[Amps] HV Resistor Source

[John Lyles]

The "industry standard" for such a resistor is a pulse rated R like a Kanthal Globar. The company has changed names a lot recently, so search for them. These are carborundum bulk resistors, non inductive. You can live with inductance of a WW, of course, but in a dead short, you might find your resistor flashing over with plasma. Then it isn't such a good resistor. Globar isn't cheap, but they are excellent in this application, as well as for dummy loads. You have to study their literature, type AS and SP material. One is better for continuous dissipation and the other is best for very high peak voltages but low dissipation. They make them with clip in connectors or wires. 

73
John 
K5PRO


> Message: 8
> Date: Wed, 17 Apr 2013 00:58:47 -0500
> From: donroden at hiwaay.net
> To: Amps at contesting.com
> Subject: Re: [Amps] HV resistor source
> Message-ID: <20130417005847.27844mn5ynlr261j at webmail.hiwaay.net>
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> 
> Quoting Jim Garland <4cx250b at miamioh.edu>:
> 
> > That's going to be quite a resistor, inasmuch as 4KV across a 30 ohm
> > resistor amounts to a half million watts of dissipation!  A 4KV pulse 50uS
> > wide, once per second, would dissipate 25W.
> > 73,
> > Jim W8ZR
> 
> 
> The resistor isn't to ground..... it's in series with the tube(s) that  
> may draw 1 amp intermittently ... therefore 1 amp squared through 30  
> ohms is 30 watts.
> 
> If the tube draws more amps ... a short or a bad load... maybe a two  
> amp spike... that is 120 watts which will hopefully burn out the  
> resistor
> ( acting like a fuse ) before the transformer or diode stack goes up in smoke.
> 
> Don W4DNR
> 
> ***