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"jon s kowitz" <jonskowitz-at-hotmail.com>
Re: Prof. Sommer's Controller Review [TANKS]
Wed, 06 Apr 2005 04:18:10 +0000
>Technical digression about "just a couple pieces of metal
>being pulled together" -
>24V causes significantly more arcing than 12V when
>contacts make and break. Inspecting the "Load
>Limit Curve" graph on the Tyco/P&B spec sheet
>shows that the arc will always extinguish for 12V
>across the contacts (Load limit curve 1). For
>24V across the contacts, the arc may not completely
>extinguish during transit time for loads above 7A.
>24V will not cause stationary arcs (Load limit curve 2).
>Stationary arcs are VERY bad.
You can use capaciters to reduce or even eliminate arcing across the
contacts by increasing the time it takes for the circut to turn "off" after
the contacts are opened. Not sure how much capacitance you would need for
how much motor though. A good capaciter to try might be the condenser from
an old points style automotive ignition system. NAPA should carry them for
a reasonable price.