[Milsurplus] AN/GRR-5 Power Supply Questions

[WF2U]

The information presented in the Handbook shows you that too little
information can be misleading (in this case not dangerous)...
Some dielectrics can be voltage dependent as far as characteristics go and
that'll affect the capacitance somewhat.
In case of electrolytics, as they're not in any way frequency or timing
determining elements, there is really no bearing of the variation as to the
tolerance of the capacitor element in the circuit. Electrolytics are rated
for capacitance tolerance of +/-20% or thereabouts (typically -20%/+10% ),
the bottom line with low voltage is not going to be less than the minimum
value within the tolerance. This, for all practical purposes in an AC
component filtering application, is negligible.

As it happens, I used to make my living for many years as an Electrical
Engineer...

73, Meir WF2U
Landrum, SC

> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net]On Behalf Of Neil Barnett
> Sent: Tuesday, August 22, 2006 4:55 AM
> To: milsurplus
> Subject: Re: [Milsurplus] AN/GRR-5 Power Supply Questions
>
>
> ----- 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
>
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>