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Europa XS with ULPower 260i engine (OOPS!!!)

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nuckolls.bob(at)cox.net
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Posted: Sat Jan 12, 2008 5:51 pm Post subject: Europa XS with ULPower 260i engine (OOPS!!!)

I just realized that I didn't answer "the question" about justification

for OV protection.  ALL engine driven power sources fitted with regulators

have the ability to produce output voltages well in excess of the

system design voltages. RISKS from failure of the regulator are mitigated

by (1) the alternator's limited ability to deliver energy (current limit),

(2) te alternators open-circuit, runaway limits for voltage and (3) the

battery's ability to soak-up what the alternator dishes out for an interval

of time sufficient for OV protection to take notice and shut the system down.



In the case of an SD-8 driving a 18 a.h. battery, a simple OV warning light

might suffice presuming that the owner operator is willing to place him/herself

in the OV protection loop.



Most designers op for some form of automatic device as do all folks who design

systems for certified aircraft. Indeed, all of my z-figures for power 

generation

feature some form of automatic OV protection combined with immediate 

notification

of LOW VOLTAGE that follows.



I was concentrating on the operating characteristics of your particular

alternator/regulator combination and overlooked the fact that your original

question asked about the value of adding OV protection.  There are NO

votlage regualtors for which probability of runaway failure is ZERO. Some are

very good, some are not. Without doing the MTBF/FMEA analysis on every

design to be considered, the prudent thing to do is simply include OV 

protection

on every system.



This is a 3-phase machine which I presume is more robust than the 18A

alternator on a Rotax. It's probably capable of boosting bus votlage

to over 16 volts immediately followed by a steady rise to over 18 volts

in a matter of minutes. It would not be my personal choice to hope that

I would notice and react to a regulator failure for the purpose of

mitigating damage to the rest of the system . . . I would recommend

inclusion of OV protection.



To do this on the AC side of a 3-phase system would require a two-pole

relay so perhaps the best approach is leaving the relay on the DC side

so it can be a single-pole device. See figure Z-20.



   Bob . . .



At 07:49 PM 1/12/2008 -0500, you wrote:



[quote]

<vaughnray(at)bvunet.net>



Thanks Bob,



I am going down to  LSA show in Sebring, Florida to see the guys who make 

the engine. I hope it works out well for me.



Vaughn Teegarden



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vaughnray(at)bvunet.net
Guest

Posted: Sun Jan 13, 2008 7:28 am Post subject: Europa XS with ULPower 260i engine (OOPS!!!)

So if I included OV protection as shown in attached, I can feel good about 

protecting my electronics. I noticed that in Z-20, you did not have a 5amp 

alt field breaker. I have it in mine. Is it required?



Vaughn

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