# matlab problem

• Oct 25th 2009, 12:17 PM
aabbddlah
matlab problem
Hello everyone

i v just joined the forum and i would like u to give me some sort of help in my induction motor project
i am using matlab to carry out the value for torque and then plot the torque Vs speed graph using matlab

so i am given the parameters
I2=5.42A
R2=.8Ω

to carry out the torque values for (rotor speeds(wr)=from 0-50rad/s)

and slip=1 when wr=0

Torque=(3/wr)*(I2^2) * {R2(1-s)/s}
To sum up i want to produce a torque speed plot using matlab

i suppose that i can do that using for loop
i think that it is not hard but i am not that good in matlab

here is my little attempt

for I2=5.42

for R2=.8
for s=.02
torque=(3/wr)*{(i2)^2}*{(r/s)*(1-s)}

plz help!
torqueplot
• Oct 25th 2009, 02:41 PM
elbarto
Try This:

Code:

```I2=5.42; R2=.8; s=.02; wr = 0:50; torque=(3./wr)*(I2^2)*(R2/s)*(1-s); plot(wr,torque) xlabel wr ylabel T title('Torque Plot')```
• Oct 25th 2009, 03:18 PM
aabbddlah
Well that was outstanding
many thanks to u sir(Clapping)
• Oct 25th 2009, 11:25 PM
elbarto
No problem at all. Please let me know if there is anything in the code that is unclear. I was in a hurry this morning so did not have time to add comments to help explain how plotting in MATLAB works.

Regards Elbarto
• Oct 26th 2009, 03:32 PM
aabbddlah

Sorry but I think that did not put the problem in the proper way
In fact torque should be calculated for different speeds and slips
(Not only different values of speed!)
So
given
R2=.8ohm
Rt=1.2ohm
Lt=2.2ohm
L2=3 ohm
s = (ws-wr) / ws , where ws=synchronous speed and wr=rotor speed
i2=formula in photo
torque=(3./wr)*(I2^2)*(R2/s)*(1-s
Also current cannot be one constant value
It should be calculated accordingly to slip values, so for each slip value we should have a value for current
To sum up , I think that we should use for loop to carry out values of slip ,corresponding speed ,and corresponding current on a range of values to create the proper plot
If the code is correct we must end up with the graph shown in the attachment
I will be thankful if u would help me
Many thanks
• Oct 26th 2009, 04:07 PM
elbarto
If you provide some code, even if it just a simple example calculation then someone will help you create the graph in MATLAB. I say this because it is difficult to understand the equations you posted up.

Also try to use code tags in your posts where appropriate. It makes reading code a lot easier.

Code:

`look for the # symbol on the toolbar`
Elbarto
• Oct 27th 2009, 11:50 AM
aabbddlah
elbarto
I do appreciate ur help

in the attachment there is a worked example to claculate the torque

so i want to plot the torque speed graph for different values of slip ,speed and current as well

• Oct 28th 2009, 07:09 AM
aabbddlah
hi
again

i think that i am nearly there

here is my attempt

vt=225;
rt=1.2;
f=50;
r2=.8;
ws=157;
Lt=2.2;
L2=3;
s=2:.001:-1.2;
wr=(1-s).*ws;
Z=sqrt(((rt+(r2./s))^2)+((Lt+L2)^2));
i2=vt/Z;
torque=(3./wr)*(i2^2)*(r2/s)*(1-s);
plot(s,torque);