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AC Power Bank

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AC Power Bank

Post by mthoi on Fri Apr 05, 2013 5:16 pm

I have been doing some research after Dr Who's very positive postings on Frank's Power Bank (FPB) for audio applications. I don't have a FPB and from what I understand from Dr Who's postings, FPB is using induction to store & reserve electrical energy for transient load increase. If I remember my college electronics, electrical energy can be stored using magnetic fields (i.e. coils/transformers) or chemical (i.e. capacitors).

Lately, I have been experimenting with using motor-run capacitors to in my DIY balanced power supply circuit. Thus far, the results has been quite positive - quieter background, better bass.

I am currently using a total of 4uf and would gradually increase the capacitance in the AC circuit over time. I am keen to find the optimal capacitance over a given power load. And the preferred brands of motor oil capacitors. I am currently using Siemens MKV 1500VAC, single pole capacitors, and have ordered several ASC 386, 440VAC caps for comparison.

I am keen to hear from fellow DIYer whom have embarked on similar projects. I am reachable via PM or email at mengtaihoi@gmail.com


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Re: AC Power Bank

Post by Wikin on Fri Apr 05, 2013 9:30 pm

Interestingly I'm also about to add capacitance to my AC inlet. I've got a bulk of russian PIO 400v caps, around 22uf in total.

The perplexing thing about the Power Bank is that its inductance can actually degrade the ac power factor in the house.

Factories and power plants are actually trying hard to cure using capacitance:

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/powfac.html
http://en.wikipedia.org/wiki/Power_factor

beats me why a poorer power factor can sound better...

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Re: AC Power Bank

Post by lhgin on Sat Apr 06, 2013 7:25 am

Wikin,

It might be the balancing act between the downstream equipment connected to the mains versus the inductor from FPB. Smile It might just so happens that the inductance in FPB corrects the mains that are connected to high power systems with tonnes of capacitance. One pulls the current ahead of the voltage and the other retracts it.

Ken

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Re: AC Power Bank

Post by Wikin on Sat Apr 06, 2013 11:56 am

Yes agree with your POV Ken, it's surely a balancing act to get the power factor close to 1.0 for every home.

On a side note, while high powered hifi systems have high capacitance on their PSUs, they also have large power transformers. How does these 2 combine to affect the power factor is surely another unknown factor for most users.

Perhaps the final effect is that the capacitance effect take precedence over the inductance.

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Re: AC Power Bank

Post by kp93300 on Sat Apr 06, 2013 1:32 pm

Hi mthoi,
I build several of the Felix ac line filter from the Lab in audiocircle . seems to work well and is widely adopted by several other kaki in kuching
it is basically a common mode choke with several x2 caps on other side of the common mode choke. I use it for equipment with lower power requirements.
cheers
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Re: AC Power Bank

Post by lhgin on Sat Apr 06, 2013 1:38 pm

Wikin - really need a power analyzer to see what is the net effect of all those stuff connected on the mains.

kp9300/mthoi,

i built this and is quite effective.

http://www.diy-audio-guide.com/mains-filter.html

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Re: AC Power Bank

Post by mthoi on Sat Apr 06, 2013 2:18 pm

Dr Wong, Ken - tx for the feedbacks. I am in the midst of implementing AC filters into each of my tube amps, preamps and phono amps' power supply and do away with the AC filter at the balance transformer (pic).

I have included a pic of the balanced transformer with the Siemens MKV caps and filters. I have also got my hands on some industrial spec caps (siemens MKV) that I would like to try-out in the experiment.



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Re: AC Power Bank

Post by kp93300 on Sun Apr 07, 2013 11:24 am

I agree with ken that experimentation with different combinations of caps and balance transformer is necessary to achieve the desire effect.
After all, this is diy ! Very Happy

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Re: AC Power Bank

Post by joeling on Sun Apr 07, 2013 7:36 pm

Gents,

I just want to highlight that motor run caps have a finite lifespan. When it fails - ugly. It will take years but it will happen.

If u are into DIY you will recall more than 10 years ago TNT audio had an article on DIY parallel filters that one plugs into the socket next to the equipment. I made 2 of those & they served me for many years. One day also quite a few years ago, I smelled smoke coming from my hifi room. I thought one or all of my DIY equipment had gone up in flames. Turned out that it was the filter & specifically the cap. Burned through the plastic enclosure I used & the smell ...ewww.

Regards,
Joe Ling
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Re: AC Power Bank

Post by joeling on Sun Apr 07, 2013 7:40 pm



this one

linky
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Re: AC Power Bank

Post by Wikin on Sun Apr 07, 2013 7:58 pm

Many years back I did something similar like your Joeling, and guess what - one fine day, when thunderstorm struck, the cap actually blew up and caught fire Shocked
Since that day I always unplug my hifi mains when not in use.

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Re: AC Power Bank

Post by lhgin on Mon Apr 08, 2013 8:42 am

yup, agree with you all. unplug when not in use, no matter what! i don't like MOVs as they've a lifespan. after absorbing a certain amount of surges / energy, they will self destruct!

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Re: AC Power Bank

Post by mthoi on Mon Apr 08, 2013 4:58 pm

I second the comment on MOV's and unplugging the system during lightning storms.

8 uf seems to be the value I am going to try next.

I am now experimenting with teflon FT3 caps (russian, 630vdc) in the PSU of the amp, and zobel networks (RC) on the transformer secondaries.

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Re: AC Power Bank

Post by adrian4454 on Tue Apr 09, 2013 1:40 pm

Me too, been playing around with power factor correction device for some time now. Thanks for sharing of the danger of this stuff. My initial idea of this is to save electricity.. and even have it directly connect to main power switch for aircond. Luckily nothing did happen and I had it taken out already, as it seem to make no different in electricity bill! Ya I know, TNB does not incur cost for bad power factor correction.

But this thing done something to the hifi setup. It make the focus better, and background a bit quieter. No free lunch here, as it doesnt work in all setups.

Mine is a very simple 6uF 450VAC, resistor, and varistor, all run in parallel.

Yes, I do switch off the main fuse on the power to my setup whenever I leave the house.. I've done too many dangerous mods in my current setup~

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Re: AC Power Bank

Post by mthoi on Tue Apr 09, 2013 1:51 pm

Have a look at this site for a balanced power transformer project.

http://www.audiocircle.com/index.php?topic=18441.0



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Re: AC Power Bank

Post by mthoi on Thu Apr 11, 2013 2:20 pm

Additional reading (lots on net but similar idea) on using passive and active filters for ac power.

http://web.ing.puc.cl/~power/paperspdf/dixon/37a.pdf
http://bulletin.pan.pl/(54-3)255.pdf

Basically, passive filters uses capacitors, inductors and resistors in zobel network for power correction, storage and filtration.

Has anyone tried DIY active AC filters for audio?

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