Fixing a PWM DCC Fan Controller
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
mrvette
i think that's what baskin is talking about. when you turn the ingnition on, voltage is applied to the field coil in the alternator. but when it starts to spin there is a short (1/2 cycle?) delay in the feedback from the alt output to reduce the field coil votage. it's during this very short time that the output voltage at the bat terminal could spike. that's where baskin's idea of inductance of the wires (voltage leads current in inductance) throwing the current and votage out of phase comes from. that's why a capacitor is used to "tune" the circuit, because current leads voltage in capacitance. at least i think that's what he means?
jeff
i think that's what baskin is talking about. when you turn the ingnition on, voltage is applied to the field coil in the alternator. but when it starts to spin there is a short (1/2 cycle?) delay in the feedback from the alt output to reduce the field coil votage. it's during this very short time that the output voltage at the bat terminal could spike. that's where baskin's idea of inductance of the wires (voltage leads current in inductance) throwing the current and votage out of phase comes from. that's why a capacitor is used to "tune" the circuit, because current leads voltage in capacitance. at least i think that's what he means?
jeff
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
mrvette
i think that's what baskin is talking about. when you turn the ingnition on, voltage is applied to the field coil in the alternator. but when it starts to spin there is a short (1/2 cycle?) delay in the feedback from the alt output to reduce the field coil votage. it's during this very short time that the output voltage at the bat terminal could spike. that's where baskin's idea of inductance of the wires (voltage leads current in inductance) throwing the current and votage out of phase comes from. that's why a capacitor is used to "tune" the circuit, because current leads voltage in capacitance. at least i think that's what he means?
jeff
i think that's what baskin is talking about. when you turn the ingnition on, voltage is applied to the field coil in the alternator. but when it starts to spin there is a short (1/2 cycle?) delay in the feedback from the alt output to reduce the field coil votage. it's during this very short time that the output voltage at the bat terminal could spike. that's where baskin's idea of inductance of the wires (voltage leads current in inductance) throwing the current and votage out of phase comes from. that's why a capacitor is used to "tune" the circuit, because current leads voltage in capacitance. at least i think that's what he means?
jeff
IF I was to agree with the above, the whole theory of the one wire alt is kinda damaged, which as we know they will work fine, IF the alt is spun high enough like on a boat....I had one long time ago, worked fine old 10SI .....there is a cap internal to the alts, I remember that, but not where it's wired....seems to go across the main diode stack output heatsink, insulated from alt frame, as I recall....got a 2' thick pile of docs on this car, hard to find the exact diagram I need, of course...
at any rate, I fail to see how any voltage spike can happen at the output BAT stud on the alt....
