Matronics Email Lists :: View topic - Over voltage with Z13/8

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Over voltage with Z13/8

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

jpx(at)Qenesis.com
Guest

Posted: Mon Dec 10, 2007 8:36 pm Post subject: Over voltage with Z13/8

I expect that typically Z13/8 is normally run in flight with the SD-8  

alternator off.

If both alternators were on, I expect the current generated would be  

dependent on which regulator is set to the slightly lower voltage.  So  

possibly the SD-8 would be at full output, with the main alternator  

picking up the slack.  Although undesirable, I expect it would not  

actually damage anything.  The opposite would be ideal really, with  

the SD-8 producing current only if the main alternator was not.



My real question though is:

If an overvoltage spike occurs, would both overvoltage modules take  

both alternators offline ?

I expect yes, and I do not see any way around it.  To do otherwise,  

would risk too long of a high voltage condition.



Should the maintenance switch option for the E-Mags that was  

previously depicted in deleted Z33 be added to Z13/8 ?



Thanks !

Jeff Page

Dream Aircraft Tundra #10

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

nuckolls.bob(at)cox.net
Guest

Posted: Tue Dec 11, 2007 6:23 am Post subject: Over voltage with Z13/8

At 11:26 PM 12/10/2007 -0500, you wrote:



 	  Quote: 	
		  



I expect that typically Z13/8 is normally run in flight with the SD-8

alternator off.


	


   yes



 	  Quote: 	
		  If both alternators were on, I expect the current generated would be

dependent on which regulator is set to the slightly lower voltage.  So

possibly the SD-8 would be at full output, with the main alternator

picking up the slack.  Although undesirable, I expect it would not

actually damage anything.  The opposite would be ideal really, with

the SD-8 producing current only if the main alternator was not.


	


   correct

 	  Quote: 	
		  My real question though is:

If an overvoltage spike occurs, would both overvoltage modules take

both alternators offline ?


	


   OV conditions are not properly described as spikes.



   The term spike is used to describe fast risetime, short

   duration, low energy events such as the transient that

   develops in the magnetic field collapse within a

   contactor coil.

 	  Quote: 	
		  I expect yes, and I do not see any way around it.  To do otherwise,

would risk too long of a high voltage condition.


	


   An OV condition is generated by loss of regulation in

   a power generating device such as an alternator or

   generator. In a OV runaway mode, the device goes into

   a max effort attempt to push the bus voltage up.

   If the bus is lightly loaded and there is no battery

   present, then the resulting scenario can lift the

   bus to some amazing and certainly damaging voltage

   levels. See:



http://aeroelectric.com/articles/When_is_110V_not_Over_Voltage.pdf



   IF a battery is present and in good shape, the

   battery will willingly attempt to soak up as

   much of the excess energy as its physics will

   allow. When a 60A alternator is launches

   for the moon, the battery will willingly

   accept 60+ amps of excess output but at a

   slightly elevated voltage. For example, some

   tests I ran and plotted a couple of years ago

   showed that a 17 a.h. battery with a 20A

   over charge rose fairly fast (10 mS or so)

   to 16 volts and then more slowly taking perhaps

   500 milliseconds to rise to 17 volts.



   Obviously, the greater the overcharge current,

   the greater will be rate of rise. I'm still

   planning on doing the full scale runaway experiments

   when I get my alternator drive stand running.



   In the mean time, know that a runaway condition

   from ANY size alternator is not a heart-stopping

   event as long as the battery is there to mitigate

   the results. An OV protection system for a 14

   volt system is generally set for 16.2 to 16.5

   volts. Between the battery's willingness to slow

   the rate-of-rise and the OV protection module's

   ability to sense and bring the event to heel in

   tens of milliseconds takes all the bite out

   of what could be a serious failure.



   The voltage plot of an OV even is a long duration,

   very high energy surge which is not a concern

   in the well maintained system (good battery)

   and artfully crafted OV protection system.

 	  Quote: 	
		  Should the maintenance switch option for the E-Mags that was

previously depicted in deleted Z33 be added to Z13/8 ?


	


   No. With the configuration shown, the Emag

   products are in the maintenance mode every time

   the bus is hot but the control switch is in

   the NON-running or OFF condition.



   Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum