Today’s aluminum electrolytic capacitors have longer shelf life, usually around 2 years, as compared to their predecessors. The owner of this blog makes no representations as to the accuracy or completeness of any information on this site or found by following any link on this site. As the table below shows, as the temperature decreases, the lifespan for solid capacitors increases. Later, the sun will cool to a white dwarf, and after … At 65 C, the average lifespan for a solid capacitor is more than six times greater than electrolytic capacitors. Other parts, like resin, have also their life, but they are 20 - 30 or over years. There are different ways to model the amount of internal temperature rise for a given ripple current. This reputation is justified if you are only looking at the rated lifespan, but the operating conditions are often much more favorable than the rated conditions. Your email address will not be published. This design lifetime can vary from as little as 1,000 hours to 10,000 hours or more. In fifteen years the electrolytic power supply capacitors will get old. The circuit required a very high voltage capacitor and so it used two 4.7uF 400V electrolytic capacitors in series, I replaced them with one 2.2uF 900V film capacitor. It would appear that the reputation of Al e-caps as unreliable devices is actually justified. This de-rating involves re-calculating the lifespan based on the actual operating temperature, voltage, and current, and often times the de-rated lifespan is many times longer than the rated lifespan. 1 Deriving Life Multipliers for Electrolytic Capacitors Sam G. Parler, Jr., P.E. The aluminum forms a very thin insulating layer of aluminium oxide by anodization that acts as the dielectric of the capacitor. Required fields are marked *. Aluminum electrolytic capacitor is the shortest life parts in power supplies. All content provided on the mathscinotes.com blog is for informational purposes only. In other words, the actual expected lifespan will be $$2^3=8$$ times more than the rated lifespan. This 30oC difference results in three doublings of the expected lifespan over the rated lifespan. Very long life (> 20 years at temperature up to 75°C) is possible to be achieved by choosing capacitors with optimized design. This means that exceeding the rated ripple current specification on an electrolytic capacitor is a very bad thing to do. © Mark Biegert and Math Encounters, 2020. Today’s aluminum electrolytic capacitors have longer shelf life, usually around 2 years, as compared to their predecessors. Once again, the lifespan de-rating calculation is. I regularly receive questions from other engineers on how to model the lifetime of electrolytic capacitors. Like all components, electrolytic capacitors eventually do wear-out (e.g. Which ones are more prone to failure under normal use? Manufacturers of electrolytic capacitors specify the design lifetime at the maximum rated ambient temperature, usually 105°C. For example, the KXG family of Al e-caps from United Chemi-Con (which includes capacitors with capacitances from 6.8μF to 330μF and voltage ratings from 160V-450VDC) has a rated life expectancy of 8,000 to 10,000 hours while the EPCOS B32798 family of film capacitors (which includes capacitors with capacitances from 18μF to 75μF and voltage ratings from 250V-400VDC) has a rated life expectancy of 60,000 hours. Operating conditions directly affect the life of an aluminum electrolytic capacitor. Practical Life Span I am assuming here that we are taking about standard wound aluminum electrolytics and the answer is it depends on operational conditions. The manufacturer will state an internal temperature rise value (e.g. It is subject to a stochastic process and can be described qualitatively and quantitatively; it is not directly measurable. For example, Vishay uses standard CECC 30301 for their Al e-caps, which defines the end of life as being when the capacitance changes by 30%, the dissipation factor changes to more than three times the upper limit, or if the impedance is more than three times the stated limit. The following five life span definitions of aluminum electrolytic capacitors are used at Elna, Ltd.: 1. But how much of that bad rap is actually deserved? The rated lifetime is measured by the capacitor's manufacturer during stress testing and is usually shorter than the capacitor's lifetime in an application. You may have heard that electrolytic capacitors are a bad choice. If the actual life calculated is still not long enough, we can determine what the actual voltage and current factors are to provide an even more accurate expected lifespan. We have had some of these power sources in the field for nearly ten years, so we are starting to see some worn-out capacitors. Both of the capacitors have a temperature rating of 105oC, so if the operating temperature is estimated at 75oC (which is high for this system), there is a 30oC difference between the rated and the operating temperature. Electrolytic power supply caps likely constitute the single worst liability in old audio, radio and test equipment. The higher the temperature the shorter the life. I have a question. I should note that the term will change sign when IA/IR > 1. But are they really that much worse? After some research to find components that meet these voltage and capacitance requirements and also have the best combination of size and cost, we find two possible solutions. My preferred form for the capacitor lifetime equation is shown in Equation 1. That number is twice as long as typical electrolytic capacitors with average life ratings of approximately 2,000 hours. Assume that we are designing an AC-DC converter for a battery charging system. Guaranteed Life Span The life span that is set in the product transactions. Guaranteed Life Span– The life span that is set in the product transactions. Notify me of follow-up comments by email. wall adapters, uninterruptible power sources) that we buy from outside sources. $$life_{actual}$$ is the life expectancy at the operating temperature, voltage, and current. I captured Equation 1 using Mathcad and plotted it assuming that: I will vary TA and the IA/IR to generate the contours shown in Figure 3. Life of aluminum electrolytic capacitor is temperature dependant and it is doubled when ambient temperature is 10°C lower, based on Arrhenius’s Law. The Expected Lifetime of Electrolytic Capacitors. Unfortunately, their lives are relatively short (~15 years) compared to oth… By combining small size and very low cost per unit capacitance, electrolytic capacitors (hereafter called electrolytics) are the only cost-effective choice for high-value applications like power supply filtering in most consumer gear. Aluminum electrolytic capacitor is the shortest life parts in power supplies. For aluminum electrolytic capacitors, the changes in ESR, capacitance, and leakage current are caused by chemical reaction between the … Depending on usage, you will begin to have semiconductor and other failures between 10 and 50 years after date of manufacture. The longer the design lifetime, the longer the component will last in a given application and ambient temperature. Figure 1). So the life on electric devices generally are not problems. Aluminum electrolytic capacitors have a reputation as having a short life expectancy and being unreliable. The basic modeling approach can be described as follows: The temperature within the capacitor is driven by (1) the ambient temperature of the capacitor, and (2) the power dissipated within the capacitor. For simplicity, let’s assume the voltage factor and the current factor are both 1 (they are both probably more than 1) and only de-rate based on temperature. (The period of time where the specified performance will be maintained.) Figure 4 show my plot. Figure 2: Graphic of Capacitor Lifetime Multipliers. The Nichcon UCY line of capacitors (PDF Datasheet) offers several desirable performance boosts: Rated for high temperatures (+105 degrees Celsius) Rated for long life (load life of 10,000 – 12,000 hours) Tolerance is a little tighter at ±20%; Rated to handle high ripple current; This capacitor … What is the life span of an electrolytic capacitor? The relationship between life and temperature follows a chemical reaction formula called Arrhenius' Law of Chemical Activity. 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