Universal constant WL

for all Torquemax motors

 

Please read first How many windings does my LRK350-20 motor need?

Basics:

given measured values:

Um - motor voltage

Im - motor current

n - prop revolution per minute

Io - idle current

Ri - inner resistance

The actual effective working voltage is:

U = Um - Im * Ri

The revolution per volt:

ns(Im) = n / U

presents linear function:

ns(Im) = no + kns * Im

This linear function goes through y-axis at:

no=ns(0)

The product of no=ns(0) and windings number N is constant for any given motor independent of winding and wire size.

 

 no * N = W = constant

 

I have calculated this constant W for few motors with different stator lengths. Thank you to all friends for giving me some measurements on their motors.

There is long measurement behind each line in this table, that you can see as Excel table and diagrams.

Motor sheet D N Ri no kns W Stator-L WL
mm mm tooth Ohm no*L mm W*L
Peter/Jochen LRK350-20-11 0,5 35 11 0,016 852 -4,0 9372 20 187440
Peter/Jochen LRK350-20-13 0,5 35 13 0,024 761 -4,0 9893 20 197860
Peter/Jochen LRK350-20-15 0,5 35 15 0,036 630 -4,3 9450 20 189000
Oscar Leoni LRK345-24-12 0,35 34,5 12 0,019 706 -2,6 8472 24 203328
Dieter Doerr LRK345-12-19 0,35 34,5 19 0,037 867 -4,9 16473 12 197676
Jan Colberg LRK345-24-19,5 0,35 34,5 19,5 0,043 440 -2,1 8580 24 205920
Jan Colberg LRK345-24-12 0,35 34,5 12 0,02 706 -2,6 8472 24 203328

This table with motors of different stator lengths of 12, 20, 24 mm, but the same diameter of 35mm proves that there is a single constant number that specifies the whole family of motors, independent of

- stator length L

- windings number N

- wire size.

 no * N * L = W * L = constant = 200,000

 

Having this constant of around 200,000 you can always calculate the specific revolution per volt for any given motor.

 

Result:

you can calculate W-constant for ant stator length

W = 200,000 / L

then with how many windings does my motor need? the complete motor.

 

Calculation example

You have stator sheets with diameter of 34.5 mm and you wish to build motor. At your power you wish 20 mm stator length. The W constant is then:

W=200.000/20=10.000

then with how many windings does my motor need? you design the whole motor.

 

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