[ARC5] AC Motor Start Caps as Filters

[Scott Johnson]

Usually, start capacitors are non-polar electrolytics (intermittent duty)

Run caps are usually paper in oil (continuous duty)

 

Scott V. Johnson W7SVJ

5111 E. Sharon Dr.

Scottsdale, AZ 85254-3636

H (602) 953-5779

C (480) 550-2358

 <mailto:scottjohnson1 at cox.net> scottjohnson1 at cox.net

 <mailto:scott.johnson at ieee.org> scott.johnson at ieee.org

 

From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On Behalf Of Bobby Drummond
Sent: Monday, March 23, 2020 7:29 PM
To: ARC-5 Maillist <arc5 at mailman.qth.net>
Subject: Re: [ARC5] AC Motor Start Caps as Filters

 

I would agree about AC ratings versus DC ratings. That is true about many other capacitors at least.  One thing though to remember about them is some are made for more "intermittent" duty and some are meant for continuous duty (as in "start" capacitors and "run" capacitors.

 

As far as for use in DC power supplies, I am not sure.  Could be interesting though if they could be used.  Might be a handy alternative if they are OK in DC power supplies.

 

 

 

On Mon, Mar 23, 2020 at 10:21 PM Roy Morgan <k1lky68 at gmail.com <mailto:k1lky68 at gmail.com> > wrote:

I remember a report quite some time ago now from a fellow who spoke in person with an engineer at a manufacturer and asked about the dc rating of such capacitors. The engineer laughed and said the practical dc rating would be something like four times the peak of the rms ac rating. 

 

Roy

 

Roy Morgan

K1LKY Western Mass





On Mar 23, 2020, at 10:03 PM, Robert Eleazer <releazer at earthlink.net <mailto:releazer at earthlink.net> > wrote:

I was helping a friend troublshoot a 7.5 hp AC motor ... that the start caps were 1200 mfd at 125V, in series.  

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