Hello friends, today in this article you will know about what is pi filter? what is a pi filter, you are going to get very important information on this subject. so let’s start
what is pi filter?
When an additional capacitor is used in the choke input LC filter, a more stable DC voltage is obtained. This type of filter is called -filter because its frequency is the same as ‘π’.
In this, the output of the rectifier is fed to C1. Hence it is also called capacitor input filter and is used with the half-wave. For a half-wave rectifier, the value of C1 and C2 is 32uF and the value of L is 30 henry. Halfwave rectifier has a ripple frequency of 50 Hz. Thus inductive reactance,xL=1000 and capacitive reactance,xc = 9492Ω is L and reactances of C2, a.c. Acts as a voltage divider, reducing the ripple voltage by 100/9492 times its original value.
The ripple frequency in a full-wave rectifier is 100 Hz. Therefore a T-filter designed for half-wave rectifiers will reduce ripple from the output of full-wave rectifiers with high efficiency.
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In other words, for a given value of ripple, relatively small components can be used in the filter circuit in this case C1=C2 =8uF and L=15 henry. Because the value of the electrolytic capacitor is very high, there is less space to occupy. For this purpose, both the capacitors are made in the same metal container. The metal vessel automatically acts as a common ground for both capacitors. The main disadvantage of -filter is that its cost, weight, and size are high. To eliminate this loss, a series resistance of 100 to 200 is used instead of a series inductor.
Then this filter is called capacitor input RC filter, but due to the voltage drop in the resistance vessel in this filter, the output voltage decreases and the voltage regulation gets spoiled, apart from eliminating the heat generated in the resistance of the RC filter. It also requires adequate cooling. As a result the RC filter only allows those devices to be DC. Used to provide power whose operating current is very low.
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