OK, I got good news and bad news
Davepar said:
Looks like the mounting brackets on the new one are
steel vs. the aluminum brackets that Vans supplied/fab-yourself with the
old re-built one that I have.
Anybody know if the specs are different? As we now know from George,
not all 60amp alternators are alike. And they are rarely rated for full-time
60amp output.
Dave
This new offering is from plane power.
http://www.vansaircraft.com/cgi-bin...=alternator-kit
Here are some related links of interest from Plane Power:
(keep in mind he has certified and experimental units, the EX ones are internally regulated.)
http://www.plane-power.com/Bit3.htm
http://www.plane-
power.com/images/Brochure EXP 60.pdf
http://www.plane-power.com/Bit1.htm
http://www.plane-power.com/Bit2.htm
I don't work for plane power or claim to know the details of it other than
what I read above from his site.
First this new catalog item from Van's is NO LONGER a ND alternator. It
is a PLANE POWER (PP) alternator made with some ND parts. The
brushes, fan, regulator and pulley are all differnt from a stock unit. I am
going to guess the case, stator, rotor (field) and bearings are still ND or
aftermarket ND clone parts. One of the major things that PP has done is
modified or changed is the voltage regulator (VR) with an "external" OV
module bolted to the back. (You can see it in some of the pictures.)
In the past the method of ADDING OV protection by those who felt they
needed it was to add a BIG OV relay on the output of the alternator (B-
lead). That OV relay got power thru a "OV module" that would TRIP or
open the relay if voltage got to high. This was a bit of a kluge with a bunch
of extra components. However in theory it would open and disconnect the
alternator automatically in the event the alternator had a bad day. The down
side was the weight and cost. When using aeroelectrics "crow bar", nuisance
trips where common. This in turn could easily damage a good alternator if it
tripped. NEVER run and alternator disconnected from the battery. Nuff Said.
FIRST lets REVIEW: Remember your basic electromagnetism. When a
magnetic field is passed by a wire current it produced, Faraday's law. Well
an alternator has a spinning magnet (rotor) inside a wire coil (stator). The
output from the stator is controlled by varying the current into the rotor
("Field" is short for magnetic field, ie a spinning magnet). The stronger the
current, the stronger the "Field", the more current is produced in the stator.
Obviously RPM affects output as well. Current is passed to the rotor via the
brushes and slip-rings. If you want more power OUT (stator) add more
power IN to the rotor (field). The control of the field voltage (and thus
current) is thru a Voltage Regulator. The VR is a "negative feed back
control" device. If the sensed voltage is low it increases voltage to the
rotor, increasing the field and thus the voltage output of the stator. When
the set voltage is reached than the VR reduces the field. This goes back and
forth many times in a fraction of a second to give a steady state voltage.
(It should be noted that there are three different stator coils that produces
A/C current output or alternating current. The rectifier or diode bridge
turns the three A/C outputs into one DC output, but this is not critical to the
discussion for now, but should be mentioned.)
If the alternator's output is too high or you want to shut the output down
or you cut off all power to the field (rotor). Lets say the VR has failed and
field is uncontrolled and too high, to say the full voltage of the output. In
theory this could give greater and greater voltage in theory. The stock
regulator looks for this and has a secondary "CLAMP" to keep it from going
crazy, but there is a chance the "runaway" could still not be controlled. This
is highly unlikely but in theory possible. This is also where a secondary
redundant device, like what PP added on, comes in, to cover for this
unlikely event. Is this needed? The debate goes on and on and on.
So the old method of "emergency" shut down was cutting the alternators
output off, not the field. Apparently PP taps into the field and uses it to cut
the field off, which in turns cuts to output off, independent of the basic VR
control and protection. This is better, but it is hard to do with an internal VR
because you can not get to the "Field" wire easy. Much miss understood the
IGN wire on the ND alternator is NOT a field wire, it is the ON/OFF signal to
the voltage regulator, the go to sleep or wake up signal, not power to the
field or regulator. So both power to the regulator and field power are all
internal (power comes from the battery thru the big B-lead wire).
I think he modified a stock VR with a voltage sensing device and relay /
electronic switch to open the field current (ie cut it off). The relay/switch is
no doubt solid state. You can see it on the back of the PP alternator. Once
tripped is it shot? I don't know. I suspect once it is tripped, powering down
may reset it? You have to ask PP or Van's. It must be in the operation
instructions.
Again none of this is standard ND alternator. Is it needed. Well for the
price it ain't bad, and if it makes you feel better than it is worth the
premium.
What Van sold before where stock, Suzuki Samurai/ Nippondenso 55 amp
alternators (Van called it 60 amps. They are really rated by ND at 55 amp,
but do put out 60 amp at higher RPM's.) The stock alternator has stock
smaller dia steel pulley, cooling fan runs backward on our plane vs CW
rotation on cars, brushes are stock** and the VR is stock. (** PP claims
that stock brushes wear out faster due to lack of mosture at altitude, acting
as an abrasive? Not sure what new material he uses for brushes but they are
normally carbon, which is pretty slippery.)
The past problems with Van's ND alternator part # 14684 was quality
control of the rebuilds Van got. I am guessing but suspect that the quality
was not consistent, which is a known issue with rebuilds in the auto-
electric rebuild industry. I do know a little about PP and know that he is
using NEW aftermarket parts and think the consistency and quality are
going to be better REGARGLESS of the other modifications, since PP
buys from one source and has control over the product. With a standard
rebuild, the wholesalers can change re-builder without notice. Re-builder's
can can change the aftermarket parts vendor they use. Most all alternators
are rebuilt with Non Nippon Denso parts. They use aftermarket parts. These
parts are made all over the world, but many in Taiwan and mainland China. It
is reasonable to expect that not all have the same quality.
McFly said:
I thought that most ND IR alternators (including 60A
rebuilt units from Van) had OV smarts
I recall some posts where the ND OV condition limits the voltage to 18
volts (still an OV condition). Does this new unit shut itself down
completely? Sorry, I am still unclear what the difference is. Many
thanks.
Well YES and NO. A stock ND alternator will default to 18v typically, if the
main VR control fails. However there is a scenario where a part fails, shorts
out, bypassing the VR (working or not) and will cause an OV. Since the VR is
bypassed, in this case, you are semi-screwed. Good news NO one has any
proof or evidence this has ever happened. Of the 4 or 5 flaky ND alterantors I
looked into, all but one involved the pilot doing something not smart, like
turning it OFF and than back ON under load, so don't do that or worry. The
one was a mystery, but there was no evidence what happened and details
are sketchy. As long as you have a pull-able CB on the b-lead, if the warning
light comes on, pull the CB.
The advantage of the old alternator is it is replaceable with an off the shelf
unit at an auto-store in a pinch. If you have a PP alternator and it failed,
you could I suppose replace it with a stock alternator with some spicing-in
of a new connector plug in a pinch.
Bottom line the new alternator is way better for the reasons he states in his
web site. New parts with some quality control or consistency is the big
news. The hardware looks nice, the cooling fan is setup for counter CW
rotation, the pulley is aluminum and I think a little bigger dia, which slows
RPMs down. The secondary OV control unit on top of the basic control is a
nice thing. The brush wear thing is a bit of a mystery to me, but he must use
a differnt material?
The new alternator kit is better than the rebuilt product, not because the
OV module hanging off the back but because of QC. Not all aftermarket parts
are the same from my research. I think he took the time to get the better
vendors from what I heard. I would consider it and likely buy it. At $823 for
B&C, no way.
There is nothing wrong with the stock ND alternator. It is fair to say there
was no real control, knowledge about vendors and changes in parts used. If
you want the new PP unit, sell your existing unit and buy the PP unit, or keep
what you got, it is fine.
Sorry I can't predict the future. I don't have the service history on the PP
because it is new. I know the stock units work GREAT, if you install it, wire it
and operate it properly.
Cheers George
