[Amps] Bleeders

[Carl]

Without knowing the AC impedance of the transformer its just a lot of 
guessing.

Old style iron designed for tube rectifiers is often quite high and requires 
a choke input plus a low value bleeder to limit the initial current AND 
voltage spike.

With big SS diodes such as a 1N5408 or 6A10 in the same configuration (FWCT 
assumed) the choke can be eliminated and the bleeder increased BUT an input 
step start is mandatory. BUT the transformer impedance hasnt changed and the 
no load to full load regulation may be very poor. More bleeder current may 
help as excessive C causes its own problems.

Just measuring the primary and secondary DC resistance can give you an idea 
what to expect. Modern iron has very low values.

Carl
KM1H


----- Original Message ----- 
From: "Rob Atkinson" <ranchorobbo at gmail.com>
To: <amps at contesting.com>
Sent: Thursday, March 01, 2012 6:33 AM
Subject: Re: [Amps] Bleeders


> Because in some cases you need a continuous small load on the h.v.
> power supply.
> Rob
> K5UJ
>
>>> Why not skip the bleeder entirely, and make a current discharge 
>>> circuitry when the session is over.
>>> If the anode voltage is very high then stack some thyristors and fire 
>>> them with opto couplers.
>>> So when you hit the big switch it turns off all power to the power 
>>> supply, except for the auxillary
>>> circuit that keeps the draining alive and then shut off .
>>> Not very compicated to do and you get rid of the bleeder heat.
>>> Alf OH2QM
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