[Amps] Resonant choke filter

[R.Measures]

On Aug 1, 2004, at 2:13 AM, Will Matney wrote:

> Richard,
> Yea, I was shooting for the 3X (460Vdc X 3) but in the Allied catalog, 
> there was a jump between 400V and 2 Kv. The X363 series from ASC goes 
> from 100 to 400 Vdc. Then the next series is the X675, which starts 
> off at 2 Kv and goes to 16 Kv. I guess they figure nobody will need 
> anything from 500V to 1.9Kv? I actually needed 1.4Kv-1.5 Kv but they 
> didn't show making it.

2kV will work. More doesn't hurt.  Not enough WV results in shortened 
capacitor life.  The 1500V screen PS in my current project uses a 10kV 
resonating cap.
end

> Needless to say, I thought that odd myself. Since you mentioned trying 
> that filter out, I looked around my shop and had a 5 Henry choke. I 
> figured just to build up a demo first using a 325 Vac transformer I 
> had here just to see how much it would clean that up using a scope to 
> check it. If I had a Polaroid scope camera to fit this Tektronix 
> scope, I'd do a before and after pic. I'll try to get a pic with my 
> digital camera if it will show the trace and graticule. Really, I'm 
> building a new HV power supply for my bench using one of those 
> transformers I have. It'll have an adjustable regulated screen and 
> bias output. I'm wanting it to prototype other projects with. I've put 
> off building the thing now for two years and just now thinking about 
> starting it =) I need to find me a good deal on two panel meters in 
> the 500 Vdc range to go on the cabinet. Not found any yet without 
> buying brand new. I might just modify a couple of surplus meters with 
> a new face plate.
>
> Will
>
> R. Measures wrote:
>
>>
>> On Jul 31, 2004, at 1:30 AM, Will Matney wrote:
>>
>>> I had started designing a resonant choke filter for a supply I'm 
>>> thinking about building and figured I would share the information 
>>> here. I was looking at using a 5 Henry choke by Hammond Mfg. and 
>>> needed to figure a capacitor for it. The formula is;
>>>
>>> C = 1 / f^2 x 39.4786 x L
>>>
>>> f = frequency in Hertz (Full Wave Rect = 120 Hz, 1/2 wave = 60 Hz)
>>> L = inductance in Henrys
>>> 39.4786 = 2^2 x pi^2
>>>
>>> So after calculating for C, I got 0.00000035 (3.5^-7) or 0.35 uF. 
>>> Looking for a suitable capacitor, I needed one above 500 Vdc.
>>
>>
>> Resonating capacitors are normally 3x the DC output V of the PS.
>>
>>> I figured on using a "metalized polyester" because they go up to 
>>> around a 16 Kv rating. I found that in the 2Kv range was the highest 
>>> that would have something close in value. 4Kv didn't have close 
>>> enough really. Under 2 Kv, there was only a 0.33 uF so I need 
>>> another to parallel which I found a 0.02 uf. Both together will give 
>>> the required 0.35 uF. these caps sell for around $7 to $8 each from 
>>> Allied Elect. which is not bad. Keep in mind though that even if the 
>>> choke manufacturer says it's a 5 Henry, it may test to be something 
>>> different. So, using a scope to test the DC output, adjusting the 
>>> value of the capacitor(s) slightly may have to be done. If so, add 
>>> or subtract enough C until the ripple goes as low as it can.
>>>
>>> Will Matney
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>> Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
>>
>>
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>
>
>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org