Welcome to the KEMET Specifying Electrolytic Capacitors Product Training Module. This presentation will discuss how to specify electrolytic

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2 Welcome to the KEMET Specifying Electrolytic Capacitors Product Training Module. This presentation will discuss how to specify electrolytic capacitors according to the design requirements, the ways operating life is given in the datasheets and how that is used for estimating life in your application, and how a more detailed life calculation is done for demanding power applications. 2

3 First we will discuss the specification of small electrolytics for general purpose applications. One typically chooses either SMD or radial lead capacitors as needed. For larger capacitance, snap-in capacitors are also available. These electrolytics are specified by first identifying the capacitance and voltage. If the requirement is sensitive to the ESR or ripple current, they are also specified. Next, the nominal and maximum ambient temperatures are identified, as is the desired life at the nominal temperature. Usually for general purpose capacitors one then finds a catalog item meeting the specifications. It is a straightforward process except that the life of the selected capacitor must be estimated. 3

4 Typically the life of an electrolytic capacitor is given at maximum temperature. A good rule of thumb for general purpose applications is to double the life for every 10 degrees of temperature reduction. For example if one requires a life of 50 thousand hours at an ambient temperature of 55 degrees C, a capacitor with eight thousand hours life at 85 degrees will suffice. A capacitor rated for two thousand hours life will not do. 4

5 Also note that the life of an electrolytic capacitor often varies by size. Be sure to read the datasheet carefully to obtain the rated life for the specific size of interest. 5

6 KEMET offers several options for SMD electrolytic capacitors including low ESR and long life versions. 6

7 In radial lead electrolytics there are a number of options to match the design requirements for temperature, voltage, ESR, ripple current, and life. 7

8 Longer lifetimes are available with snap-in electrolytics due to their larger size. Options are available for both general purpose and power applications, the latter also offering higher ripple currents. 8

9 In power applications, the operating temperatures are often elevated, and high ripple currents flow through the capacitor. KEMET snap-in and screw terminal capacitors are designed to perform well in these conditions. The electrolytics are in many cases operated closer to their specification limits. Therefore a more accurate calculation of the life under the specific operating conditions is called for. It is critical to have an accurate simulation or measurement of the nominal and surge voltages, components of the ripple current, and the nominal and max ambient temperatures. It is common for KEMET to optimize a capacitor design for specific applications to better match all the required parameters. 9

10 A detailed life calculation requires knowing the capacitor ESR at any given frequency and temperature, the thermal characteristics of the capacitor, and the relationship of life versus hotspot temperature for that series. These are all contained within KEMET s online life calculator. When considering a power electrolytic capacitor, use the double the life for every 10 C decrease rule just to make sure you are in the right range. Then enter your operating conditions into the online calculator, found on the next slide, to get an accurate operating life. If a suitable capacitor cannot be found, an optimized solution may be the answer. Kemet has the capability of adjusting the parameters of the capacitor to meet special needs. 10

11 To use the Kemet online life calculator, begin by entering the capacitor type and parameters. Then click List Capacitors. Blank fields will result in more options. 11

12 A list of options will appear below. Click Calculate Life for the capacitor of interest. In this example the first capacitor will be chosen. 12

13 Enter the actual operating voltage, typical ambient temperature, airflow, and components of the ripple current. Then press the Calculate Life button. 13

14 The life and other operating conditions will be displayed. 14

15 KEMET power electrolytic capacitors are mechanically constructed to maximize operating life. The lid and sealing system reduce electrolyte diffusion out of the can. Multiple welded tabs reduce ESR and internal temperature rise, thus increasing the life. The mechanical interface of the capacitor winding to the base of the can gives excellent thermal dissipation again, reducing the internal temperature rise and increasing the life. in addition, KEMET develops electrolyte solutions inhouse to provide maximum stability of the capacitor parameters over time. 15

16 The standard ranges of KEMET power electrolytic capacitors offer extremely long life to meet demanding requirements. Because the operating life can be accurately calculated it is not necessary to over rate the temperature. For example if an 85 degree capacitor meets the required life under the specific operating conditions, it is unnecessary overkill to request a 105 degree capacitor. Again, KEMET offers both standard solutions and the ability to optimize a capacitor for particular requirements. 16

17 In summary, an electrolytic capacitor is specified with more or less detail depending on the nature of the application. In particular, the operating life for general purpose requirements may be estimated from catalog data. Power applications are severe enough to warrant a more detailed life calculation based on the particular design. (Slight pause) Kemet offers a complete line of aluminum electrolytic capacitors for both general purpose and demanding power applications. 17

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