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Author Topic: Power Systems  (Read 21877 times)

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Offline Ededge2002

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Power Systems
« on: February 04, 2013, 08:38:04 PM »
At the recient meeting there were several great questions that I did my best to answer and peaked me to do more reading.  There are some great resources available to us as electric flyers thanks to some very bright people involved in the hobby and using the search function.  I found one thread/post in particular that answered several of these questions AND in easy to understand terms.  Please take the time to look over the post as It might answer some of your questions and help us all to build/fly better performing models.  Win Win!

You dont have to go on the wild chase following the links the post provides the mainstay of the information.  That is unless you want to!  PS the link has some great photos if interested.

(http://www.rcgroups.com/forums/showpost.php?p=10926525&postcount=1)

Quote origional post in link provided:

too long battery wires will kill ESC over time: precautions, solutions & workarounds

--------------------------------------------------------------------------------

I have copied (parts of) useful posts in this thread into this opening post.


Problem
Solution
Rule of thumb

Capacitor type
Capacitor polarity!
How to add extra capacitors
Expert/manufacturer opinions, rules of thumb, installation
Explanation/theory
Measurements
DIY pictures


Problem
Conclusion from the links below, all controller manufacturers say the same:
Too long battery wires will kill your ESC over time!
The standard input capacitors (large cylindrical thingies in thin shrink wrap) will be destroyed over time because they get warmer/hotter. Using thicker wire will not help, it's mainly a wire inductance problem, not a resistance problem.

This goes for all makes, they all use the same principle (except Sinus controllers, they use sinusoidal commutation instead of trapezoid, they tested 70 meters without capacitors). However, lengthening the motor wires may lead to radio interference. Give the three of them a twist to prevent this.

Solution
Lengthen the motor wires, not the battery wires. That's hardly critical because there's already a lot of wire in the motor itself. If the motor-ESC wire eventually gets too long, it will not harm motor and/or controller. May cause interference though, give the motor-ESC wires a twist. Always a good idea to do that anyway.

Rule of thumb
If you have to lengthen the battery wires, add extra electrolytic capacitors in parallel with ESC, never in series with ESC. As a rule of thumb, for every 4inch/10cm extra length/distance between battery and ESC, add an 220uF extra capacitance near the controller (electrolytic condensators, voltage the same as the capacitors already installed, low ESR type) (Ludwich Retzbach, German e-flight author&editor, the 'R' in LRK).
Better to use several smaller caps (in parallel) instead of one biggie. Smaller caps can shed more heat and total inductance will be lower (inductance per cap is lower and those inductances are paralled to boot  ). See attached pictures below.
Also keep the positive and negative wires as close to each other as possible, eg. by twisting and/or taping them together. If the wires are close to each other then the series inductance will be reduced, because the current is going in opposite directions in each wire (and therefore producing opposite polarity magnetic fields which cancel out). For example, 13AWG wires separated from each other by 1 inch have about 4 times higher inductance than if they are bound together. (Bruce Abbott in www.rcgroups.com/forums/showthread.php?p=11594609#post11594609)

Capacitor type
The main spec you need is low impedance and low ESR(equivalent series resistance). I think the only thing you will find at radio shack will be general purpose caps, not low ESR. The ESR of a cap won't be printed on it, you will have to look up the manufacturers spec sheet. The Rubicon ZL series mentioned in the Schulze instructions is a good one and is available from newark/farnell. The Panasonic FM series is another good low impedance cap and is available from digikey
www.farnell.com/datasheets/2161.pdf
industrial.panasonic.com/www-data/pdf/ABA0000/ABA0000CE108.pdf
PS You would want the voltage rating on the caps to be significantly higher than the battery voltage. Same voltage rating is the installed caps. Higher rating is no problem. (thanks jeffs555, from www.rcgroups.com/forums/showthread.php?p=11971048#post11971048)
If you try it with longer wires and no extra low esr caps it may work for a while, but the longer wires put an extra load on the original cap. The extra load shortens the life of the original cap and it will eventually fail, probably catastrophically. (thanks jeffs555, from www.rcgroups.com/forums/showthread.php?p=11996840#post11996840.

Capacitor polarity!
Electrolytic capacitors, like batteries, have a (+) and (-) lead! Solder them in the wrong way and they will got hot, pop open or even explode. Nasty fumes and the liquid stains. Don't ask how I know

How to add extra capacitors (English and German)
www.schulze-elektronik-gmbh.de/guide/gfutc-de.pdf
YGE controllers, extra capacitors and their location, nice pics, click to enlarge:
www.yge.de/caps2.php

Expert opinions, rules of thumb, installation
Schulze controllers and battery lead length
www.schulze-elektronik-gmbh.de/tips_e.htm (English)
www.schulze-elektronik-gmbh.de/tips_d.htm (German)
Castle Controllers about battery lead length
www.rcgroups.com/forums/showpost.php?p=1537846&postcount=28
www.rcgroups.com/forums/showpost.php?p=4833040&postcount=5
www.rcgroups.com/forums/showpost.php?p=1531363&postcount=25
www.rcgroups.com/forums/showthread.php?t=1095329
Bob Boucher (Astrobob, www.astroflight.com) on long battery leads
www.rcgroups.com/forums/showpost.php?p=2988042&postcount=32
Hacker on long battery wires:
www.hacker-motoren.de/images/Master-manual-Engl.pdf (English)
-> Safety and operating instructions
www.hacker-motoren.de/images/MASTER-Manualgerman.pdf (German)
-> Sicherheits- und Betriebshinweise
Novak
www.teamnovak.com/tech_info/power_caps/power_caps.htm
Paul Daniels
www.rcgroups.com/forums/showthread.php?p=11297012#post11297012

Explanation/theory
First a watery analogy, water running in a pipe and through a tap. Now turn off the tap quickly. You'll hear a loud knock/shock sound in the pipe. The water wants to continu flowing but it can't, for a moment the water pressure is much higher than the static water pressure. It's the same for a current that's switched off, because of the inductance it wants to keep on flowing, voltage gets higher. This is also what causes sparks (brush fire) in a brushed motor.

The controller is like a watertap that's switched off (and on) very fast (8,16, 32kHz PWM) to get the desired current. Turning off the current, in combination with the battery wire inductance, causes voltage spikes because the current wants to continue on its course (ref. inertia of the moving watercolumn). Those voltages are higher than the battery voltage. The input capacitors (cylindrical) takes care of these spikes (they reduce the wire inductance). The longer the wires, the higher the voltage spikes induced in the wires, the harder on the input capacitors. They will get warmer, heat up and explode. This is caused by the wire inductance, not by wire resistance. Therefore, using thicker wire will not help much, it's not a bad idea either, but extra capacitors are the solution, thus reducing/compensating the wire inductance. Or longer motor wires instead of long battery wires.

www.s4a.ch/eflight/reglerleistung.pdf (German)
-> Akkukabellänge und seine tödliche Auswirkung
The coils switching off create the high voltage spikes in the battery wires:
www.rcgroups.com/forums/showthread.php?p=10940134#post10940134
In depth discussion
www.aerodesign.de/peter/2001/LRK350/SPEEDY-BL_eng.html
www.aerodesign.de/peter/2001/LRK350/Warum_dreht_er_so_eng.html
www.rcgroups.com/forums/showpost.php?p=10028325&postcount=2661
www.rcgroups.com/forums/showthread.php?p=1518827#post1518827

Measurements
By RCGroups user Peter D Rieden
www.rcmf.co.uk/4um/index.php/topic,50366.msg569630.html#msg569630

Vriendelijke groeten  Ron van Sommeren
• brushless motor building tips & tricks
• diy brushless motor discussion group
• Drive Calculator download & discussion group
• int. electric fly-in, Nijmegen, the Netherlands


DIY pictures
more pictures at www.YGE.de controllers
Han Witteveen (Netherlands ) posted his diy solutions in post #49
Building the Haviland DH-84 VH-UXG 'Riama' workshop cam
 
« Last Edit: February 04, 2013, 08:42:21 PM by Ededge2002 »


Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?

Offline Bobmic

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Re: Power Systems
« Reply #1 on: February 04, 2013, 09:16:53 PM »
Hey Ed - Thank you for the great summary ! 
Can you add a link to the propeller graph/power data you showed?

Thx
Bobby

Offline Ededge2002

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Re: Power Systems
« Reply #2 on: February 04, 2013, 09:28:41 PM »
This is one of the links I used to produce the graphs

http://www.peakeff.com

`search for a motor`

just a tip that E-Flite is listed as I typed it.
« Last Edit: March 15, 2013, 07:55:10 AM by sihinch »
Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?

Offline sihinch

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Re: Power Systems
« Reply #3 on: February 04, 2013, 09:38:21 PM »
Wow, thanks Ed.

That means I need to re-locate my ESC in the Hunter.

Does the ESC have to be in airflow?

And are there any problems putting the esc near the battery?

Offline Ededge2002

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Re: Power Systems
« Reply #4 on: February 04, 2013, 09:50:49 PM »
Airflow over the ESC is recommended. You don't need huge air just moving air usually is enough.  A good point to figure it out is with some static runs and see how quickly it heats up as the variations if ESC's are limitless.
Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?

Offline thehaze

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Re: Power Systems
« Reply #5 on: February 04, 2013, 10:09:48 PM »
Moved to construction forum and set as a sticky. Lots of good info here for any build.
Takeoffs are optional. Landings are mandatory.

Offline Andy Hoffer

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Re: Power Systems
« Reply #6 on: February 05, 2013, 12:24:02 PM »
Ed, thank you so much for these fantastic posts!  This is a gold mine of really practical and important information, especially for folks building larger and multi-motor planes with longer wire runs.  Your summary is excellent and you have provided great guidance and excellent links for follow up reading.

This is even better than an ARF for Christmas !!

Cheers!

Andy

Offline Papa

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Re: Power Systems
« Reply #7 on: February 05, 2013, 01:06:46 PM »
Inductance?
Should battery leads also be taped or even twisted together?
Does it matter if the signal lead is twisted as part of the motor leads?


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Offline Ededge2002

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Re: Power Systems
« Reply #8 on: February 05, 2013, 02:27:16 PM »
My understanding is ESC power leads taped together. Motor wires twisted but not twisted with signal leads.   Would recommend lots of range testing.


Inductance?
Should battery leads also be taped or even twisted together?
Does it matter if the signal lead is twisted as part of the motor leads?


Jack.
Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?

Offline sihinch

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Re: Power Systems
« Reply #9 on: February 05, 2013, 03:24:23 PM »
When you say not twisted with signal lead, you mean the three main motor wires should be twisted, but the lead going to the rx is not?

Offline Ededge2002

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Re: Power Systems
« Reply #10 on: February 05, 2013, 11:41:51 PM »
Jack was wanting to run servo signal leads parrallel to motor wires I understand.  yes twisting the motor wires(Red Black White).

When you say not twisted with signal lead, you mean the three main motor wires should be twisted, but the lead going to the rx is not?
Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?

Offline sihinch

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Re: Power Systems
« Reply #11 on: February 10, 2013, 04:45:44 PM »
I think I know the answer to this, but may as well check with all you more experience electrical Guys.....

When it comes to soldering ESC or motor leads, when I'm expecting around 80-100A, which type of solder joint is better - 1 or 2 (see picture)?

Offline battlestu

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Re: Power Systems
« Reply #12 on: February 10, 2013, 06:29:10 PM »
"I'm disrespectful to dirt. Can you see that I am serious?"

Offline Papa

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Re: Power Systems
« Reply #13 on: February 10, 2013, 07:09:34 PM »
Option 2 is what I do all the time with good shrink tube over each join. You have to "tin" each end first and use a good flux with an 80 watt iron.

If you use option three make sure you do not use wire off a coil for a bell or magnet. That wire is coated and will never solder.

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Offline Ededge2002

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Re: Power Systems
« Reply #14 on: February 12, 2013, 02:12:10 PM »
Yes, yes but NEVER #1

Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?