Ebus question

[sonny junell]

I am purchasing a SD20 "aux alternator" and after reviewing ?Bob Knuckles Aerolectric Connection Z12 it appears he recommends I connect the field connection to Main power Distribution Bus My question is why? It seems I would want this connection on the E-BUS. Could you direct me to where I could find more info on this

Thank you

[Walt]

The SD20 powers the main bus just like the "failed" main alternator did, only with less capacity than the orginal. The purpose of a BUG (back up gen) is to power the main main bus, the purpose of the ESS bus is when you are only running off the battery and want to conserve every possible amp you can for max endurance.

[sonny junell]

Thanks that make much more sense.

I was putting too much emphasis on the e-bus. . . . Maybe i will just have a straight on off master ? ? ? ?

this is the response i got from b&c "great guys" btw

Sonny,

Thank you for your inquiry.

The best I can only offer you is an interpretation of Bob's design goals in
Z-12, since it is his creation. Naturally, I would defer to him as the last
word on the subject.

My understanding is that the goal behind Z-12 was to preserve as much
flexibility as possible in the event of a major failure. With the SD20
positioned on the main bus, you retain the option of powering devices
normally located on that bus in the event of a primary alternator
failure...OR in the event of a master contactor (or battery) failure on the
main bus the diode in between the two buses would allow the SD-20 to supply
the needs of the e-bus. In other words, Z-12 as designed gives you a "Plan
B" to deal with either possibility.

I hope this is helpful. We appreciate your contacting us.

Kind Regards,

"TJ" Jenkins
B&C Specialty Products

[elippse]

I see that you have a fuse/CB in the line from the alternator output to the main buss, and the field is connected basically to the main buss. If the alternator CB opens up, the buss voltage will decrease. The regulator will then sense low voltage and supply maximum current to the alternator field. With no load on the alternator, its voltage will rise to over 100V. Then if you close-through the alternator CB, you'll put a large transient voltage on the main buss until the regulator and field current decay to the required output. This could take milliseconds, which is a long time in electrical terms. The solution to this is to connect the field from the alternator-side of its CB, so that it will stay in regulation and the field will serve as its load. 'Make sense?

[Walt]

Originally Posted by elippse

I see that you have a fuse/CB in the line from the alternator output to the main buss, and the field is connected basically to the main buss.

Actually I believe that is a current limiter/fuseable link, if it blows the alternator is on vacation until you replace it.