including
New Type SLPX 85°C, 3000 h, low cost
New Type SLP 105°C, 3000 h, low cost
25% smaller Types 380LQ & 381LQ
25% more ripple Type 381LR, 105°C
4 & 5 pin Types 382LX and 383LX
We offer a wide selection of snap-in capacitors. Our new Types SLPX and SLP offer the best value. Other types are available in more compact sizes, more ripple current capability and larger sizes with 4 or 5 pins that give reverse-proof mounting and better mechanical strength.

22. Type MLP, Flatpack Capacitor
Less than ½ inch tall 20 joules of energy storage Easy to stack into modules Easy to heatsink Great at cold to –55 °C
Welded seal, flat capacitor can replace multiple snap-ins in high ripple aps
New, 450 V. Now available 7.5 to 450 V
Double the ripple capability with a heatsink
50-year life with nearly hermetic seal
MLS with stainless case, 100 year life
The square peg capacitor for the square holes in electronics. The MLP is easy to stack into high-capacitance modules for power hold up. It’s easy to heatsink and double the ripple current capability. 250 volt and lower voltage ratings operate to –55 degrees C. The welded seal delivers 50 year life and Type MLS with a stainless case delivers 100 years of life and 60% higher ripple current capability.

23. Next
Remember CDE Cornell Dubilier as your source for aluminum electrolytic capacitors
Enjoy the benefits of the life calculator at
Go to major distributors for CDE Cornell Dubilier capacitors.
It’s been great sharing Cornell Dubilier’s aluminum electrolytic capacitor capability with you.