Re: [TCML] Variac Problem!

[Mark Olson <kc5gym@xxxxxxx>]

Paul McGlen wrote:
> Hi All,
>  
> I am using two 40 Amp variacs, one to limit the current and one as voltage control. I have wired them up as follows: The current control variac is in series with the input of the voltage variac (this variac has been cut to act as a variable inductor, 0.4 to 27.8mH) and the other end of the voltage variac is connected to the neutral; the brush is the output to my transformer. The problem is that when I turn on the mains, the voltage variac makes a buzzing sound (obviously mains frequency) and the ammeter is reading 10 Amps. I think that the core is saturating. However, if I remove the current control variac and connect the input of the voltage variac to another variac controlled power supply, so that the input to the variac in question is supplied via the brush output of the power supply variac there is only a quiet hum from the variac and the ammeter is reading about 0.5 Amps. What is wrong and how do I fix the problem?
>  
>  
> Thanks
>  
> Afrodita.
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>   
I am just a little unclear on what you are doing, but if the variacs are 
in series, and you are saturating the cores, then wind a reactance (with 
a laminated core, maybe one that can be adjusted in and out) to limit 
the current in the circuit.  Just my two cents.
p.s. maybe the reactance should be series too, or just across the 
current variac.

Marko
kc5gym@xxxxxxx

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