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bloomfield.dh(at)gmail.co
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 Posted: Sun Dec 10, 2023 8:46 pm Post subject: Protective Regulator Wiring for Rotax 912ULS Installation |
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I'm at the stage of refitting the whole aircraft with iLevel EFIS / Auto Pilot, GRT Engine Monitoring and a UAvionix AV-30 / TailBeacon Transponder. My aircraft has a PowerMate regulator (a discontinued model with no specifications at hand).There is conflicting advice online about the wiring of non Rotax voltage regulators for Rotax 912 ULS. I have yet to look into available alternatives to the PowerMate I currently have. Regardless there is a concern about suitably protecting these new avionics. I have drafted a simple mod, as a precautionary facility and catch all solution, and I am open to informed engineering comment on it.
If the Master Switch is turned OFF while engine is running, it leads to a No-Load condition for the generator & regulator. Subject to the product make, type (and whether there is inherent built in protection for such an event), this could result in high voltage and/or current spikes onto the DC power bus and its connected avionics. I recall reading that some have acuurately measured this and found to be true. Furthermore if a Filtering Capacitor is fitted (for DC smoothing or AC noise suppression for VHF radio), it may be left in a charged state or could even be overloaded with voltages above its rating, leading to a potential capacitor fail, possibly with a lot of smoke.
From what I read, most say that Regulator Terminals B+, R and C are all connected to the load side of the master switch (or master relay), so the battery is totally isolated and cant drain back through either of the regulator terminals. Other schematics show the B+ permanently connected to the battery, and only the C & R terminals are switched off.
But there are other comments about the high potential for damage if the Master switch is turned OFF before engine is stopped, due to over-voltage and large current spikes via the generator and regulator still producing power.
In the attached schematic, The Master switch (negative switching) drives a (SPST) relay (firewall side) whereby the Load (12V Bus and Regulator) is connected to the COMMON terminal, the N.O. terminal to Battery + and the N.C. terminal to GND via a Resistor (Ceramic 100 Ohm, 10W) .
The theory is that it effectively provides a "Dummy Load" for the Regulator/Generator, and also a resitive load to discharge the Capacitor, supressing spikes into the Avionics and Pwr Bus. It's not 100% proof as there is still a tiny time frame (microseconds) of open-circuit when the Master relay contacts switch from Battery to Resistor Load. Also shoud the relay fuse and short the contacts then the worst case is a .8 Amp /10 Watt Resistive load dead across the battery , which will drain it slowly if left unattended. A warning light can be paralled across the resistor to indicate this condition.
I have yet to wire up and test the isea so are welcoming commentary.
David Bloomfield B.E.
Sydney, Australia
e: bloomfield.dh(at)gmail.com (bloomfield.dh(at)gmail.com)
mob: +61 414775225
[img]https://t.sidekickopen07.com/Cto/T5+23284/c6K6x04/R5P8b46zfW2n8QXB1krtlkW21j9FW3JD_rxW1XmJ7g3H4lG3W3LFbT81G8K-qW3yRpg01SqgjsW22yBS31N6PbTf1YBQl103[/img]
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Circuit_Diagram_Custom_-_Europa_Rotax_912_DB_Rev_1_10Dec23.pdf |
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bloomfield.dh(at)gmail.co
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| Posted: Mon Dec 11, 2023 5:09 am Post subject: Protective Regulator Wiring for Rotax 912ULS Installation |
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LINK TO WIRING Diagram below
https://drive.google.com/file/d/1Nqw3LTmfzWGjpiRX65Gen7g7ydFqnKLX/view?usp=sharing
I'm at the stage of refitting the whole aircraft with iLevel EFIS / Auto Pilot, GRT Engine Monitoring and a UAvionix AV-30 / TailBeacon Transponder. My aircraft has a PowerMate regulator (a discontinued model with no specifications at hand).There is conflicting advice online about the wiring of non Rotax voltage regulators for Rotax 912 ULS. I have yet to look into available alternatives to the PowerMate I currently have. Regardless there is a concern about suitably protecting these new avionics. I have drafted a simple mod, as a precautionary facility and catch all solution, and I am open to informed engineering comment on it.
If the Master Switch is turned OFF while engine is running, it leads to a No-Load condition for the generator & regulator. Subject to the product make, type (and whether there is inherent built in protection for such an event), this could result in high voltage and/or current spikes onto the DC power bus and its connected avionics. I recall reading that some have acuurately measured this and found to be true. Furthermore if a Filtering Capacitor is fitted (for DC smoothing or AC noise suppression for VHF radio), it may be left in a charged state or could even be overloaded with voltages above its rating, leading to a potential capacitor fail, possibly with a lot of smoke.
From what I read, most say that Regulator Terminals B+, R and C are all connected to the load side of the master switch (or master relay), so the battery is totally isolated and cant drain back through either of the regulator terminals. Other schematics show the B+ permanently connected to the battery, and only the C & R terminals are switched off.
But there are other comments about the high potential for damage if the Master switch is turned OFF before engine is stopped, due to over-voltage and large current spikes via the generator and regulator still producing power.
In the attached schematic, The Master switch (negative switching) drives a (SPST) relay (firewall side) whereby the Load (12V Bus and Regulator) is connected to the COMMON terminal, the N.O. terminal to Battery + and the N.C. terminal to GND via a Resistor (Ceramic 100 Ohm, 10W) .
The theory is that it effectively provides a "Dummy Load" for the Regulator/Generator, and also a resitive load to discharge the Capacitor, supressing spikes into the Avionics and Pwr Bus. It's not 100% proof as there is still a tiny time frame (microseconds) of open-circuit when the Master relay contacts switch from Battery to Resistor Load. Also shoud the relay fuse and short the contacts then the worst case is a .8 Amp /10 Watt Resistive load dead across the battery , which will drain it slowly if left unattended. A warning light can be paralled across the resistor to indicate this condition.
I have yet to wire up and test the isea so are welcoming commentary.
David Bloomfield B.E.
Sydney, Australia
e: bloomfield.dh(at)gmail.com (bloomfield.dh(at)gmail.com)
mob: +61 414775225
[img]https://t.sidekickopen07.com/Cto/T5+23284/c6K6x04/R5P8b46zfW2n8QXB1kQmWTW1V3gb822SqjJW1NtXC83K1FnpW3yN77-1Gbp82W25drDk1W-WtwW3Dp4v11N6PbTf1YBQl103[/img]
| | - The Matronics Europa-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:
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h&jeuropa
Joined: 07 Nov 2006
Posts: 645
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| Posted: Mon Dec 11, 2023 1:36 pm Post subject: Re: Protective Regulator Wiring for Rotax 912ULS Installatio |
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David,
Using a resistor to protect against an overvoltage event is unusual.
R and B are indeed tied together internally and are the output of the regulator. C is the regulator control and voltage sense input, so while it needs to see the bus voltage in normal operation, you might want to be able to control it although if it is disconnected from bus voltage, it will cause the regulator to turn full on and potentially cause damage. I mention this only so you understand how the regulator operates.
We all use the word regulator, but actually these devices are regulators and rectifiers combined. They take the AC output from the Rotax and rectify it to DC and regulate the DC voltage to roughly 14 volts. Again mentioned only for clarity.
I think the best solution for you is to purchase a B&C AVC-1 regulator. It is designed to control the Rotax permanent magnet alternator/dynamo. It has built in over voltage protection, adjustable output voltage and warning outputs. It also features properly sized heat sinks for the internal components. All the details are here: https://bandc.com/wp-content/uploads/2022/12/AVC1_Technical_Manual_XB100-2-TM_12-8-22.pdf
If you want to use your Powermate regulator, I’d suggest using AeroElectric Z-16 diagram as a starting point. It is somewhat innovative as it switches the AC from the alternator/dynamo before it goes to the regulator thus eliminating switching spikes. It also provides a safe overvoltage feature. I have used this in my Europa for over 1000 hours with no problems. Here is a link: http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z16M.pdf
Another consideration of your Powermate, is that many of the common regulators/rectifiers like the Ducatti supplied by Rotax and the Chinese regulators used by many are actually intended for use in lawn mowers. They often are poorly constructed and have limited current capacity. Ducatti units have a history of vibration failure and component failure when asked to carry over 10 amps continuously. Your diagram appears to have modest current requirements, probably less than 10 amps if the lights are all LED. My 914 Europa requires about 8 amps in cruise with similar equipment except no autopilot.
Hope this helps. Feel free to ask more questions.
Jim Butcher
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