Dave,
Where are my Rectifiers or the Money for them???
I sent you them over 3 Months ago, Still waiting.....
Boyd
-----Original Message-----
From: Dave Kirkby <davek@medphys.ucl.ac.uk>
To: <carsten.esch@olympus-software.com>
Cc: amps <amps@contesting.com>
To: <amps@contesting.com>
Date: Friday, August 14, 1998 6:10 AM
Subject: Re: [AMPS] Bleeder Resistor
>
>Carsten Esch wrote:
>
>> Hi,
>>
>> I am wondering about 'the' bleeder resistor in a 4kV DC - 1A power
>> supply (230V DC input), must of the designs I found are using a 50uF
>> capacitor and something like 100k/250W bleeder.
>> Is there any disadvantage to use a 400k instead? I remember something
>> like up to 100 Ohm per volt is ok? Would be nice not to dissipate too
>> much power in the bleeder... Any comments?
>>
>> Carsten, DL6LAU
>>
>
>I would be tempted to put two resistors in parrallel. If one goes, you
>have a backup.
>
>Obviously the larger the resistor(s), the longer it takes to discharge
>to a safe value. If you start with 4 kV, and consider 50 V safe, then it
>needs to fall to -log_base_e(50/4000)=4.4 time constants before its
>safe.
>
>Using 50uF and 400k, has a time constant of T=C.R=50e-6*400e3=20 sec.
>Hence it would be safe after 20*4.4=88 seconds.
>
>If you have lots of electrolytics in series, then you need the resistors
>to equalise voltage drops too, but I suspect from that you are using one
>big cap, as you talk of using one high value, high wattage resistor.
>
>G8WRB
>
>
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>
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