NO DON'T USE A CROW BAR with Vans Alternator
FrankK90989 said:
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
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!
, 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 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
