--------- Begin forwarded message ----------
From: Ron Hooper <ab4ru@stc.net>
To: km1h@juno.com
Subject: Re: [AMPS] Electrolytic Capacitor Ratings
To: <amps@contesting.com>
Date: Wed, 30 Apr 1997 22:39:18 +0100
Message-ID: <3367BC06.F0A@stc.net>
References: <19970430.145623.9671.4.km1h@juno.com>
km1h@juno.com wrote:
>
> Would some please explain why 450V appears to be the maximum rating
> available today? Many years ago 500V, 600V and even 800V were
available.
> How critical is that 450V rating? Will a CGS computer grade cap with a
> 500V surge rating run long term at 510V...with loading reducing the DC
to
> 435V?
>
I have used those type of capacitors in several power supplies. I can
not answer why 450 volts is so common. The surge is usually about 500 to
525 volts with a WV rating of 450.
I have had some problems pushing the rating to the working voltage. I
always use carbon resistors as equalizing and not the wire wound. Wire
wound have a better track recording of opening up and causing the
voltage to blow the cap. As the caps get old the capacitance changes,
dielectric breaks down a little and they go pop. With the caps running
under the WV by 20 percent it will prolong the life and give less
trouble. I have seen when a rectifier opens in a bridge and puts ac on
the caps that will blow them also, especially if at or near the WV
rating. It is rare that that happens. The only thing I have to back up
my observations is my past experiences using them. I prefer the old
sytle Oil filled without PCB's. No question about those lasting, a long
time.
Ron W4WA
--------- End forwarded message ----------
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