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VPX issue with BandC alternator

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Bavafa

Well Known Member
I am helping a friend to troubleshoot a problem with his newly purchased RV10 and I was wondering if anyone has seen this issue or knows what the cause is. His plane has two B&C alternators, a 60A for the main and a standby. The output of both go to the VPX and on the VPX there are two CB for the Alt Field, one for each, which are connected to a physical switch on the panel.
The first observation: Not both Alt field CB can stay closed at the same time. When we flip the main Alt field On, the CB for that goes green but as soon as the second Alt field switch is turned On, the first CB jumps as the second one goes green. This means a manual process is required if the active alternator goes dead. This however might be the normal operation as VPX manual indicates that only one PlanePower alternator can be in the ON position which may also be true for B&C.
The second issue which is more puzzling and rather critical: If/when the primary alternator is operational, if the main battery gets disconnected, then we get an overvoltage for the Alt field CB and gets tripped and all power to the ship is dead. The normal draw that we see for the CB is about 2.8A. This does not happen if the standby alternator is operational, removing the cable from the battery has no impact on the alternator operation.

This plane has an electronic ignition that is dependent on ships power, so the first scenario will cause the fan in the front to stop working, hence the criticality of the issue.


Any/All info is welcomed and appreciated.
 
Which voltage regulator are using? VPX warns that the SB1B can't be used.

Stein recommended to not connect either alternator to the VPX in an electrically dependent engine set-up, I complied.
 
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Just a guess, but is it easy to swap those identical regulators and see if the behavior follows them or stays wiith the respective alternators?

FWIW my (older generation) VPX also only energizes 1 field wire at a time it lets me pick which one with the switches assigned to the role. I have no alternators or voltage regulators yet (still building).

Good luck
 
Bavafa said:
I am helping a friend to troubleshoot a problem with his newly purchased RV10 and I was wondering if anyone has seen this issue or knows what the cause is. His plane has two B&C alternators, a 60A for the main and a standby. The output of both go to the VPX and on the VPX there are two CB for the Alt Field, one for each, which are connected to a physical switch on the panel.
The first observation: Not both Alt field CB can stay closed at the same time. When we flip the main Alt field On, the CB for that goes green but as soon as the second Alt field switch is turned On, the first CB jumps as the second one goes green. This means a manual process is required if the active alternator goes dead. This however might be the normal operation as VPX manual indicates that only one PlanePower alternator can be in the ON position which may also be true for B&C.
The second issue which is more puzzling and rather critical: If/when the primary alternator is operational, if the main battery gets disconnected, then we get an overvoltage for the Alt field CB and gets tripped and all power to the ship is dead. The normal draw that we see for the CB is about 2.8A. This does not happen if the standby alternator is operational, removing the cable from the battery has no impact on the alternator operation.

This plane has an electronic ignition that is dependent on ships power, so the first scenario will cause the fan in the front to stop working, hence the criticality of the issue.


Any/All info is welcomed and appreciated.
Click to expand...
When I installed my 2 B&C alternators, I set one of the B&C regulators 1/2 vdc lower so they don’t interact/interfere with each other. This was at the guidance of B&C. I don’t use a VPX but my config has never had an issue.
 
It is normal for the overvoltage circuit to activate if the battery is removed. Don’t do that. The battery should remain connected in order for the alternator and regulator to work properly.
 
vic syracuse said:
It is normal for the overvoltage circuit to activate if the battery is removed. Don’t do that. The battery should remain connected in order for the alternator and regulator to work properly.
Click to expand...
Vic,
I appreciate your input but do you know why it would do that especially that it doesn't do it with the standby alternator and my own RV14 doesn't do it which has a traditional CB. We replicated it multiple times and each time it remained ON with the standby alternator but not with the main alternator.
To explain why we are concerned and doing this troubleshooting is that the battery cable was loose and had caused an engine failure right before a take off which would have been disastrous given the airport location and environment. If this is a normal behavior, then it poses a serious shortcoming for an airplane/engine with EI that is electrically dependent to run.
 
vic syracuse said:
It is normal for the overvoltage circuit to activate if the battery is removed. Don’t do that. The battery should remain connected in order for the alternator and regulator to work properly.
Click to expand...
May I ask about the mechanism that causes this? My understanding (which may not be entirely correct) is that the battery's role is to absorb ripple and to re-excite the feild if needed?

Can having a small avionics backup battery being charged though a diode have a meaningful effect in what happens here?
 
I have 2 B&C alternators, both with their own LR3D-14 regulators.
They are both connected through VPX and I confirm that just one Alternator can operate at a time.

I had a similar issue when the Backup Alt was on, I would get an Over-voltage warning from Dynon. Volts would rise above 14,5 - 15 - 16 and if I didn't switch it off it would continue rising to 18+...
I tested everything, following B&C's troubleshooting guide, using a multi-meter everywhere, interchanging the Volt-Regs, everything tested OK...

My Backup Alt & Battery will only feed the EFII Bus manager and it's Main & Esssential Busses. My choice as I wanted to seperate both systems.
I found out finally that I mis-wired the Backup VR, as it was not informed of the Bus Voltage from the EFII Bus Manager.
One dedicated VPX pin was connected to the Backup VR Bus Voltage Sense Input but VPX sent it's own bus voltage, which was low because the Main Alternator was off.

So one new wire from the EFII Bus to the Backup VR Bus Voltage Sense (terminal #3) resolved the issue.

In summary, check that both VR's receive proper Volt sensing.

Hope that helps
 
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