effect of high current draw on charging system 2

[pt321]

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

 

[GregLocock]

Why not measure the battery voltage when you switch your DC inverter on? Then you could answer your own question.

"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

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[pt321]

Greg: thanks for considerations. I expect the battery voltage would have a slight drop during overcurrent, but my business partner has the scope for a while, it'll be a while before I can check on a secondary concern like the batter output.

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

 

[patprimmer]

If a voltage spike is to high it will blow a diode or the regulator.

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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[LionelHutz]

I'd bet money the inverter has input filtering so it applies close to a steady load on the electrical system.