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Re: Powerstat Surge
On Thu, 23 May 1996 21:57:14 -0600, Tesla List
<tesla-at-poodle.pupman-dot-com>, you wrote:
>
>We were discussing last week surge current blowing breakers and fuses when
>the power is switched on to the larger variacs. I was looking at my wiring
>last night and remembered the welder (and it's parallel resistors) are
>connected in series with the line going into the Powerstat. I would guess
>this acts as a load resistor and knocks the current spike down low enough not
>to take out my fuses or breakers.
>
>If I remember correctly, this was suggested to me by Richard Quick.
>
>Ed Sonderman
>
>[ I wonder if it matters what order things are in. I have the variacs first,
>and the arc welder between them and the pole pig. -- Chip ]
>
Chip,
Yes it does, remember a variac IS a coil of wire on a magnetic
core. If you shut off the power at (say) the positive peak voltage,
the core will remain magnetized. If the next time you connect the
variac, the mains power is the opposite polarity, you have in effect
connected the variac to 440V and the current for that half cycle will
be huge.
jim