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Re: Placement of Ballast Resistor
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Posted by Bob M on January 15, 2006 at 09:09:42 from (69.205.118.76):
In Reply to: Placement of Ballast Resistor posted by Thomas Donahy on January 15, 2006 at 07:27:04:
Thomas - Your suspicion is correct: Placement of the ballast resistor has no effect on the primary circuit. A few thoughts: ---- 1 - The coil primary (12 volts DC) and coil secondary (spark voltage) are connected at only one point: Both are grounded to the coil shell. Otherwise they electrically independent. Consequently primary current can flow ONLY in the primary circuit and spark current can flow ONLY in the secondary. Ie. NO spark current flows through the primary ballast resistor. ---- 2 - That said, since the primary is a simple series circuit the ballast resistor can located at any point in the circuit. Between the ignition switch and the coil is the usual resistor location. (As you note, placing the resistor here makes it simple to bypass for starting.) However it can also go between the coil and the distributor, or (if there are no other loads fed off the ignition switch...) between the ammeter and the hot side of the ignition switch. ---- 3 - Ignition park occurs the instant the ignition points open - ie. when they break the primary ciruit. (The high voltage is induced in the secondary by the collapse of the magnetic field that exists when current is flowing in the primary winding). Also the condensor does not act as an open circuit - rather it absorbs the voltage spike as the points separate to reduce arcing at the points. ---- Hope this makes sense!
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