effect of high current draw on charging system
effect of high current draw on charging system
(OP)
When a accessory like a dc/dc converter or inverter with 30A output is used that has a current draw (for milli/microseconds) that is higher than the alternator output rating , what is likely to be the effect?
A good diagram to keep us all on the same line of thought is
pp7 fig. 5-07 of
http://www.autoshop101.com/forms/elec05.pdf
What response time does the alternator's voltage regulator typically have? I've gone to alternator OEM websites, their .pdf datasheets are sales oriented, no internal technical specs are included.
If the typical small alternator w 60A rating has 120A or even 300A drawn for 1 ms, it appears to me that until the alternator's voltage regulator reacts, current could be drawn directly from the battery, which has an internal impedance, so the batteries Vout would drop.
Then, when the high current draw pulse ended, the alternator's rotor field would be set to deliver higher current, which would then be dumped on the bus, similar to load dump.
http://en.wikipedia.org/wiki/Load_dump
Having a load dump like event happen thousands of times per second does not sound like a good way to get normal longevity of the charging system.
Any of my estimations sound accurate?
Thanks for your input,
Paul
A good diagram to keep us all on the same line of thought is
pp7 fig. 5-07 of
http://www.autoshop101.com/forms/elec05.pdf
What response time does the alternator's voltage regulator typically have? I've gone to alternator OEM websites, their .pdf datasheets are sales oriented, no internal technical specs are included.
If the typical small alternator w 60A rating has 120A or even 300A drawn for 1 ms, it appears to me that until the alternator's voltage regulator reacts, current could be drawn directly from the battery, which has an internal impedance, so the batteries Vout would drop.
Then, when the high current draw pulse ended, the alternator's rotor field would be set to deliver higher current, which would then be dumped on the bus, similar to load dump.
http://en.wikipedia.org/wiki/Load_dump
Having a load dump like event happen thousands of times per second does not sound like a good way to get normal longevity of the charging system.
Any of my estimations sound accurate?
Thanks for your input,
Paul





RE: effect of high current draw on charging system
"thousands of times per second does not sound like a good way to get normal longevity of the charging system.
Any of my estimations sound accurate?
"
That one sounds goofy, for a start.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: effect of high current draw on charging system
My main concern is whether repeated overcurrents have a small but cumulative damage to any of the charging system.
Anybody out there ever done any load dump simulating or alternator reliability testing?
Thanks,
Paul
RE: effect of high current draw on charging system
If the current is to high for to long, or to frequent wit insufficient recovery time, it will overheat the windings, but that takes a little while and is very dependant ant how long and how much current vs cool down time.
Regards
Pat
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RE: effect of high current draw on charging system