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Wiring 3300 to an alternator switch
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BobsV35B(at)aol.com
Guest

Posted: Sun Mar 23, 2008 7:16 pm Post subject: Wiring 3300 to an alternator switch

Good Evening Ralph,

  

 In the paragraph below, what does OC stand for?

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

628 West  86th Street

Downers Grove, IL 60516

630 985-8502 

Stearman  N3977A

Brookeridge Air Park LL22

  

  In a message dated 3/23/2008 9:41:31 P.M. Central Daylight Time,  sanson.r(at)xtra.co.nz writes:

  	  Quote: 	
		  

The    series switching regulator, when up to full voltage on the DC bus, is OC, and    the AC available from the PMA is not consumed. The windings stay cool, and    there is no load on the engine because the magnets are passing a coil that is    not connected  anywhere.

	






Create a Home Theater Like the Pros. Watch the video on AOL Home.

  [quote][b]

Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Sun Mar 23, 2008 7:55 pm Post subject: Wiring 3300 to an alternator switch

Bob,  

Better to ask Ralph, he raised it.  

But it is a type of transistor like a triode it will conduct when the grid voltage reaches switching level usually set at 14.5V for this application. So a voltage sensing device triggers the SCR at 14.5V and it conducts excess current to earth.  

“I think”  

Peter   

         

  

From: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of BobsV35B(at)aol.com

 Sent: Monday, 24 March 2008 12:19 PM

 To: jabiruengine-list(at)matronics.com

 Subject: Re: JabiruEngine-List: Re: Wiring 3300 to an alternator switch  

  

     

Good Evening Peter,  

    

   

    

Just a bit of information if you will. What is an SCR?   

    

   

    

Happy Skies,

 

 Old Bob

 AKA

 Bob Siegfried

 Ancient Aviator

 628 West 86th Street

 Downers Grove, IL 60516

 630 985-8502 

 Stearman N3977A

 Brookeridge Air Park LL22    

   

      

In a message dated 3/23/2008 5:39:47 P.M. Central Daylight Time, peterjfharris(at)bigpond.com writes:  

   	  Quote: 	
		    

Newer motorcycles, Jabiru and i believe Rotax 912  use a series switching

 regulator. That is, when the transistors see the voltage applied to the

 yellow 'sense' wire is lower than the internally preset reference voltage,

 the bridge rectifier is triggered on. this is by activation of the two SCRs

 that are in the -ve legs of the bridge. The SCR that is conducting remains

 conducting until the end of the AC cycle coming from the stator windings, at

 this time the SCR remains non conducting unless there is a fresh trigger

 from the transistors that sense the voltage.  	
  

  

  



 

         

  

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Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Sun Mar 23, 2008 8:11 pm Post subject: Wiring 3300 to an alternator switch

In a message dated 03/23/2008 9:41:31 PM Central Daylight Time, sanson.r(at)xtra.co.nz writes:

  	  Quote: 	
		  Anytime the sense wire is not directly connected to the output, you need another form of protection, because the voltage control loop is open, and like an automotive alternator, full output will be made available to all in its path. 	


 Hi Ralph- obviously you have a pretty good handle on this stuff, so could you please shed some light on one aspect I'm confused on:  It is my understanding that in a PMA  when a magnet passes a coil, there is some maximum amount of current induced in the coil (load-dependant, of course), based on number of coil windings and power of the magnetic field provided by the magnet.  (Not sure how velocity of the passing magnetic field affects this)  This results in a maximum voltage value for the given magnet/coil/(velocity?) event, and that voltage would be self-limiting, or incapable of a "runaway", which is not the case in a typical automotive-type alternator supplied by a "regulated" voltage to a field winding as mentioned above.

  

 With a PMA regulated by the device shown in the Jabiru manual, when the SCRs are triggered to charge the system because the reference voltage set point was reached, wouldn't each charging event (peak sine wave voltage achieved as magnet passes a coil with SCRs gated on) reach the maximum possible voltage based on the above situation?

  

 (I understand how a large capacitor between the alternator leads would reduce the peak-to-peak voltage, I think...)

  

 Appreciate your input on this issue- great discussion!

  

 Mark



Create a Home Theater Like the Pros. Watch the video on AOL Home.

  [quote][b]

_________________
From The PossumWorks...

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Sun Mar 23, 2008 9:36 pm Post subject: Re: Wiring 3300 to an alternator switch

Mark,



A couple of terms - OC means "open circuit"  SCR is the abbreviation of "silicon controlled rectifier" and is a diode that will not conduct until a trigger signal is applied to the control lead, thereafter it remains conducting unless the current passing thru is all gone. This occurs when the PMA output voltage changes to the reverse polarity, as the voltage passes thru zero the SCR unlatches and remains off until another trigger voltage is applied to the gate.



The generation of voltage by the PMA is limited by the number of turns on the windings, and I think the velocity of the magnets moving past. the current draw available would be determined by the rpm and strength of the magnets I expect, and these conditions will mean it is self limiting. But to get it to operate satisfactorily at say 2,000 rpm the unit will end up producing more than those requirements at 3,300 rpm.



There is no need for regulating the maximum current because even shorting the windings doesnt produce much more. The voltage needs regulating for a large portion of the running especially at low loadings it will be 3 or 4 times the minimum requirement.



Your last question is correct - each time the SCRs are triggered in order to let thru some more charge, the remainder of that half cycle AC is output to the load. If the load is a capacitor or battery the current is stored as a charge and the voltage rises slightly. If there is no load connected, other than your $$$ avionics, then the half cycle pulse results in a substantial voltage peak. This all happens very quickly but in most cases the internal capacitors will store it. If the avionics meet DOD-160 they will be immune. We are only talking of the part of the cycle that is over the 14 volts so the duration of these pulses will be less than one thousandth of a second. Not every cycle will be triggered and not every trigger will result in an overvolt spike because there is no timing control applied to the triggers. It is a relatively robust  simple design for the purpose of charging the battery and running the lights and horn on your lawn tractor. I have measured the spikes and voltages on my 15 amp 2200a PMA and there is nothing to be concerned with. I use the PC925 26 AH battery which can accomodate most problems.



The most efficient way to do this would be to fully rectify the PMA and apply the 15 - 85 volts to a switchmode inverter with a steady 13.8 volt output. These are off the shelf items but as soon as you get a bit of moisture in will probably fail so would be better off fitting a regular 3 phase alternator/regulator. - and the OV protection.



Ralph



could you please shed some light on one aspect I'm confused on:  It is my understanding that in a PMA  when a magnet passes a coil, there is some maximum amount of current induced in the coil (load-dependant, of course), based on number of coil windings and power of the magnetic field provided by the magnet.  (Not sure how velocity of the passing magnetic field affects this)  This results in a maximum voltage value for the given magnet/coil/(velocity?) event, and that voltage would be self-limiting, or incapable of a "runaway", which is not the case in a typical automotive-type alternator supplied by a "regulated" voltage to a field winding as mentioned above.

  

 With a PMA regulated by the device shown in the Jabiru manual, when the SCRs are triggered to charge the system because the reference voltage set point was reached, wouldn't each charging event (peak sine wave voltage achieved as magnet passes a coil with SCRs gated on) reach the maximum possible voltage based on the above situation?

  

 (I understand how a large capacitor between the alternator leads would reduce the peak-to-peak voltage, I think...)

  

 Appreciate your input on this issue- great discussion!

  

 Mark



Create a Home Theater Like the Pros. Watch the video on AOL Home.

   	  Quote: 	
		  [b]

_________________
Ralph - CH701 / 2200a

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Mar 24, 2008 12:08 pm Post subject: Wiring 3300 to an alternator switch

Ralph:



Turns, Speed, strength of the magnets and I believe proximity of the

magnetic poles to the coils.



Noel

The generation of voltage by the PMA is limited by the number of turns on

the windings, and I think the velocity of the magnets moving past. the

current draw available would be determined by the rpm and strength of the

magnets I expect, and these conditions will mean it is self limiting. But to

get it to operate satisfactorily at say 2,000 rpm the unit will end up

producing more than those requirements at 3,300 rpm.

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

checkpoint2(at)comcast.ne
Guest

Posted: Mon Mar 24, 2008 1:12 pm Post subject: Wiring 3300 to an alternator switch

Any one, is there a known conversion for a belt driven or direct

drive

Alternator For the rear of a jabiru 2200 engine? Bob Haas Alpi Pioneer. 



--

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Mon Mar 24, 2008 8:14 pm Post subject: Wiring 3300 to an alternator switch

Ralph-

  

 Good stuff- nice SCR description.  I used these puppies for 25+years welding car bodies for GM, but still unqualified to understand overvoltage conditions in PMAs.  Referring to page 54 of January '08 version of Jabiru document 3300HL-IM JEM3304-4.pdf:

  

 http://www.usjabiru.com/images/pdf/manuals/new%20stuff/3300HL-IM.pdf

  

 which (somewhat miserably!) shows the regulator/rectifier circuit, it would seem the regulator is only offered one-half of the phase generated by the PMA, unless the SCRs provide the other half-cylce in some way I misunderstand.  I've stared at this drawing for some time and have been unable to devine its secrets. If you could please take some time to decipher its function, I (we?) would be greatly indebted!  

  

 For the sake of this discussion, let's call the transistors T1-T4, left to right. In my estimation, T1 is voltage reference controlling T4 based on zener value, which in turn controls T3 that gates the SCRs.  T2 turns on the charge lamp, which seems to illuminate lamp when circuit is charging, as opposed to when it is not(?!). Perhaps you can unravel this Gordian knot for this lesser electron herder.

  

 You also mention 15-85 volts available from the PMA- original concern was regarding overvoltage.  Are you saying that there is a potential (no pun intended!) for as much as 85 volts to the system which would normally be absorbed by the battery, and that battery disconnect with alternator running might develop into a "bad day"?

  

 Thanks again for your input!

  

 Mark



Create a Home Theater Like the Pros. Watch the video on AOL Home.

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From The PossumWorks...

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Tue Mar 25, 2008 1:47 am Post subject: Re: Wiring 3300 to an alternator switch

Mark,



That regulator cct diagram really is difficult to follow with the transistors drawn upside down etc. but after studying it for a few years I decided it should work. Both the sense transistors and the ouput do get full wave rectifiers - its just that 2 diodes of the bridge are used for both functions and each of the SCRs forming the remainder of the bridge just supply the output -ve return. I have not tried fitting the 'charge' lamp and in my plane it would give me flat battery anyway.



The 85 Volts or so is allways available from the PMA if unloaded however with this type of regulator its not likely to ever get thru to the output unless the sense wire has become disassociated with the output. it would not be as violent as an automotive field controlled alternator going full on however now that all engines are fitted with the 20 amp 6 pole stator the battery may not contain the excess for long.



Best practice is to cut off the regulator connector and crimp splice or solder the PMA wires. This is now covered in the manuals or bulletins somewhere due to wiring fires. Then crimp the red & yellow together and via fusible wire link to battery. Crimp  black wire to a ground lug and also to -ve wire to battery -ve lug.



Otherwise use wiring diagram Z20



Ralph

_________________
Ralph - CH701 / 2200a

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Mar 25, 2008 8:40 am Post subject: Wiring 3300 to an alternator switch

--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Mark Phillips in TN

Joined: 10 Jan 2006
Posts: 431
Location: Columbia, TN

Posted: Tue Mar 25, 2008 8:49 pm Post subject: Wiring 3300 to an alternator switch

Ralph-

  

 Thanks for the description- with your help, I think I have it sorted out!

  

 Appreciate the assist-

 Mark



Create a Home Theater Like the Pros. Watch the video on AOL Home.

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From The PossumWorks...

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