Source: Automotive Electronic Hardware Design
The previous article told a method of teaching how to find the parameters of ceramic capacitors. We will talk about aluminum electrolytic capacitors.
ESR parameters of ordinary aluminum electrolytic capacitance
Manufacturers generally have various series of electrolytic capacitors, low ESR, long life, high temperatures. Standards are the lowest performance, or the cheapest, general temperature and life parameters are 85 ° C / 105 ° C -1000H / 2000H. It is also this aluminum electrolytic capacitor.
The loss angle normal value is the ratio of the active power and reactive power. When the frequency is low, such as 120 Hz, the sensing resistance can be ignored, so the loss angle formula can be obtained:
Ordinary aluminum electrolytic capacitors can't find the value of the ESR in the specification, but there is a loss of angular loss angle, we can calculate, but this calculation can only be at 120 Hz, because in high frequency, ESL cannot be ignored, the formula is not applicable.
However, I found a universal electrolytic capacitor of Nichon Nichicon. The ESR of the electrolytic capacitance decreased with frequency increase, and the change rate is not large. ESR changes from 120 Hz to 100kHz, ESR only reduces half (if seen) I will find that the ceramic capacitor will fall by about 100-1000 times) as shown below.
Below is the most common aluminum electrolytic capacitance parameters of several brands, and the ESR values of 120 Hz are calculated as follows:
We can see that if we limit the value and withstand voltage, the ESR of each manufacturer is not large.
In addition, it is also possible to find that the encapsulation (size) is different, the impact on ESR will not be too large, but it will affect the size of the ripple current, which is more likely to understand, large, can be more resistant, and the ripple current is natural. The greater it.
The size of the ESR of aluminum electrolytic capacitance of different capacities and different voltages is higher.
Since each family is almost, it will take a form of ruby, and a form is column for query, as shown below.
What needs to be explained is that this ESR value is in the case of 120 Hz. If the frequency is raised, the ESR will decline in accordance with the file of Nichon Nichicon, and the curve (in front of the article) is about 2 times (100kHz), but I also found the file provided by NIPPON, and ESR dropped more, reaching 7 times.
The following figure is the curve of NIPPON
So, we can know that the normal electrolytic capacitor is more than 120 Hz, but it will be lower in the 100kHz or other frequency ESR, how much is it, and it is not certain.
LOW ESR aluminum electrolytic capacitor
In fact, aluminum electrolytic capacitor manufacturers generally provide multiple series of models, applied in different occasions, the above standard series is only one, such as the following picture is the plurut of the aluminum electrolytic capacitance series, quite rich, we will choose from I.e.
Let's take a look at how low the ESR of Low ESR's electrolytic capacitance?
Panasonic FT Series 100UF-16V Electrolytic Capacitor ESR Query Specifications 0.36 ohms, and the table standard series is 2.6 ohms, or a small.
Nikon's UCD Series 100UF-16V Electrolytic Capacitor ESR query specification is also 0.36 ohms, and the low ESR capacitance corresponding to Taiwan Lelon is 0.44Ω.
In this regard, the same size of each manufacturer low ESR aluminum electrolytic capacitor, the ESR value is not large, all of which are about seven or eighth.
About ESR first, in fact, aluminum electrolytic capacitors still have many characteristics, such as relationship between capacitive capacity and temperature, relationship between ripple current and temperature, relationship between ESR and temperature, etc., these are our hardware Engineers should know.
In addition, there may be some practical applications, such as this:
In the DCDC boost circuit, such as output 48V, I want to use electrolytic capacitors filter, because the voltage is too high, the ceramic capacitance capacity is not too big, the price is very expensive, the electrolytic capacitor can not use standards? After all, the electrolytic capacitance of LOW ESR will be more expensive. Or use a small little ceramic capacitor + standard electrolytic capacitor mixing? How to analyze this problem? Read more
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