overvoltage protection
 

I have the Vans F/F kit with a 60 amp alternator and built in regulator. The instructions say that a overvoltage protection is not needed and is advised against as the alt has a built in o/v protection.
As usual someone is trying to convince me to use a exterior o/voltage protector.
My question is , is it really needed? Also can the alternator pack in and toast my beautiful glass panel ?

Hi
I doubt if your alternator has built in ov protection, but again it might be something new. yes a runaway alternator will let the smoke out of the nice things in your panel. I think b&c has ov "crowbar" http://www.bandcspecialty.com/
Regards
Frank

Two choices
 

Basically you have two choices:

1) trust that your alternator will not have an OV event. These do seem to be very unlikely on new alternators.

2) put in some kind of OV protection. There is the crowbar method (see http://www.bandc.biz/), the manual method (CB in cockpit, and pilot to pull it when OV buzzer goes off), and the perihelion design method (see http://www.periheliondesign.com/). There are probably other methods that I don't know about.

If the worst thing that could happen with an OV even is that I smoke my electronics, then I would just trust the alternator, but make sure it is new. Howeve, I'll be flying with an auto conversion engine, and it needs electrons as badly as it needs gasoline. If I smoke the engine computer, I'm a glider pilot. I don't feel comfortable risking that, so I'm actively looking for a good solution.

Bob Nuckolls (http://www.aeroelectric.com/) is looking into the best way to control IR alternators, and will probably come up with some good suggestions in the coming months. If that does not happen, or I'm ready to fly before it does, then I'm going with the Perihelion Design system for IR alternators.

OV protection
 

As usual, there is no guaranteed answer. Here is a short summary of what I've learned over the past year of trying to make the same decision.

There is an ongoing discussion about IR alternators on the AeroElectric Matronics list. The big issue is getting details on how the built-in OV protection works to determine failure modes. "Can" it fry your panel - of course - if the wrong things fail, but that's true of any system. The question is, are there any components in the IR system that can allow or cause OV and also defeat the protection? No one seems to have the info to definitively answer that, and it may be different for different IR's.

A number of Van's alternators with external OV protection have fried when the B-lead contactor was opened while the alternator was under load, so obviously Van's doesn't recommend that configuration. The B-lead contactor is needed because the field coils are self-exciting once started (no way to turn off the alternator, other than disconnect the B-lead, in case of OV). If you decide to use external OV protection with a B-lead contactor, be sure to leave your Alt switch ON until the engine is shut down to avoid this problem (pretty simple solution if you want the extra protection).

Bob Nuckolls is gearing up to start playing with IR's to get some answers, but I suspect it will be a while before any answers are forthcoming. And again, it may not apply to ALL IR's.

OV is a pretty rare event, and the automotive world can't stand high failure rates on millions of vehicles with lots of on-board electronics, so many are comfortable with the protection built-in to the IR's.

One thing you can do (I plan to) is add a transorb to the B-lead which supresses voltage spikes to 18V. Eric Jones sells these as "WhackJacks" (perihelion.com). It's not the same as OV protection, but it hopefully will provide some protection for the electronics if all else fails.

I'm an AE, not an EE, so I know enough about electronics to be dangerous, but not enough to make the tough calls, like this one. Statistically, you're OK to use the built-in protection. It all comes down to your comfort level.

Dennis Glaeser
7A - Wings done! Fuselage coming...

Recent (secondhand) Experience
 

A fellow EAA'er at our local chapter just had a horendous experience with the alternator you mentioned... things were going fine till he happened to switch off and on his alternator in flight, when all heck broke loose! and he fried about 9k worth of his brand new panel! He did not have external overvoltage protection! I personally installed the BC Specalties system mentioned in the above replies in my "6" and am very happy that I did this, I would have a local alt. shop remove all internal voltage regulation from your alt. and go only with the BC Spec. regulator... not only does it have failsafe overvoltage protection, but it also has a nifty way to do fine tuning on your alternator voltage output...
Good luck
Dale - RV6 N833DW

Which alternator? What model? Where did he get it? How was it wired? How did he turn it off and on? This is the problem with second-hand info. It's incomplete.

I still don't understand why a regulator that is located outside of the alternator case is more or less reliable than one that is located inside the case. They are both regulators.

Just when you thought it was safe to go back to your web browser!
 

Maybe we should start a thread on a less-controversial topic...like primers or nosewheel vs. tailwheel. :eek:

The debate on this topic has reached almost epic proportions on the Aeroelectric List. I hope this one stays civil and technically focused...I still have a lot to learn about this stuff.

Dave

NO DON'T USE A CROW BAR with Vans Alternator
 

Frank they do have OV protection. The crow bar is a bad bad idea with internal VR alternators.

The internal VR has an IC chip that includes all the functions needed to protect from a list of possible conditions:

>SHORT-CIRCUIT FIELD PROTECTION
>SHORT-CIRCUIT LIGHT PROTECTION
>SHORT-CIRCUIT CHOKE (ACTIVE LIGHT)
>SOFT-START FREQUENCY 100HZ
>LOAD RESPONSE, 10 SECOND DELAY
>PULSE WIDTH MODULATION
>PASSES FULL LOAD DUMP
>OVERVOLTAGE, UNDERVOLTAGE, BROKEN-BELT and FAIL-SAFE INDICATOR LIGHT FUNCTIONS
>LOSS OF SENSE INDICATOR FUNCTION
>BIPOLAR TRANSISTOR
>TEMPERATURE COMPENSATION PERFORMANCE (-10MV/C)

A lot of the mis-information and myths are based on old ideas. A few other folks (not Frank) with a big soapbox perpetuate myths about internally regulated alternators, like they have no OV protection. That's totally NOT true and just ignorant. Also claims they are prone to wild "runaway" OV conditions are ball face lies with no documented cases. Yes ND alternators can fail, but they are mild or benign failures. Despite sensational comments like "smoke from your panel" or a B&C sales pitch, "On a dark stormy night your panel goes dark", internally regulated alternators are extremely reliable and safe, provide you have adequate backup, wire and operate them appropriately.

Crow Bars needlessly damage ND alternators, which are NOT designed to use them. To use a "crow bar" with an I-VR alternator, you ALSO need to add a circuit breaker and a big (master sized) relay on the output lead of the alternator (called B-lead). THIS is a lot of extra STUFF, cost and WEIGHT you are adding to an alternator that has internal OV PROTECTION. IT IS NOT NEEDED.

OK you have a crow bar on your ND alternator: "OV relay" on B-lead gets power thru a CB and crow bar attaches to the CB. If an OV is detected the crow bar SHORTS to GROUND! :eek:, POPPING the CB, cutting the power to the relay which than opens the relay (creating a big spark). OK it is all good if you had a real OV, but the problem is the CROW BAR has a nuisance trips or faults trips. This happens while the alternator is running, under load (high output). The abrupt cut of the b-lead (output) causes a huge voltage spike or LOAD DUMP. This will FRY the alternator. It has happened many times.

Hear are the facts and two guiding principals of safe alternator operations:
1) Do not run the alternator unless connected to a battery
2) Do not short or cause arcs in the wiring of the alternator.

THE CROW BAR GOES AGAINST BOTH OF THE ABOVE: 1) cuts battery from alternator, 2) Creates a large arc (internal to relay). While the crow bar shorts, it opens the relay.

Here is my suggestion:
1-Wire the NipponDenso alternator as in the application it's designed for. I HIGHLY recommend you wire in the warning light, and the remote voltage sense. The warning light is an important feature and Van ignores this. USE it. Why not? Also use the remote voltage sense by connecting direct to the battery. Van suggests you tie the IGN wire and remote sense together, which is OK, but to get the best performance from the alternator use it. Not all ND alternators have this function, but if it does why not use it. (VAN SUGGESTS A SIMPLE WIRING OF THE ALTERNATOR WHERE THE WARNING LIGHT AND REMOTE VOLTAGE SENSE ARE NOT USED. It will work this way, but recommend using the warning light at least, see ref below.)

2-Operate the alternator as it was meant in the application it was designed for (CAR). DO NOT MANUALLY TURN IT ON AND OFF THRU THE IGN WIRE POWER LEAD. The way the alternator should be used is, BEFORE engine start apply power top the IGN lead (with the master BATT switch). AFTER engine shut down turn the IGN lead off (with the BATT master). Builders are doing weird things like starting the engine with the alternator off and turning the alternator on manually after the engine is turning the alternator. This is not how it works in a car and not the intent of the IGN wire. The IGN wire comes on with the master and off with the master. If you have a problem and shut the alternative down you can turn it off then. HOWEVER the IGN wire cannot be used or trusted to shut the alternator down for a non-normal condition. (SEE NEXT PAR, item 3)


3-BIG MIS-CONCEPTION, The IGN wire is NOT a "Field Wire". The IGN wire is a Come alive or Go to sleep wire for VR power. That is it. Now some people will tell you that IF (and that's a big IF) the VR goes crazy (for a very rare and unlikely reason) you would have NO control. In this scenario the IGN wire will NOT turn the alternator OFF. This is TRUE. So how do you control an OV condition? THERE IS A SIMPLE SOLUTION: IT IS CRITICAL THAT YOU PUT A CIRCUIT BREAKER ON THE B-LEAD (alternator output), MOUNTED IN THE PANEL YOU CAN PULL. Think of it as a manual crow bar. IF for any reason the alternator is not stable or working properly you can reach over and pull the alternator's OUTPUT CB and ISOLATE the alternator positively from the aircraft. Alternator problems have signs well before a super NOVA. Have good gauges and Hi/Lo warning lights. Don't rely on the IGN wire to control the alternator. (I know it's popular to use FUSES you cannot access or replace in flight, but this concept is NOT compatible with I-VR alternators, at least use a CB for the b-lead.)

4-If you have an all-electric airplane, electric depended engine (electronic ignition / fuel injection), full EFIS panel, heated pitot and all the lights-bells-N-whistles, DONT install a 35-amp alternator. Vans alternator is rated at 60 amps, BUT it may not be big enough. It really is a 55-amp alternator. IT IS GOOD PRACTICE NOT to load the alternator continuously over 1/2 to 2/3rds of rated power. Most can live with this. However if you need more, ND has some nice alternators that put out 80 to 90 amps that are not much larger and will fit just fine. Heat kills ANY alternator.

5-PROVIDE COOLING AIR TO THE BACK OF THE ALTERNATOR. ND alternates have efficient internal dual fans and shield. However the max ambient temp is a little over 250F. Try to provide air and a heat shield between exhaust may not be a bad idea. The radiant heat from a 1400F exhaust pipe a foot away is not helping. If you keep it cool and don't over tax it the alternator will last to TBO, easily.

6- IT'S A BIG LIE THAT I-VR ARE PRONE TO SERIOUS FAILURE. I researched this and found stories of OV where just that STORIES. OV stories are left over from the OLD external VR alternators in Cessna's & Pipers. These aircraft are using 1950's technology and did have OV problems. Old VR's had mechanical relays to control voltage and no OV protection. THEREFORE THEY NEEDED AN OV MODULE ADD-ON LIKE. Many old timers think I-VR are based on this technology. FACT, an internal VR has an IC chip, with both analog and digital function, using 100's if not a few 1000 equivalent transistors. External VR's JUST regulate voltage and don't have the sophistication of INTERNAL VR's. Most E-VR's JUST regulate voltage, that's it and nothing more. A typical external VR (like the B&C unit) has 2 or 3 transistors and just a handful of other components. In fact the voltage reference in these plan external VR's use a simple zener diode reference scheme. Advanced I-VR have a much more stable voltage reference incorporated in the IC chip. There are modern external VR's, but the one B&C sells is not one of them.

WHY are all modern alternators in cars equipped with I-VR? Don't cars have expensive on-board computers and sensitive sensors (airbags) that need OV protection? Yes. That's why auto alternators have good OV protection. LOOK :eek: I checked the NATIONAL HIGHWAY SAFETY FOUNDATION database. This tracks all automotive related safety issues: Consumer complaints, Service Bulletins, Recalls, accidents related to vehicle defects. THERE HAVE BEEN NO COMPLAINTS AGAINST the alternator Van sells. This is not true of many other brands of alternators, which do have problems, but in general the ND alternator BRAND is the cream of the crop. The alternator Van sells is common in late 80's early 90's Suzuki and Geo cars. Variations of this model are found is 100's of thousands of cars and industrial equipment (forklifts, tractors) all over the world. These are going 24/7 all year round with great reliability. Some ND alternators have over 8-10 years of trouble free service in homebuilt planes. My two Acuras have a combined total of 400,000 miles and 25+ years of service, both have ND alternators still going strong.

Small Suzuki and Geo alternators are not made new anymore by ND, because today's cars need more power, even a Geo. However the new high power ND models are just larger variations of the smaller units. This leads to a point about rebuilds that some may not know. Not all rebuild alternators are the same. Pick your supplier carefully. I don't know who Van uses but you can get all new units made with after market parts. Not all rebuilds use genuine ND parts. Many aftermarket manufactures make rebuild parts. Good bad or indifferent it is something to think about.

I have checked many of the OV STORIES that I-VR allegedly had. They usually go like this: "I have a friend, and he knows some one who had an over voltage in his ND alternator in his Cessna 172." Well there are no ND alternators in factory planes. Tracking down the facts, they have nothing to do with a ND alternator or over voltage.

LEAVE THE CROW BAR OFF AS VAN SUGGEST.

George

Can you get some real FACTS?
 

Not picking on you but where are the facts?

Why did he turn the alternator off in flight?
What alternator, what model number?
What part failed?
Turning the alternator off caused a problem??
Why did he turn it off again?

Something sounds fishy here. I mean it gets your attention and is very sensational. I am not saying it did not happen, but there are some serious holes in this tale of horror, which is typical. Lets say there is some truth to it. The pilot sounds like he induced the issue but turning the alternator off under load. I really have no idea, but that is the point. There is no real data or info here, just a story. The $9,000 part sound like an exaggeration.

I know B&C would love to make this true to boost sales.

Looking at my RANT and RAVE above you should never turn a good alternator off while running under load. Master and ALT are tied together. Put a pull-able CB on the IGN wire for non-normal shut down, if you ever need to. Otherwise: (master ON, ALT on) - (master OFF, ALT off).

"IT SMOKED $9,000 WORTH OF RADIOS" I doubt that; first most modern avionics are made to a standard that allows them to survive overvoltage and can operate from about 10 volts to 32 volts continuously. Also they can survive spikes over 60 volts. Check the specs for your radio. Also if these radios are subject to severe over voltage it would burn out the power supply. Yes it would cost to get fixed but $9K, I don't think so. There are some old radios that would be damaged but still this sounds like a tall tail.

ALSO OV is a term used loosely. There are two semi documented cases where Van's ND alternator went over voltage, to about 18 volts. 18 volts is the over voltage set point of the ND alternator. Normal regulated voltage is +/-14.5 volts. In the two cases where the ND alternator started to act up the voltage rose to 18 when with alternator low load. Clearly the alternator was not working properly. IN BOTH CASES THE PILOT PLAYED AROUND WITH TURNING THE ALTERNATOR ON and OFF UNDER LOAD. NEVER DO THIS. YOU ARE MAKING VOLTAGE SURGES, SPIKES AND LOAD DUMPS.

What is a runaway overvoltage? Well it is a myth. It happens but again none I know of involving a ND alternator. Again if your Blue Mountain EFIS is destroyed with 18, 30 or even 60 volts I would return it. I know for a fact that the Dynon EFIS is protected to 60 volts. I also know if it's subject to an extreme over voltage condition the repair would be of nominal cost. (I asked)


Bob N. mentioned an anecdotal story like this on the Aeroelectric list, with no facts either. He ignored repeated request to get more info, despite his claim he was looking into it. I am sure if Bob found a smoking gun he would have wrote it up to epic levels. I think this is the same Legend.

I suspect this second hand story you mention is under the myth, urban legend and even a little duplicitous.

The thing that makes me mad is the lack of REAL good data and honest debate. People support B&C and make money at it. Great. Don't get me wrong, it is a fine product, but many B&C customers have had problems, not the least of which is the crow bar. The real comfort level with the B&C method is it's DIRT simple and easy to understand. All good attributes to be sure, and I appreciate it. There is a comfortable understanding of a simple VR circuit with 3 transistors, connected to a crow bar with another 2-3 transistors. That's cool, but there are no guarantees it won't fail, or the crow bar will fail passively, with out the pilot knowing it. I believe the crow bar also requires periodic testing to assure it will work if need. That would not fly on a Toyota. An electrical system, except the battery, should be basically 100% maintenance free.

Sensational stories are fun but of little real use, unless we have detailed facts of what and how, where, when, why it happened. I don't have an agenda, but I want the truth for others to make an informed choice, not an emotional one. I can say, in my opinion, if you are day VFR, with an engine not dependant on electrical power, by all means keep it simple, light and less expensive , use the I-VR ND alternator as is.

George

**There are some E-VR's made for marine or heavy duty vehicle use with advanced technology. Advanced E-VR's with internal OV protection, adjustable voltage control and fault monitoring can be had at 1/3rd the price of a B&C unit.

gmcjetpilot,
That was a very well thought out reply. I suspect you went thru much effort in the past to get to the bottom of this.
I in return am a complete ignoramus when it comes to electrical .
What you say does make a lot of sense though.
Where could I get a wiring diagram which shows exactly how to wire in the CB and the warning light ?
Thanks again for the enlightening reply.