Is this going to be adequate: MKP Power Caps

[bullpeters]

http://www.ebay.com.au/itm/CDJ-MKP-...ent&hash=item53f10962ec&_uhb=1#ht_1925wt_1137

 

[wintermute]

Hi, I fixed the link. You are going to have to give more information... adequate for what?

You will need to specify where in the PS it will be used, and probably expected load (if it is used for smoothing duties).

Tony.

 

[bullpeters]

Yeah thought so. Basically 50 uF, valve rectifier, 220 uF to OT, first stage regulated. The Bevois Valley. It's taking sometime . So yes, smoothing cap. I have a good deal on some MKP caps, 1000v, but the postage will kill me. These look cheap. Pls don't sugest electrolytics, I have considered them and I am eating my options

 

[Triodethom]

If there is a choke between the value rectifier and the second cap (220 uF) then yes or at least a resistor to control the current peaks . My preference is choke. Since these are close to you then I would use them.

 

[AndrewT]

You could try to find motor run capacitors near to you.
Available in 250Vac and 440Vac versions. considerably cheaper, since motors don't have any Audiophool parameter requirements.

 

[Pano]

The item is a Motor Start cap. For this use would Motor Run be any better? They'd cost more for the same values, right?

 

[AndrewT]

motor start are rated for short term voltage loading.

I have no idea if there is a de-rating that can be applied for continuous duty.

Check the manufacturer's datasheet for advice on changing from AC voltage rating to continuous DC voltage rating.
They are unlikely to state Vdc rating = 1.4* Vac rating

 

[Pano]

I have looked. So far can't find any DC ratings at all. Is that good or bad?

 

[bullpeters]

Yes there is a choke in between

 

[metalsculptor]

Why would you use a motor start capacitor (bipolar electrolytic) if a conventional electrolytic capacitor is unsuitable? 250V motor run capacitors often have a 600VDC rating, insulation fatigues under cyclic potentials making the AC rating considerably less than the DC rating. A 50uF 250VAC motor run capacitor is about the same size as a 1950's vintage 50uF 400V electrolytic.

 

[bullpeters]

For whatever reason I don't want to use an ectrolytic ,
The AC ripple that the capacitor will see is very small as it is preceded by a choke and another filter cap. My only concern is the dc rating under a continuos load

 

[metalsculptor]

You were talking about using a motor start capacitor, that is a type of electrolytic capacitor.

 

[bullpeters]

Sorry. I was under the impression that the capacitor was MKP, metalized polypropylene. I thought that meant non electrolytic. A "film" capacitor, one that doesn't have an electrolyt.
I am getting old, Mea Culpa

 

[AndrewT]

The link clearly states polypropylene and MKP.
The pic shows MKP.

You really need to get hold of the manufacturer's datasheet and find what the continuous DC rating is for this capacitor.

BTW, the peak voltage of maximum DC + half the ripple, is the maximum voltage that the capacitor must withstand.

 

[metalsculptor]

Looking at the ad it is clearly marked MKP but the compact size and referring to a start capacitor makes me wonder also the package is more like a motor start capacitor than a run capacitor it even has the roll crimp top typical of an electrolytic capacitor. Most polyester or polypropylene capacitors have plastic cases and epoxy end closures with either flying leads or push on terminals.
I would stay away from this without proper documentation.

 

[bullpeters]

For $12 buks I will buy three and cut one open,

 

[metalsculptor]

That's the spirit. BTW the girl on your avatar is cute.

 

[bullpeters]

Thanks. She is a crazy "akha" girl I now in chaing mai. I spend some time with her family in the hills, the golden triangle. She is indigenous to the the region. Not Thai, not Burmese, not Lao. But really nice

 

[AndrewT]

cut one open

and if it's a fake then report then to the relevant authorities with the intention of shutting down their business.
The Credit Card companies are a very strong tool to use against fraudulent Vendors.

 

[metalsculptor]

Akha, that's a new one, my first impression was that she was Hmong so not far off.