If diodes are located away from *, then [i] air cooling of * will work better ; no obstacle exist @ end of alternator to block air flow pushed through * by impeller [ii] given these diodes produce 1 - 1=BD v of voltage drop ( per
formatting link
so a 80 amp output will produce 80 - 120 w of heat which ( if cooled by heatsinks ) will not flow into * & reduce ampere output, or toward & into battery.
I use an aluminium dish, copper bolt, old wires & heatsinks to cool my Denso alternator, & found cooling produces more amps & voltage esp when engine idles @ just 550 rpm, exactly as per
formatting link
where I learnt that the cooler is alternator, the more amps are produced.
I suspect the main reason is for electrical interference reasons. Long wires from the stator carrying high frequency AC will act like an antenna and broadcast noise that the radio can pick up. The other issue is that more wires and connectors are necessary.
My alternators are internally rectified and regulated making a nice one piece unit, it's convenient.
If diodes are away from alternator, you have to cool them separately. That means larger heat sink (that can get fouled with dirt/bugs under the hood) or perhaps some other ducted air flow.
The extra energy you get from running the alternator without the diodes in the air stream has got to be pretty small. Compare with cost of extra wiring to diodes located some distance away, the possible need for EMI shielding, the separate, much larger heat sink needed. I'm sure the most economical package is the one commonly seen with the diodes built into the alternator case.
The main reason the diodes are best kept grouped as closely together as possible and as close to the source energy as possible are for electrical efficiency. The heatsink paths are also conduction paths. Alternators with remotely placed diode strings are far less efficient, just from wire/connectivity issues standpoint alone.
The same heatsink if located away from * will disperse more heat ; better air flow.
This design is good for a cold climate, heat from diodes & * will flow into engine & battery ( ideal temperature is 80=BAF or =BA26.7=BAC
formatting link
, so heat from diodes will not heat battery to >
26.7=BAC ). In a hot climate, heat is bad for engine ( ideal coolant tmprtre for e.g. honda is just 78=BAC ) & battery, so if diodes have a heatsink & are away from stator, both engine & battery will be less hot. In just 33=BAC air, my Denso alternator was too hot : during idling @
550 rpm & feeding so many loads, produced just 12.1 v ( could not even charge battery ), heat flowed toward fuse box & into battery during long trips, battery then self-discharged & drew more & more amps from diodes ( so sparks got smaller & smaller ). Only after I ( spent >10 hr ) added cooling to alternator, & used 8 small ( 5 amp ) wires ( 1.3 ft long, 8 in parallel ) & 2 lugs to connect ( in series ) to diodes & output wire, could I stop this heat flow to fuse box ( main terminals were too hot to touch ! ) & battery. I think an alternator for a hot climate should have [i] big impeller [ii] diodes away from * [iii] heatsink on diodes, & fins ( like air cooled engines' ) on alternator [iv] e.g. 8 smaller ( instead of 1 big ) output wires to disperse heat flowing toward battery. I want to but Google does not let me post any photo of my alternator with hsinks & wires, & this NG rejects any post direct from Msia.
No the heat sink placed far away from the alternator would not have any air flow. Unless you rig up a separate fan for it. That's the point of installing the heat sink in the alternator's air stream. The air flow cools two components with one fan.
Now you're running conductors much farther from alternator/engine/battery. Now you definitely need an auxilary fan for the diode heat sink. Now you've definitely spent more money on components than you'll ever save in energy.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.