flyrotary@lancaironline.net Mailing List Archive

Group,

I found the following discussion on the Bob Nuckolls "AeroConnection" site that would

seem to add credence to my opinion about the modification of internal regulated alternators

to external regulation.............FWIW

Alternator Internal Regulator

> I was sure hoping someone knew what could cause the voltage regulator to go out on the ND

internal regulated alternator. Repair shop said I may have shorted out the alternator light circuit

which in turn can cause the regulator to fail. I did mount my relay using one of the existing three

bolts that appear to run through the back of the alt but they are not connected to anything I am

aware of. I used a smaller lighter high amp relay instead of the big contactor. Any thoughts

would be most welcome.

A Use of an automotive alternator with built in regulator has some risk associated with it.

There ARE failure modes within the regulators that may precipitate uncontrollable voltage

run-away. By-in-large, the warning light driver built into these products are not terribly useful . . .

the ONLY all inclusive warning system for monitoring alternator performance should be a low

voltage sensing system that lights up for bus voltage below 13.0 volts. Ignore the built in lamp

circuit.

I presume the "relay" you cited is for the external ov protection. If I interpret your words

correctly, you have mounted a relay right on the back of the alternator. This is not

recommended. This subjects the relay to much higher vibration levels from the engine than it

would experience if mounted on the firewall.

I gotta be honest with you folks . . . I have published work-arounds for letting you "get

by" with internally regulated alternators . . . I DON'T RECOMMEND THEM. When we design

new systems for aircraft, I really lean on my compatriots to reduce if not eliminate relays in the

system. Relays, especially those that carry heavy current -AND- get vibrated are some of the

poorest performance devices in the airplane. This is why our latest and greatest Mach 2.5 GPS

guided target has NO RELAYS in the power distribution system. I'd really like to see the

automotive alternators get modified to use external regulation. Bob . . .

------

Alternator

>> Bob , any thought on why the alternator would not shut down even after the field was cut. It

went to 28 volts. I have an order with you for the Over voltage protection that's for sure. Richard

A Sure . . . it's because MANY if not ALL automotive alternators have failure modes that

can BYPASS the effects of any control circuits for a normally operating alternator. This is why

we've always suggested that really nice automotive products be modified for external regulation

and ov protection so that we can be sure of performance in a failed regulator situation. You'll

also need an alternator disconnect contactor to go with your ov module . . . the ov module is

capable of shutting down an externally regulated alternator with no assistance. An

INTERNALLY regulated alternator needs to be physically disconnected from the bus in an OV

condition. See: http://aeroelectric.com/articles/bleadov.pdf Bob . . .

-----

--
Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold

-------------- Forwarded Message: --------------
From: "Kelly Troyer" <keltro@att.net>
Subject: [FlyRotary] Re: Modify Alternator for External Regulator
Date: Sun, 05 Jul 2009 17:08:28 +0000

Group,

I appreciate all the different opinions and perspectives about this subject............Each of us as

experimenters has to decide for themselves their comfortable risk level...........I currently have a

Mazda alternator modified as described on my Chevrolet V6 powered 1988 RX7 with about

60,000 miles on the conversion (My 13B lost compression <apex seal> and I feel Rotarys are

wasted in cars so will now power my Dyke Delta)...............The internal regulator failed but

failed open instead of an internal short which would have allowed runaway voltage.........I do

realize that the majority of failures fail open , "But" my personal risk level still wanted the ability

to switch off field voltage and shut the alternator down in my "Delta"...........I do not currently

have a switch in the field circuit of my RX7 but will be installing one to test this as there has

been some discussion that residual magnetism in the fields might prevent the alternator from

shuting down............Will report my findings...........

I realize that abilities among experimental aircraft builders vary but in my opinion if you

can build a safe and flyable aircraft with a Mazda Rotary engine then the skills needed to

modify a Mazda alternator should be no problem...........This is not rocket science , all you

are doing is removing an internal regulator (I think the entire circuitry should be removed as

I previously stated) the brushes connected to ground and the field windings connected to

a now unused external connector..........Until the advent of the internal regulator alternators

were all built this way electrically.............IMHO & FWIW

--
Kelly Troyer
"Dyke Delta"_13B ROTARY Engine
"RWS"_RD1C/EC2/EM2
"Mistral"_Backplate/Oil Manifold