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  #81  
Old 10-19-2017, 07:46 PM
rv7charlie rv7charlie is online now
 
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To save Dan a little time, look at page 9 of the PPS installation manual. There's no control over the field lead provided by the PPS.
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  #82  
Old 10-19-2017, 08:08 PM
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cjensen cjensen is offline
 
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The PPS does not have ability to shut off the alternator, it is simply a solid state contactor/solenoid system. The VP-X provides over-voltage protection, the PPS does not.
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  #83  
Old 10-20-2017, 06:50 AM
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Quote:
Originally Posted by cjensen View Post
The PPS does not have ability to shut off the alternator, it is simply a solid state contactor/solenoid system. The VP-X provides over-voltage protection, the PPS does not.
Chad, can you supply some details about the VPX OV protection? I suspect a lot of VPX purchasers are early adopters, and thus more likely to also install an EarthX or similar...even when they don't understand any of it.

From the VPX installation manual:

Over-voltage protection is provided by removing power from the Field wire when the bus voltage exceeds a pre-set limit for a pre-set period of time.

The voltage trip limit for a 12v system is intended to be 16v like other OV systems (see note below). What is the pre-set time period before disconnection of the field lead?

In reviewing the manual, I note that users are expected to configure the trip point for 12v or 24v systems. If a user fails to configure a 12v system properly (sets for a 24v system), the OV protection will be useless with some LFP batteries and they will smoke. An EarthX BMS should disconnect at 16v, so a misconfiguration should not be a problem. Regardless, perhaps this point should be made much more obvious to purchasers.

Quote:
Originally Posted by F1R View Post
I expect that an objective study and presentation of the speed of the various over voltage devices will soon be in order. A friend had an OV event in his RV 10 that nuked both his AFS displays internal OV protection along with other avionics. The VP-X was not fast enough to prevent that. Had it been in solid IMC he had zero flight instruments remaining.
The RV 10 had SLA batteries, with an internally regulated auto alternator.
Is your OV protection fast enough?
Pretty good example of a user not understanding the system. The user apparently connected the VPX to an auto alternator that, once running, could not be shut down by disconnecting its field wire. If that's not the case (the alternator design would in fact halt output with a field disconnect), then the VPX had an issue.

Here's a question...we know Plane Power and B&C (with B&C regulator) have OV protection, and the VPX can open the field on either, which effectively doubles the OV protection. Are there any other alternators in the marketplace which can be shut down by opening the field lead?
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Last edited by DanH : 10-20-2017 at 07:26 AM.
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  #84  
Old 10-20-2017, 07:17 AM
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cjensen cjensen is offline
 
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The VP-X OV protection on a 12v system is set at 15.9, and 31.9 on a 24v system. I don't know the timing, but I will find out...milliseconds though.

I agree with you on the info in the manual needing to be more obvious with better technology batteries available now, I will take that as an action item for immediate revision.

I'll get the timing info as soon as I can. I am out of the office today, but if I'll shoot an email to engineering before I leave the house today.
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  #85  
Old 10-20-2017, 07:23 AM
rv7charlie rv7charlie is online now
 
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Dan,

In the interest of using precise terms, I don't think we should call that terminal on internally regulated alternators a 'field' terminal. In the IR alternators I'm familiar with, it doesn't connect to the field; that's why it won't control the alternator after startup. If memory serves, it's actually a control input that tells the regulator to turn on. And in alternators with that particular style regulator, the regulator, once told to turn on, will 'latch' on & the latch won't drop until the alternator stops spinning (making power).

Calling it a 'field terminal' can give the (wrong) impression that an alternator can continue to produce power without the field winding connected.
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  #86  
Old 10-20-2017, 07:31 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by rv7charlie View Post
Dan,

In the interest of using precise terms, I don't think we should call that terminal on internally regulated alternators a 'field' terminal. In the IR alternators I'm familiar with, it doesn't connect to the field; that's why it won't control the alternator after startup. If memory serves, it's actually a control input that tells the regulator to turn on. And in alternators with that particular style regulator, the regulator, once told to turn on, will 'latch' on & the latch won't drop until the alternator stops spinning (making power).

Calling it a 'field terminal' can give the (wrong) impression that an alternator can continue to produce power without the field winding connected.
In the IR alternators I use, pulling power off the field terminal certainly stops the alternator from charging.
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  #87  
Old 10-20-2017, 07:32 AM
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Bill Boyd Bill Boyd is offline
 
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Default From my experience

Quote:
Originally Posted by DanH View Post
Chad, can you supply some details about the VPX OV protection? I suspect a lot of VPX purchasers are early adopters, and thus more likely to also install an EarthX or similar...even when they don't understand any of it.

From the VPX installation manual:

Over-voltage protection is provided by removing power from the Field wire when the bus voltage exceeds a pre-set limit for a pre-set period of time.

The voltage trip limit for a 12v system is intended to be 16v like other OV systems (see note below). What is the pre-set time period before disconnection of the field lead?

In reviewing the manual, I note that users are expected to configure the trip point for 12v or 24v systems. If a user fails to configure a 12v system properly (sets for a 24v system), the OV protection will be useless with some LFP batteries and they will smoke. An EarthX BMS should disconnect at 16v, so a misconfiguration should not be a problem. Regardless, perhaps this point should be made much more obvious to purchasers.



Pretty good example of a user not understanding the system. The user apparently connected the VPX to an auto alternator that, once running, could not be shut down by disconnecting its field wire. If that's not the case (the alternator design would in fact halt output with a field disconnect), then the VPX had an issue.

Here's a question...we know Plane Power and B&C (with B&C regulator) have OV protection, and the VPX can open the field on either, which effectively doubles the OV protection. Are there any other alternators in the marketplace which can be shut down by opening the field lead?
The Denso 14824 is controllable thusly. I was able to turn it on and off several times under load when the regulator or associated wiring failed in flight and produced a 36v OV event. This was before I rewired my ship to have a crowbar and a B-lead contactor controlled by same. The "field" terminal did in fact control the alternator's on-off state.
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  #88  
Old 10-20-2017, 09:28 AM
rv8ch rv8ch is online now
 
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Default alternator control

I've tested internally regulated alternators and they do turn off and on with the "control" wire under normal circumstances. The question that I've read posed by those much more expert on this than I am is "will the alternator turn off if there is a failure of the internal regulator?"

There is a risk that they will not turn off, so Bob Nuckolls has proposed this solution, which seems quite solid.



The tricky part is to find the TVS device - I bought one from Eric, but he does not sell them any more for some reason. (http://www.periheliondesign.com/)
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  #89  
Old 10-20-2017, 09:53 AM
Kalibr Kalibr is offline
 
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What about the "interim" figure Z-24 solution from the Bob Nuckolls book?
I understand that the only issue with that approach is that some internally regulated alternators may get fried if they are "turned off" by disconnecting the B lead. Which I wouldn't mind as much as I'd expect it to happen in a situation where the alternator would need to be replaced anyway. Plus, we would be talking about a less than a $100 automotive alternator and not the $$$$$ "aviation" model.
What am I missing?
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  #90  
Old 10-20-2017, 10:23 AM
rv7charlie rv7charlie is online now
 
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Mickey, are you sure that schematic was for a full blown OV event, or for surge mitigation? Doesn't look very 'Bob-like', since the TVS would be required to take the full current of the OV event until the alt dies completely, or the flight ends.

I share the concern about expecting an internal regulator that has failed, causing an OV event, to then provide the protection from itself.

Kalibr, IIRC, the reason Bob pulled the drawing was that builders were combining it with an alternator control switch, and flipping the switch off in flight, killing the alternator due to 'load dump'. If you use the circuit, and treat the system like the ones in cars (alt always on), it works fine, with positive control of OV events. And you can't kill an alt that's already dead. :-)

Charlie
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