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1. 07:52 AM - Re: Voltage Regulator Output (user9253)
2. 08:01 AM - Re: Voltage Regulator Output (Robert L. Nuckolls, III)
3. 11:27 AM - Re: Voltage Regulator Output (MHerder)
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| Subject: | Re: Voltage Regulator Output |
Michael,
The output of the voltage regulator is not pure DC, but rather pulsing DC. Hopefully
your avionics are well designed to operate on dirty DC. If not, it might
be helpful to add some type of filter.
Your schematic does not show a switch to disable the alternator. Is there a switch?
The schematic does not show details, but it appears that the master switch
will not disconnect the alternator output from the aircraft load. But the
avionics master will isolate the avionics. I recommend that Bob Nuckolls' over-voltage
protection module be used. It will react in less than one second.
It will take a human 5 or 10 seconds to recognize a high voltage problem and
take appropriate action.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=324654#324654
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| Subject: | Re: Voltage Regulator Output |
At 03:12 PM 12/26/2010, you wrote:
><michaelherder@beckgroup.com>
>
>I am using a Jabiru 3300 with a permanent magnet alternator and a
>kubota voltage regulator. I have some questions since I don't fully
>understand the PM alternator output.
>
>1) What does the voltage out of the regulator look like on an
>oscilloscope? Is it really pure DC or does it have some squiggles
>that avionics may not do so well with?
When the regulator is running flat out (switched on hard)
the output current is what one would expect from a full-wave
bridge rectifier driven by a single phase ac source.
As bus voltage achieves the regulation setpiont, the regulator
"throttles back" an if the battery were not present, you would
no doubt see a trashier looking waveform
Noise studies on these power generating sources have
shown that the noise levels (while unique to PM alternators)
are of no more concern than the noise from a wound-field,
3-phase alternator.
>2) Jabiru suggests tying the yellow wire (senses voltage and tells
>whether or not the system needs charge or dumps excess to ground)
>and the Red wire (charges battery) as close to the positive terminal
>as possible. I would like to charge and sense voltage at the
>starter contactor for the following reason... If I have an over
>voltage situation, I will get an alarm from my EIS and I can simply
>shut off my master switch which would hopefully prevent a
>problem.... Take a look at my schematic and let me know what you think.
Why not add active monitoring and automatic control
for the OV condition as described here?
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z16M.pdf
>3) What should the voltage be at say 800 RPM, 1500 RPM and 2800 RPM?
PM alternators are usually "geared" such that full alternator
output is not available until the engine is turning at max
cruise RPM. This is why PM alternators are problematic for
meeting legacy design goals assigned to their larger 3-phase
brothers found on TC aircraft. It's unlikely that any useful
output is achieved at 800 or 1500 engine rpm. The engine
manual is silent on alternator performance data.
http://www.usjabiru.com/images/pdf/manuals/new%20stuff/3300%20Install.pdf
. . . other than to say it's rated for 200W of output
(about 14 amps).
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
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| Subject: | Re: Voltage Regulator Output |
Here's my logic... The over voltage scenario is highly unlikely with the PM alternator,
in fact the Jabiru manual does not even recommend any protection. It
seems that I could either disconnect the master solenoid which would remedy
the problem, or just turn on my landing and taxi light which draws a lot of power.
Normally the PM alternator can barely keep up with anyway. The master switch
disconnect would isolate the regulator and rectifier, however the disadvantage
is that I have no power to the main buss or avionics buss. Since I have
battery backup up on my EFIS and GPS, I'm not that concerned. I can still land
safely, which is all I'm really looking for.
The EIS should give me ample visual and audio warning if I set it for a little
lower threshold value, say 13.8V.
Michael,
The output of the voltage regulator is not pure DC, but rather pulsing DC. Hopefully
your avionics are well designed to operate on dirty DC. If not, it might
be helpful to add some type of filter.
Your schematic does not show a switch to disable the alternator. Is there a switch?
The schematic does not show details, but it appears that the master switch
will not disconnect the alternator output from the aircraft load. But the avionics
master will isolate the avionics. I recommend that Bob Nuckolls' over-voltage
protection module be used. It will react in less than one second. It will
take a human 5 or 10 seconds to recognize a high voltage problem and take appropriate
action.
Joe
--------
One Rivet at a Time!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=324689#324689
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