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nuckolls.bob(at)aeroelect
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 Posted: Thu Aug 10, 2023 9:00 am Post subject: Simple sequencing using common 5-pin auto relays |
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| Quote: |
IIRC, "start power" is for powering the electronic lanes and pumps until the engine alternator takes over. In my experience it took some time until the engine was "autonomous". |
I presume we're discussing a cranking, brown-out event.
If so, the goal is to establish a lower limit for which
brown-out vulnerable appliances are powered while the
starter has a battery loaded down.
Some of you may recall some discussions and experiments
leading to practical brownout mitigation using super
capacitors to deliver energy for the few tens of
milliseconds that starter inrush currents were
loading the battery.
Other designs were proposed not the least of which
utilized boost converters. Others used an array
of LiFePO4 cells capable of grunting a few amps
for the necessary duration.
ALL of these proposals were millisecond fast
using diodes and/or relays to accomplish switching.
No pilot intervention necessary.
Any time a flight system presents shortcomings
that require pilot intervention increases risk
for mis-positioning of controls. This is indicative
of a missed opportunity to keep tomorrow's
systems as simple as yesterday's.
Adverse sensitivity to bus voltage perturbations
are not a new thing . . . appliance qualification
for certified aircraft have required jumping
those hoops for nearly a century.
It up to us as consumers of nifty new gadgets to
hold would be suppliers to equivalent requirements.
Did it for over 40 years . . . it ain't hard!
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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Voyager
Joined: 30 Jun 2020
Posts: 77
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| Posted: Thu Aug 10, 2023 9:42 am Post subject: Simple sequencing using common 5-pin auto relays |
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Hi Bob,
No, this isn’t related to low voltage during cranking. This is a unique issue with the Rotax design being an all electric engine. It powers its two ECUs, two fuel pumps, fuel injectors, spark plugs, etc. from an internal generator called generator A. These systems are completely independent from the airframe electrical system including have a separate ground reference. There is a second, larger, generator B which powers the airframe during normal operation.
There are essentially three phases that occur during engine start and initial operation.
Phase 1 where two switches are employed, one which interconnects the independent ground with the airframe ground and the other which provides battery power to the engine to run the ECUs, fuel pumps, et al, during engine cranking and initial operation below 1,500 RPM when generator B is not providing sufficient power to operate the engine.
Phase 2 begins at 1,500 RPM where generator B takes over operation of the engine and now the two switches in phase 1 are opened removing battery power from the engine and isolating the two grounds such that the engine management system has an isolated ground.
Phase 3 which begins, if I understand the manual correctly, when the engine is revved to 2,400 RPM or higher and held for at least 8 seconds. In this phase, generator A now takes over operation of the engine and generator B is switched to provide power to the airframe
The “start power” I mentioned in my post is that which is provided to the engine in Phase 1 and then released once the engine is above 1,500 RPM.
Many kit planes use separate momentary switches for start power and starter engagement and the pilot has to hold the start power switch for several seconds to allow the ECUs to power up and self-test, continue holding start power while pressing the starter switch, and then releasing both after engine start, but not release too soon before generator B has taken over powering of the engine. This seems overly complicated to me so I am trying to design a system where the start power can be latched on via a momentary actuation of the start power switch with no need to hold it closed and then the starter button can be pressed normally to crank the engine and then released once the engine fires and also have the start power release automatically also with proper timing with generator B taking over.
Clear as mud?
Matt
Sent from my iPad
| Quote: | On Aug 10, 2023, at 1:03 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:
 | Quote: |
IIRC, "start power" is for powering the electronic lanes and pumps until the engine alternator takes over. In my experience it took some time until the engine was "autonomous". |
I presume we're discussing a cranking, brown-out event.
If so, the goal is to establish a lower limit for which
brown-out vulnerable appliances are powered while the
starter has a battery loaded down.
Some of you may recall some discussions and experiments
leading to practical brownout mitigation using super
capacitors to deliver energy for the few tens of
milliseconds that starter inrush currents were
loading the battery.
Other designs were proposed not the least of which
utilized boost converters. Others used an array
of LiFePO4 cells capable of grunting a few amps
for the necessary duration.
ALL of these proposals were millisecond fast
using diodes and/or relays to accomplish switching.
No pilot intervention necessary.
Any time a flight system presents shortcomings
that require pilot intervention increases risk
for mis-positioning of controls. This is indicative
of a missed opportunity to keep tomorrow's
systems as simple as yesterday's.
Adverse sensitivity to bus voltage perturbations
are not a new thing . . . appliance qualification
for certified aircraft have required jumping
those hoops for nearly a century.
It up to us as consumers of nifty new gadgets to
hold would be suppliers to equivalent requirements.
Did it for over 40 years . . . it ain't hard!
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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