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John T Elec. En
04-19-2000 19:01:20
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Hey all my good friends I take a day off and miss out on a good electrical question. Regarding coil polartiy, most is true below, but some is NOT. First, If the tractor is say positive ground, then the spark plug current still flows the same direction REGARDLESS of how you wire the darn coil right OR wrong. The low voltage high current through the primary side of the coil still flows from the battery to the tractors frame via the contact points in the distributor, REGARDLESS of how you connect the coil. What it is though, if you hook the coil wrong, the current still flows BUT in the WRONG direction THROUGH the coil, although the polarity of the voltage drop across the coil is still the same. Its a series load and remains a series load voltage drop, regardless of how you wire the darn coil (its a passive device only), the current flow is determined by the battery polarity and NOT how you connect the simple series load coil, whether right or wrong. So now you ask why must it be wired as designed for ??? OK here is why. It was well and correctly stated below (good going buckeye man) a coil is indeed an auto step up transformer with both sides of high and low voltage windings common at the + side on the coil. But, a transformer works because current flow in a wire creates a magnetic field in its vicinity BUT that fields polarity (like N and S in a bar magnet) is determined by the direction of electron flow. AND the mutual inductance and transformer action between the coils primary and secondary windings was designed and wound in such a physical direction so as to enhance the mutual inductance to maximize it (if wired correct) and not be fighting and bucking and cancelling it out like buckeye there was referring to. So, if the coil is wired wrong, the curerent still flows through (but in wrong coil direction) it and the voltage drop polarities are the same, regardless how you wire it (passive load only its not an active device remember) but, if its wired as designed for, the mutual inductive coupling and transformer action is way more efficient and you develop more potential spark gap energy (then if wired wrong) across the plug gap as opposed to more of a heat loss in the coil due to inefficiencies by non proper oriented magnetic fields as when the curent flow is back asswards if its wired wrong. Thats my story and Im stickin to it. Hope this helps good safe fun tractoring to you all. PS1 Regardless of the super hype claims about how high a voltage some super coil is, the voltgae acros the coils high voltage secondary only rises to high enough to arc jump the plug gap distance only, and NO higher. Its the plug gap and material in the gap that determines the firing voltage. High energy elec ignitions are superior because you can run a wider plug gap (requiring higer voltage to arc across) and you also develop more current and arc energy and arc surface area and heat to better ignite the fuel. PS2 DC Welders are better for like overhead welding because electrons have a mass and in DC wedling they flow the same direction all the time and ur throwing electrons with mass up and toward the metal which helps the molten metal arc weld adhere better overhead especially. Ol John T Electrical Engineer and Country Lawyer.
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