[Milsurplus] AN/GRR-5 Power Supply Questions

[James Duffer]

I like it when an answer includes the reference plus some clarification.  
Thanks for straighten that issue out.  I had heard that applied voltage has 
some affect on capacitance of electrolytics.

Jim de wd4air


>From: Neil Barnett <neilba at clear.net.nz>
>To: milsurplus <Milsurplus at mailman.qth.net>
>Subject: Re: [Milsurplus] AN/GRR-5 Power Supply Questions
>Date: Tue, 22 Aug 2006 20:54:30 +1200
>
>----- Original Message ----- From: "WF2U"
>
>>ABSOLUTELY not true! The voltage rating of electrolytic capacitors, just
>>like that of any other capacitor indicates the insulation level between 
>>the
>>two electrodes which form the capacitance.
>
>Electrolytics differ from ceramic, polyester, and similar capacitors
>in that they *require* an applied DC voltage to form and maintain
>the dielectric, in a complex chemical action.  If you don't apply a
>certain minimum DC voltage, the electrolytic capacitor won't reach
>its rated capacitance.  To ensure that it does, the applied voltage
>should be not less than about two-thirds of the marked Working
>Voltage.
>
>>"Forming" an electrolytic capacitor also has
>>nothing to do with "attaining their full capacitance".
>
>Here's what the ARRL Handbook (1995) says:  "The actual
>dielectric is a very thin film of insulating material that forms on one
>set of plates through electrochemical action when a dc voltage is
>applied to the capacitor."   (page 6.9).
>
>And, "Electrolytics should not be used if the d.c. potential is well
>below the capacitor working voltage."   (page 10.5).
>
>And the 1992 Handbook says:  "A dielectric is "formed" by the
>voltage applied to the capacitor.  As a consequence, electrolytics
>should not be used where the dc potential is well below the capacitor
>working voltage."   (page 26.22).
>
>73 de Neil ZL1ANM
>
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