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Jabiru electric circuit design, your comments??

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matronics(at)rtist.nl
Guest

Posted: Wed Oct 20, 2010 6:24 am Post subject: Jabiru electric circuit design, your comments??

As winter sets in I am planning to rewire (some of) my plane. After studying

some of the aeroelectric diagrams and making a list of requirements I have

designed an electric system that I think should be easy to operate and safe.

You can find a copy here: http://www.rtist.nl/Files/JabPower.doc



The document only describes the main power circuit and protection setup.

nothing fancy with cross-feeds, alternate busses or anything yet. I'd like

to hear comments and concerns, if any...



Rob

mhubel

Joined: 05 Sep 2009
Posts: 141

Posted: Wed Oct 20, 2010 10:24 am Post subject: Jabiru electric circuit design, your comments??

Rob,

     While some of these things may be over kill, most do no harm and 

may be good. One thing to keep in mind is that most relays (contractors) 

that can also handle the full starting current have a continuous current 

draw of about one amp. With only 20 amps available in a 3300 

installation, this is significant. The risk of a starter relay getting 

stuck on is very low and essentially zero while in flight.

     One other thing to always consider, is that by adding complexity, 

is one trading one reliability problem for another. For example, Large 

caps are not the most reliable things in the world. By rights the cap 

should be fused. then the added resistance of the fuse reduces the 

effect of the cap. It is hard to win!



On 10/20/2010 10:18 AM, Rob Turk wrote:

 	  Quote: 	
		   



 As winter sets in I am planning to rewire (some of) my plane. After 

 studying

 some of the aeroelectric diagrams and making a list of requirements I 

 have

 designed an electric system that I think should be easy to operate and 

 safe.

 You can find a copy here: http://www.rtist.nl/Files/JabPower.doc



 The document only describes the main power circuit and protection setup.

 nothing fancy with cross-feeds, alternate busses or anything yet. I'd 

 like

 to hear comments and concerns, if any...



 Rob


	


-- 

Mark Hubelbank

NorthEast Monitoring

2 Clock Tower Place

Suite 555

Maynard, MA, 01754 - USA

mhubel(at)nemon.com

978-443-3955

_________________
Mark Hubelbank
N708HU
CH601XL
Jabiru 3300
Rotec TBI 40-3 carb
Sensenich ground adj prop.
240 hr TAF
Pictures at photo.hubbles.com

matronics(at)rtist.nl
Guest

Posted: Wed Oct 20, 2010 11:51 am Post subject: Jabiru electric circuit design, your comments??

Hmmm. It seems some people can't see the actual drawing. Here's a link to 

the JPEG image.

http://www.rtist.nl/Files/JabPower.JPG

---

craig(at)craigandjean.com
Guest

Posted: Wed Oct 20, 2010 12:39 pm Post subject: Jabiru electric circuit design, your comments??

One solution to the coil current on contactors is a manual switch. Del City

has some that are rated for 180 amps. But that leaves high current line in

the cockpit. One idea would be to remotely actuate it with a rod:



http://www.delcity.net/store/180A-Master-Disconnecting-Switch/p_4877.a_1



-- Craig

matronics(at)rtist.nl
Guest

Posted: Wed Oct 20, 2010 1:01 pm Post subject: Jabiru electric circuit design, your comments??

Mark,



Thanks for your comments, very welcome indeed.

I am aware of the contactor current. The main contactor draws about 1A. I 

think that's acceptable and a necessary evil. The alternator relay is a bit 

less power-hungry. I am planning to use an automotive relay which draws 

about 250mA and is rated for 40A.



You bring up a good point about the capacitor. I have one in right now and I 

have deliberately selected the one with the best lifetime and largest 

temperature range I could find. Not sure if the failure modes for this 

capacitor warrant adding a fuse to the circuit. I use one of these:

http://nl.farnell.com/epcos/b41560a7479m/capacitor-47000uf-40v/dp/4704903



The 'stuck starter' is a bit of a religious fight. My current setup has the 

starter contactor directly attached to the battery, and it works just fine. 

I agree with you that the chances of failure are very low, and essentially 

zero in flight. But the local engineer responsible for signing off cringed 

when I showed it to him, and he insists that there have been accidents and 

even fires from stuck starter contactors. Old wives tail? Who knows. If a 

simple rewire can avoid it, then I see no harm in making the modification.



 	  Quote: 	
		  From an operation point of view I don't consider this to be a complex 

system.
	


- Main switch disconnects everything.

- Starter can only be engaged if main bus has power.

- Alternator switch should be engaged to charge battery and run the 

electrics.

- Warning light reminds you to engage alternator.

- If alternator or regulator fail and cause high voltage, the OV module will 

cause a short through the alternator switch/breaker which trips at > 2 Amps.

- Warning light comes on when OV has tripped the alternator switch

- Current and voltage are monitored on dual Westach instrument.



Rob



---

matronics(at)rtist.nl
Guest

Posted: Wed Oct 20, 2010 1:02 pm Post subject: Jabiru electric circuit design, your comments??

Good suggestion, thanks!



---

flyadive(at)gmail.com
Guest

Posted: Wed Oct 20, 2010 2:09 pm Post subject: Jabiru electric circuit design, your comments??

Rob: 



How is the alternator mechanical driven?

If it is belt driven  - Go with a automotive alternator with a built in Voltage Regulator  - And you will have:

1 - Your crowbar circuit.

 2 - elimination of the alternator contactor

3 - Elimination of the Jabriu Voltage Regulator and all that extra STUFF.

And don't forget about the TIME and WIRING

For an alternator warning light a Voltage Comparator and LED will give you the warning.

 And it can be made to show when the battery is being charged.

-----------------------------------------------------------------------------------

Now if you cannot go with the automotive alternator my next question is:

 Why the Alternator Contactor?

The Output of the Alternator can be tied DIRECTLY to the Battery Buss.

The circuit you have ADDS RESISTANCE and TWO (2) failure points:

 1 - The Battery Contactor. INPUT & OUTPUT and 

2 - Contactor coil and Wiring harness.



Some may say that is four (4) failure points.

I'm guessing that your Ammeter is a Zero Center movement?

 If so, the deflection will be 0 to 30 Amps in either direction. <-- I would go slightly higher because Nominal output is 30 Amps, you have no surge leeway.

IS IT A 30 Amp Alternator?

Is the meter Analog or Digital?

 If Analog the sensitivity to LOW current draws will be poor if not nil.

If Digital check on the response of it.

I have always found a good SIMPLE volt meter is much better than an Ammeter.

 Small current discharges don't show up.

You will see it with your volt meter.

Your MASTER SWITCH:

I think you just did not put it in the schematic... But Use a Toggle Circuit Breaker (amperage to match the contactor), I'm guessing 5 Amps.

 



The R/C circuit for filtering Good Idea... But eliminate the resistor.

There is enough LOW resistance in the alternator handle bleed down.

And 47K uF is good.... 100K uF is even better.

 



Question:  What are pins 1, 3, 5 & 6 ?

Pin 6 LQQKs like Alternator output.  OK

The Alternator itself should be Grounded Also.

STARTER:

 Hang a LED off the OUTPUT of the Starter Contactor.

That way if the Contactor welds closed you will SEE the Lit LED and can shut the engine down.





OK, that's all for now.

 



Barry





  [quote][b]

DKennedy(at)scsd.us
Guest

Posted: Wed Oct 20, 2010 2:46 pm Post subject: Jabiru electric circuit design, your comments??

If it is   like  my  8cy   there is  no  belt   a  fixed  stators with  revolving  magnet  only on mine I have   double  stators   

From: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of FLYaDIVE

 Sent: Wednesday, October 20, 2010 6:07 PM

 To: jabiruengine-list(at)matronics.com

 Subject:  Re: Jabiru electric circuit design, your comments??

 Importance: Low  

Rob:     

How is the alternator mechanical driven?  

If it is belt driven  - Go with a automotive alternator with a built in Voltage Regulator  - And you will have:  

1 - Your crowbar circuit.  

2 - elimination of the alternator contactor  

3 - Elimination of the Jabriu Voltage Regulator and all that extra STUFF.  

And don't forget about the TIME and WIRING  

For an alternator warning light a Voltage Comparator and LED will give you the warning.  

And it can be made to show when the battery is being charged.  

-----------------------------------------------------------------------------------  

Now if you cannot go with the automotive alternator my next question is:  

Why the Alternator Contactor?  

The Output of the Alternator can be tied DIRECTLY to the Battery Buss.  

The circuit you have ADDS RESISTANCE and TWO (2) failure points:  

1 - The Battery Contactor. INPUT & OUTPUT and   

2 - Contactor coil and Wiring harness.  

Some may say that is four (4) failure points.  

I'm guessing that your Ammeter is a Zero Center movement?  

If so, the deflection will be 0 to 30 Amps in either direction. <-- I would go slightly higher because Nominal output is 30 Amps, you have no surge leeway.  

IS IT A 30 Amp Alternator?  

Is the meter Analog or Digital?  

If Analog the sensitivity to LOW current draws will be poor if not nil.  

If Digital check on the response of it.  

I have always found a good SIMPLE volt meter is much better than an Ammeter.  

Small current discharges don't show up.  

You will see it with your volt meter.  

Your MASTER SWITCH:  

I think you just did not put it in the schematic... But Use a Toggle Circuit Breaker (amperage to match the contactor), I'm guessing 5 Amps.  

The R/C circuit for filtering Good Idea... But eliminate the resistor.  

There is enough LOW resistance in the alternator handle bleed down.  

And 47K uF is good.... 100K uF is even better.  

Question:  What are pins 1, 3, 5 & 6 ?  

Pin 6 LQQKs like Alternator output.  OK  

The Alternator itself should be Grounded Also.  

STARTER:  

Hang a LED off the OUTPUT of the Starter Contactor.  

That way if the Contactor welds closed you will SEE the Lit LED and can shut the engine down.  

OK, that's all for now.  

Barry  

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matronics(at)rtist.nl
Guest

Posted: Thu Oct 21, 2010 2:05 am Post subject: Jabiru electric circuit design, your comments??

Hi Barry,

  

 Thanks again for all the feedback!

  

 The alternator is in fact the standard Jabiru 20A  single-phase generator/dynamo. Alternator is probably the wrong term here,  although Jabiru calls it a "Permanent Magnet Alternator". 

  

 Installing an automotive alternator would  require major mechanical modifications to run from the engine. With my  mechanical skills this would pose a much higher risk of failure than any of the  wiring  I have seen pictures of one person running such a setup and I'm not  up to the task to make such mods..

  

 The reason for running the generator/regulator  output through the relay is to enable overvoltage protection for COM, XPDR etc.  If the regulator fails (as it has in several documented cases) and spits  out high voltage, the OV crowbar would short-circuit the alternator contactor  relay. This short-circuit would make S2 (a combined switch/circuit braker rated  at 2A) trip, the relay would drop and the regulator output would be  disconnected from the bus. There are no other power sources that can deliver  more than 14V, so OV protection after that would not be an issue.

  

 The amp meter is indeed zero center. I am  using a combined analog V/A instrument (Westach 1022DA10-21). Max regulator  output is 20A, and max load is roughly the same. Under normal circumstances  nothing over 30A should ever occur.

  

 The master switch is in the schematics, it's S1. It  serves to activate the battery contactor as well as the alternator relay (when  S2 is also engaged). Making it a circuit breaker would protect against shorts in  the contactor coil, not sure how likely that is. But worth  considering.

  

 I am not sure the regulator will bleed the  remaining charge in the capacitor quick enough. The Jabiru regulator schematics  show the output to be a switched rectifier bridge with diodes and thyristors.  The diodes are in reverse and would block any bleed current, hence the resistor.  With this resistor it would still take about 30 seconds to bleed to half the  voltage. Taking the cowl top off takes about two minutes, so any accidental  short after that should be harmless.

  

 The regulator pins are defined in the Jabiru  manual. 1 and 3 are AC in. 2 and case are ground. 4 is low voltage warning  light. 5 is DC sense feedback. 6 is regulated DC output. I will add the ground  to the regulator case in the diagram.

  

 Good point on the starter indicator, will add that  to the diagram as well.

  

 Great discussion, thanks!

  

 Rob

 [quote]   ---

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Fri Oct 29, 2010 5:10 pm Post subject: Re: Jabiru electric circuit design, your comments??

I don't wish to over-analyze your schematic, however there are some features that need clarity;

The alternator contactor, rel.3  does not disconnect the AC from the regulator.

If the alternator contactor is open, depending upon the DC bus voltage at the time, the voltage applied to your capacitor will be more than 40 Volts, and it might not do nice things to your equipment when the contacts close.

Jabiru manual states the regulator output and sense wires should be tied together at all times, to prevent this possibility.



Think what might happen if you open the master switch, and the main contactor is open, and there is more than 6 volts difference between the batt volts and the DC bus volts. Will Rel.3 coil be energised via rel.1 coil and the battery connection? do you want this to happen?



The placement of the OVM crowbar module does not look appropriate to me.



I prefer either of 2 published wiring systems;  the Jabiru way or the Aerolectric way,  both are acceptable practice for homebuilt aircraft, its when a hybrid system is attempted that unexpected consequences could result.



Ralph

_________________
Ralph - CH701 / 2200a

matronics(at)rtist.nl
Guest

Posted: Fri Oct 29, 2010 11:51 pm Post subject: Jabiru electric circuit design, your comments??

Hi Ralph,



Thanks for your analysis. I think you have a point with the regulator 

sense wire, except Jabiru do not seem to practice what they preach. 

Looking at their schematics for the J160 Certified (3300 Installation 

Manual JEM3302-4) they have the regulator output direct to the battery, 

but the sense wire goes to the main bus bar, behind a 15A fuse and a 

toggle switch. Essentially the same as I do, except I use a battery 

contactor instead of a toggle switch.



One thing I do not know is what the regulator output will do when it's 

disconnected. It may go to full output as you suggest, or it may go to 

zero. The capacitor is rated at 40V, so even a full output situation 

should not cause any issues. Perhaps I should use a double-pole 

alternator relay and disconnect one of the A/C wires as well.



As for the OVM crowbar, it is connected directly across the alternator 

relay. Its placement is such that when the alternator circuit is 

connected, the OVM senses the power across main bus and (through S1 and 

S2) ground. If S1 or S2 opens, the alternator relay will open as well. 

If an over-voltage occurs, the OVM crowbar will short-circuit. This will 

open S2 (automatic circuit breaker) and disconnect the alternator 

circuit. This is exactly what AeroElectric does. Once the alternator 

relay is open, there are no other sources that can elevate the voltage 

above the battery level.



I'd appreciate your suggestions for a better placement of the OVM.



Rob



On 10/30/2010 3:10 AM, jetboy wrote:

 	  Quote: 	
		   



 I don't wish to over-analyze your schematic, however there are some features that need clarity;

 The alternator contactor, rel.3  does not disconnect the AC from the regulator.

 If the alternator contactor is open, depending upon the DC bus voltage at the time, the voltage applied to your capacitor will be more than 40 Volts, and it might not do nice things to your equipment when the contacts close.

 Jabiru manual states the regulator output and sense wires should be tied together at all times, to prevent this possibility.



 Think what might happen if you open the master switch, and the main contactor is open, and there is more than 6 volts difference between the batt volts and the DC bus volts. Will Rel.3 coil be energised via rel.1 coil and the battery connection? do you want this to happen?



 The placement of the OVM crowbar module does not look appropriate to me.



 I prefer either of 2 published wiring systems;  the Jabiru way or the Aerolectric way,  both are acceptable practice for homebuilt aircraft, its when a hybrid system is attempted that unexpected consequences could result.



 Ralph



 --------

 Ralph - CH701 / 2200a





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=317448#317448

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Sat Oct 30, 2010 11:15 pm Post subject: Re: Jabiru electric circuit design, your comments??

Rob



your placement of the OVM is not the same as Z20 or Z21 because you have changed the way S1 (S1 and S2 in your diagram) are wired. I cannot offer a different method as I don't use the OVM but if you are using one it would be safer to stick with the proven design as I found in your diagram the alternate path available through the master contactor coil which does not exist in Bob's designs and there may be other scenarios I have not noticed.



Note the regulator sense and output wires also tied together, yes I agree Jabiru airframes disobey their installation instructions for the engine and the airframes also disregard AC-43 wiring rules such as the use of aluminium bus bars clamped with AN hardware via fibreglass without spring washers or aluminium packing washers - this is a problem waiting to happen both from corrosion and joint loosening point of view so please check this area frequently.



Ralph

_________________
Ralph - CH701 / 2200a

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