Motor formulas

fly_boy99 · Oct 24, 2006, 02:55 PM

I thought it would be a good idea to have a sticky around motor formulas we constantly use here in the EMD&C section. If there is an error please PM me instead of posting here.

Please add new formulas as you see fit but please do not clutter this stickey with commentary. If you wish to do that start your own thread. Thank you.

=======
Efficiency

Motor Efficiency = Pout/Pin
Pout = (Vin - Iin * Rm) * (Iin - Io)
=======
Motor Kv

Kv = RPM / (Vin - Vloss)
Vloss = Iin * Rm
=======
Motor RPM

RPM = Kv * (V - Vloss)
Vloss = Iin * Rm
=======
Watts

Watts = V * Iin
Alternately P=I²R (P = I x I x Rm)
=======
Stalled Motor

Istall = Vin / Rm
=======
Torque constant

Torque constant: Kt=Kb x 1.345
Kb = Voltage constant (Volt/1000 RPM)
=======
Torque Loss

Torque = Kt * (Iin - Io)
=======
Termination

Wye = the number of winds you have performed
Delta = divide the number of turns by 1.73
=======
Watts per Horsepower

1 horsepower = 746 watts
=======

Acronyms
=======

Rm = Resistance value of the motor, derived from the guage of wire used

Pout = Power Out of the Motor expressed in Watts

Pin = Power In of the Motor expressed in Watts

Vin = Voltage Into the Motor

Iin = Current Into the Motor

Io = Noload Current of the Motor, derived from running a motor WOT without a prop at varying voltages. Io can be expressed with an associated Voltage and should be.

Kv = K value or voltage constant, the expressed value where the rpm can be surmised by a given voltage. For a 2000 Kv motor an input voltage of 10V would net 20000RPM.

Istall = The load current of a motor which is purposely stalled, hence not turning

Kt = Torque constant (oz-In/A)

Kb = Voltage constant (Volt/1000 RPM)

Note: Data has been gathered and utilized from various sources such as the aveox site as well as others.

Ron van Sommeren · Oct 25, 2006, 06:57 PM

Not exactly formulas:
Doubling the number of winds halves Kv (rpm/volt) and doubles Kt (torque/Ampere)
Doubling statorheight halves Kv, doubles Kt and (roughly) doubles maximum power.

tomekr · Apr 13, 2007, 02:28 PM

Max power (with akceptable efficiency) of the motor is about
Pin[W]=1600*Vmagnet[inch^3]
Pin[W]=0.1*Vmagnet[mm^3]
This formula is based on practice, and work well on neodym magnet. It is very usefull to calculate an appropriate max. supply voltage, rpm, proppeler etc. (based on the motor resistance and expecting efficiency or simply optimal motor current)

Fourdan · May 12, 2007, 06:17 PM

About termination

Kv ratio = 1.732 is a controversy
A lot of testers found a ratio between 1.78 and 1.9
Louis

marc780 · Sep 20, 2007, 05:05 PM

huh?

flyman77 · Sep 29, 2007, 09:12 AM

How does one calculate how many magnets to use against the number of poles, and what decides the winding direction? Anyone please?
Thanks Brian

heliovaitsman · Oct 26, 2007, 01:47 PM

PLEASE SOMEBODY HAVE AN ELECTRIC CIRCUIT OF ELECTRIC MOTOR BRUSHLESS 12 POLES 14 MAGNETOS? THE MOTOR IS Z3007-26 HYPERION
the bindings betweem wires are delta or star?
TKS
Hélio Vaitsman

Spiritosl · Oct 28, 2007, 10:41 AM

Quote:

Originally Posted by flyman77

How does one calculate how many magnets to use against the number of poles, and what decides the winding direction? Anyone please?
Thanks Brian

Brian and others,
try this one! I found it on a German site three years ago

http://www.rclineforum.de/forum/thre...did=60302&sid=

Copy the program below (in dark red starting with <HTML> and ends with </HTML>) in Notes and save it as Poles and magnets.html and run it as a Java program.

<html>
<head>
<title>Schematic for electric motor windings</title>
<style type="text/css">

</style>

<script language="JavaScript">

</script>

<script language="JavaScript">

// Lizenz:
// Verwendung und/oder Modifikation für eigene Homepage
// nur mit folgendem Verweis auf das Original:
// http://www.maltemedia.de/brushless/wicklungsschema/
// (C) 2004 overclocker_2001 alias oc2k1 & DrM (drmalte@maltemedia.de)
//
// Modifikation nur mit dem Einverständnis, daß die Modifikationen
// auch in das Original eingebaut werden dürfen.

function init()
{
document.Windungsrechner.Nuten.focus();
document.Windungsrechner.Nuten.value = "";
document.Windungsrechner.Pole.value = "";
document.Windungsrechner.Ergebnis.value = "";
}

function berechnen( form )
{
Nuten = eval( form.Nuten.value );
Pole = eval( form.Pole.value );

if( Nuten % 3 != 0 || Nuten < 3 ) {
document.Windungsrechner.Ergebnis.value = "Pole number must be divisable with 3!";
document.Windungsrechner.Nuten.focus();
document.Windungsrechner.Nuten.select();

return;
}

if( Pole % 2 != 0 || Pole < 2 ) {
document.Windungsrechner.Ergebnis.value = "Magnet number must be an even number!";
document.Windungsrechner.Pole.focus();
document.Windungsrechner.Pole.select();

return;
}

if( Pole == Nuten ) {
document.Windungsrechner.Ergebnis.value = "Pole number must be different from magnet number!";
document.Windungsrechner.Pole.focus();
document.Windungsrechner.Pole.select();

return;
}

Winkel = 180 * Pole / Nuten;
a = 0; b = 0; c = 0;
A = 0; B = 0; C = 0;
schema = ""
summe = 0;

for( i = 0; i < Nuten; i++ ){

if( summe >= 330 || summe < 30 ) {
schema += "A";
A++;
}

if( summe >= 30 && summe < 90 ) {
schema += "b";
b++;
}

if( summe >= 90 && summe < 150 ) {
schema += "C";
C++;
}

if( summe >= 150 && summe < 210 ) {
schema += "a";
a++;
}

if( summe >= 210 && summe < 270 ) {
schema += "B";
B++;
}

if( summe >= 270 && summe < 330 ) {
schema += "c";
c++;
}

summe = ( summe + Winkel ) % 360;
}

if( a == b && a == c && A == B && A == C ) {

while( schema.charAt(schema.length-1) == 'a' || schema.charAt(schema.length-1) == 'A' ) {
schema = schema.charAt(schema.length-1) + schema.slice( 0, -1 );
}

if( schema.charAt( 0 ) == "a" ) {
schema = schema.replace( /a/g, 'x' );
schema = schema.replace( /b/g, 'y' );
schema = schema.replace( /c/g, 'z' );
schema = schema.replace( /A/g, 'a' );
schema = schema.replace( /B/g, 'b' );
schema = schema.replace( /C/g, 'c' );
schema = schema.replace( /x/g, 'A' );
schema = schema.replace( /y/g, 'B' );
schema = schema.replace( /z/g, 'C' );
}

if( schema.search( /[bB]/ ) > schema.search( /[cC]/ ) ) {
schema = schema.replace( /b/g, 'x' );
schema = schema.replace( /c/g, 'y' );
schema = schema.replace( /x/g, 'c' );
schema = schema.replace( /y/g, 'b' );
schema = schema.replace( /B/g, 'x' );
schema = schema.replace( /C/g, 'y' );
schema = schema.replace( /x/g, 'C' );
schema = schema.replace( /y/g, 'B' );
}

document.Windungsrechner.Ergebnis.value = schema;

} else {
document.Windungsrechner.Ergebnis.value = "Invalid combination! ("+schema+")";
}
}

</script>
</head>

<body bgcolor=white onload="var SymTmpWinOpen = window.open; window.open = SymWinOpen; init(); window.open = SymTmpWinOpen;">
<form name="Windungsrechner">

<BR><BR>
<div align="center"><center>
<!-- <B>Scrift is still working, please be patient

</B><BR> -->
<B>Motor winding schema V1.0</B><BR><BR>
Dial in pole and magnet numbers and press = or press ENTER.
<BR><BR>
<table border="1" cellpadding=5 CELLSPACING=0>
<tr>
<td>Poler:</td>
<td><input type="text" size="3" name="Nuten" maxlength="3"></td>
<td>Magneter:</td>
<td><input type="text" size="3" maxlength="3" name="Pole"></td>
<td><input type="submit" name="Berechnen" value="=" onclick="berechnen(this.form);return false;"></td>
<td><input type="text" size="64" name="Ergebnis" readonly class=result></td>
</tr>
</table>
<BR>

<BR><BR>
<A HREF="http://www.rclineforum.de/forum/thread.php?threadid=60302&sid=">Source: http://www.maltemedia.de/brushless/wicklungsschema/
<BR> (C) 2004 overclocker_2001 alias oc2k1 & DrM (drmalte@maltemedia.de)</A>
<BR>Translated from German into English by Björn Hammarskjöld, Mora, Sweden, 2007
</center>
</div>
</form>
<p></p>
<noscript>
Please activate Javascript
</noscript>

<a href="http://www.maltemedia.de/brushless/wicklungsschema/source.txt">Source</a>

</body>

<script language="JavaScript">

</script>

</html>

Ron van Sommeren · Oct 28, 2007, 11:35 AM

Quote:

Originally Posted by flyman77

How does one calculate how many magnets to use against the number of poles, and what decides the winding direction? Anyone please?
Thanks Brian

Excellent motor building articles by Brian Mulder, a must read, will prevent you from asking a lot of questions you even did not know you were going to ask

http://www.southernsoaringclub.org.za/
-> Articles by SouthEasterners.
-> Electric Motors - part 1-5
-> Table in chapter 3

Or www.powercroco.de
-> konstruktion
-> kombinationstabelle

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:
http://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum)

Vriendelijke groeten

Ron van Sommeren
• diy brushless motor discussion group
• Drive Calculator download & discussion group
• int.electric fly-in & diy outrunner meet, Nijmegen, the Netherlands

jimweda · Dec 18, 2007, 08:46 PM

Quote:

Originally Posted by Ron van Sommeren

Not exactly formulas:
Doubling the number of winds halves Kv (rpm/volt) and doubles Kt (torque/Ampere)
Doubling statorheight halves Kv, doubles Kt and (roughly) doubles maximum power.

I've seen a few posts that you have made on forums regarding motors and you seem to know your stuff. I've only been in the RC arena for about 4 months now but this is my background. I learned to fly planes on a Stryker F-27C, went to Hanger 9 F-22 Raptor (Nitro, which I do not like now, prefer electric) and from that point I've been flying FunJets (3 with Mega 16/15/3 (3000kv) & Align 430XL (3770kv), Kyosho F-16 EDF and Phase 3 F-16 EDF. Here's my question. I've been told by a couple people that I could actually make my own motors which is why I am here, researching. You seem to be one of the guys to talk to. This is what I am trying to attempt. I want to take the last 3 planes mentioned and make them scream and would like your advise on how to make motors that will make these birds scream. I know its not as simple as that, but I was hoping you could point me in the right direction towards winding my own motors to suit my needs. Currently for the Phase 3 F-16 the fastest flyers seem to be running Typhoon 2W & 2W-20/23's with Wemo mini fans or Alfa 5 blade fans. Others motors are Little Screamer Jet Screamers and a new Monster Jet Screamer that hasn't been released yet. I was talking to the R&D guy who is putting it into a WM400 fan unit and they're talking about doing about 160 - 170 mph with that set up. Can I make motors that will help me reach at least 120 mph or more by either prop or fan unit? I would sincerely appreciate any information you might pass my way. Thank you in advance and I look forward to hearing from you and others in the forum.

Jim

Ron van Sommeren · Dec 19, 2007, 06:51 AM

I cannot help you with motor size, winding numbers etc. for your plane, for that you need input from people who have experience with those planes.

Excellent motor building articles by Brian Mulder, a must read:
http://www.southernsoaringclub.org.za/
-> Articles by SouthEasterners.
-> Electric Motors - part 1-5

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:
http://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum)

Vriendelijke groeten

Ron van Sommeren
• brushless motor building tips & tricks
• diy brushless motor discussion group
• Drive Calculator download & discussion group

jimweda · Dec 19, 2007, 05:27 PM

Quote:

Originally Posted by Ron van Sommeren

I cannot help you with motor size, winding numbers etc. for your plane, for that you need input from people who have experience with those planes.

Excellent motor building articles by Brian Mulder, a must read:
http://www.southernsoaringclub.org.za/
-> Articles by SouthEasterners.
-> Electric Motors - part 1-5

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:
http://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum)

Vriendelijke groeten

Ron van Sommeren
• brushless motor building tips & tricks
• diy brushless motor discussion group
• Drive Calculator download & discussion group

I appreciate your honesty, quick response and links to resources that may get me where I want to go. Thanks again.

Jim

barney 69 · Aug 11, 2008, 12:13 AM

Quote:

Originally Posted by fly_boy99

=======
Watts

Watts = V * Iin
Alternately P=I²R (P = I x I x Rm)
=======

I presume that Watts = U² / R ......... and if U is /2 , R must be /4 ( for "Watt" stay the same value )

Hi , if i want to "convert" my BLM ( wich is 2S configured ) in a 1S configuration , is it the good way if i give it ( my BLM ) the 1/4 of the original 2S config resistance ?

If it is made with 0.5 Ohms , does i give it 0.125 Ohms ( 2S => 1S ) ?

--------

Thanks to try to understand my translation

Ron van Sommeren · Aug 11, 2008, 01:37 PM

Motors are not resistors, they behave differently. You have to halve the number of winds. That will gave you the same rpm. No you have room for thicker wire, that's nice because motorcurrent has doubled.

barney 69 · Aug 12, 2008, 04:10 AM

Ok , thanks ........ the wire will give me a very low resistance but i must not "think to much" about the resistance .

I must "think only" about KV ( halve the number of turns and give the stator the "maximum of copper" , maximum thickness to the wire ) , and "to say to me" that the maximum thicker wire does not want to say bad efficiency for the motor .

It is true ???

Oct 24, 2006, 02:55 PM	#1
fly_boy99 Flying motor mount master Join Date: Oct 2004 Location: San Jose, California, United States Posts: 8,457	Motor formulas I thought it would be a good idea to have a sticky around motor formulas we constantly use here in the EMD&C section. If there is an error please PM me instead of posting here. Please add new formulas as you see fit but please do not clutter this stickey with commentary. If you wish to do that start your own thread. Thank you. ======= Efficiency Motor Efficiency = Pout/Pin Pout = (Vin - Iin * Rm) * (Iin - Io) ======= Motor Kv Kv = RPM / (Vin - Vloss) Vloss = Iin * Rm ======= Motor RPM RPM = Kv * (V - Vloss) Vloss = Iin * Rm ======= Watts Watts = V * Iin Alternately P=I²R (P = I x I x Rm) ======= Stalled Motor Istall = Vin / Rm ======= Torque constant Torque constant: Kt=Kb x 1.345 Kb = Voltage constant (Volt/1000 RPM) ======= Torque Loss Torque = Kt * (Iin - Io) ======= Termination Wye = the number of winds you have performed Delta = divide the number of turns by 1.73 ======= Watts per Horsepower 1 horsepower = 746 watts ======= Acronyms ======= Rm = Resistance value of the motor, derived from the guage of wire used Pout = Power Out of the Motor expressed in Watts Pin = Power In of the Motor expressed in Watts Vin = Voltage Into the Motor Iin = Current Into the Motor Io = Noload Current of the Motor, derived from running a motor WOT without a prop at varying voltages. Io can be expressed with an associated Voltage and should be. Kv = K value or voltage constant, the expressed value where the rpm can be surmised by a given voltage. For a 2000 Kv motor an input voltage of 10V would net 20000RPM. Istall = The load current of a motor which is purposely stalled, hence not turning Kt = Torque constant (oz-In/A) Kb = Voltage constant (Volt/1000 RPM) Note: Data has been gathered and utilized from various sources such as the aveox site as well as others. Last edited by fly_boy99; Mar 26, 2007 at 02:31 PM. Reason: Thanks Jeremey

Apr 13, 2007, 02:28 PM	#3
tomekr Registered User Join Date: Jun 2006 Location: Poland, near Warsaw Posts: 4	Max power (with akceptable efficiency) of the motor is about Pin[W]=1600Vmagnet[inch^3] Pin[W]=0.1Vmagnet[mm^3] This formula is based on practice, and work well on neodym magnet. It is very usefull to calculate an appropriate max. supply voltage, rpm, proppeler etc. (based on the motor resistance and expecting efficiency or simply optimal motor current) Last edited by tomekr; Apr 13, 2007 at 02:45 PM.

Sep 29, 2007, 09:12 AM	#6
flyman77 logicman Join Date: Sep 2007 Location: hemslingen germany Posts: 33	magnets and poles How does one calculate how many magnets to use against the number of poles, and what decides the winding direction? Anyone please? Thanks Brian

Oct 26, 2007, 01:47 PM	#7
heliovaitsman Registered User Join Date: Oct 2007 Posts: 3	Squematic Circuit Z3007-26 HypÉrion PLEASE SOMEBODY HAVE AN ELECTRIC CIRCUIT OF ELECTRIC MOTOR BRUSHLESS 12 POLES 14 MAGNETOS? THE MOTOR IS Z3007-26 HYPERION the bindings betweem wires are delta or star? TKS Hélio Vaitsman Last edited by heliovaitsman; Oct 29, 2007 at 06:49 PM. Reason: complete information

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
motor formulas	qwe123	Power Systems	6	Mar 23, 2004 02:52 AM

Oct 25, 2006, 06:57 PM	#2
Ron van Sommeren homo ludens modellisticus Join Date: Feb 2001 Location: near Nijmegen, Netherlands Posts: 8,674	Not exactly formulas: Doubling the number of winds halves Kv (rpm/volt) and doubles Kt (torque/Ampere) Doubling statorheight halves Kv, doubles Kt and (roughly) doubles maximum power.

May 12, 2007, 06:17 PM	#4
Fourdan Registered User Join Date: Sep 2003 Location: Antony (France) Posts: 1,513	About termination Kv ratio = 1.732 is a controversy A lot of testers found a ratio between 1.78 and 1.9 Louis

Sep 20, 2007, 05:05 PM	#5
marc780 Registered User Join Date: Sep 2007 Posts: 60	huh?

Dec 19, 2007, 06:51 AM	#11
Ron van Sommeren homo ludens modellisticus Join Date: Feb 2001 Location: near Nijmegen, Netherlands Posts: 8,674	I cannot help you with motor size, winding numbers etc. for your plane, for that you need input from people who have experience with those planes. Excellent motor building articles by Brian Mulder, a must read: http://www.southernsoaringclub.org.za/ -> Articles by SouthEasterners. -> Electric Motors - part 1-5 Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it: http://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of subforum) Vriendelijke groeten Ron van Sommeren • brushless motor building tips & tricks • diy brushless motor discussion group • Drive Calculator download & discussion group

Aug 11, 2008, 01:37 PM	#14
Ron van Sommeren homo ludens modellisticus Join Date: Feb 2001 Location: near Nijmegen, Netherlands Posts: 8,674	Motors are not resistors, they behave differently. You have to halve the number of winds. That will gave you the same rpm. No you have room for thicker wire, that's nice because motorcurrent has doubled.

Aug 12, 2008, 04:10 AM	#15
barney 69 Registered User Join Date: May 2007 Location: France neer Paris Posts: 264	Ok , thanks ........ the wire will give me a very low resistance but i must not "think to much" about the resistance . I must "think only" about KV ( halve the number of turns and give the stator the "maximum of copper" , maximum thickness to the wire ) , and "to say to me" that the maximum thicker wire does not want to say bad efficiency for the motor . It is true ???