psu problem / ripple current / esr

metebalci · 29th April 2004, 01:56 PM

Hi,

Actually I have asked for this problem before in Tube forum. However, I havent found a solution yet.

I have the circuit below. V1 and R3 represents the transformer (220V to 300V, 180VA) and its equivalent series resistance (Rp=11.4ohm, Rs=16.2ohm). C1 and R2 represents the electrolytic capacitor I am using. That is a new Kendeil 05 type. R2 is max ESR specified by manufacturer (170mOhm).

I have built the circuit and also simulating on Orcad. In real circuit I am measuring 395Vdc at (+) pin of C1 and ground when there is 297Vrms in secondary of transformer. 297*1.414=420V. The first question is why I am measuring 395V instead of 420V ? (DMM is a cheap one, not a true rms device)

The graphs below is from Orcad. It seems there is a ripple current of 11A at first. Kendeil 05 is rated at 1.8A. Is it harmful for it ?

Is ESR=170mOhm low compared to other capacitors (Nichicon NT etc.) ?

Can I easily measure ESR of a capacitor ?

Thanks so much in advance.

MB

thoriated · 29th April 2004, 02:41 PM

Hi, Metebalci -

It could be your DMM, as you suggest, and/or the waveform may be somewhat flattened on top. A single half cycle of 11A shouldn't hurt the capacitor, as long as the average ripple current stays below its rated value after the initial charging surge.

slowhands · 29th April 2004, 06:09 PM

The 1.414 multiple assumes no load at all on the supply, it's just the peak voltage of the AC in. You two diode drops in your bridge, and have a bleeder resistor of 220K. It only draws a small current, about 2ma, but it reduces the average voltage a tad. There is also very very slight leakage current through the diodes and the capacitor.

Do you know the accuracy spec of your DVM? If not, compare its reading to some well known reference voltage. It may also be misleading you.

metebalci · 30th April 2004, 09:56 AM

>The 1.414 multiple assumes no load at all on the supply, it's just
> the peak voltage of the AC in. You two diode drops in your
> bridge, and have a bleeder resistor of 220K. It only draws a
> small current, about 2ma, but it reduces the average voltage a
> tad. There is also very very slight leakage current through the
> diodes and the capacitor.

Is it possible to drop 30V in diodes, bleeder resistor, leakage currents ? It seems too high to me.

DC Voltage Accuracy is %0.5, AC Voltage Accuracy is %0.8

Thanks.

MB

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Ripple current ?	woody	Solid State	2	12th January 2009 10:09 PM
ripple current calculation?	AndrewT	Power Supplies	5	30th January 2007 04:24 PM
Ripple current in capacitors.	beppe61	Power Supplies	5	3rd September 2006 11:37 AM
whats ripple current of c	johndiy	Solid State	9	2nd September 2006 11:37 AM
ripple current calculation	metebalci	Parts	1	24th July 2004 09:10 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

29th April 2004, 02:41 PM	#2
thoriated diyAudio Member Join Date: Nov 2003 Location: flyover country	Hi, Metebalci - It could be your DMM, as you suggest, and/or the waveform may be somewhat flattened on top. A single half cycle of 11A shouldn't hurt the capacitor, as long as the average ripple current stays below its rated value after the initial charging surge.

29th April 2004, 06:09 PM	#3
slowhands diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	The 1.414 multiple assumes no load at all on the supply, it's just the peak voltage of the AC in. You two diode drops in your bridge, and have a bleeder resistor of 220K. It only draws a small current, about 2ma, but it reduces the average voltage a tad. There is also very very slight leakage current through the diodes and the capacitor. Do you know the accuracy spec of your DVM? If not, compare its reading to some well known reference voltage. It may also be misleading you.

30th April 2004, 09:56 AM	#4
metebalci diyAudio Member Join Date: Feb 2004 Location: Istanbul/TURKEY	>The 1.414 multiple assumes no load at all on the supply, it's just > the peak voltage of the AC in. You two diode drops in your > bridge, and have a bleeder resistor of 220K. It only draws a > small current, about 2ma, but it reduces the average voltage a > tad. There is also very very slight leakage current through the > diodes and the capacitor. Is it possible to drop 30V in diodes, bleeder resistor, leakage currents ? It seems too high to me. DC Voltage Accuracy is %0.5, AC Voltage Accuracy is %0.8 Thanks. MB

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)