Matlab Simulation of AC motor

[zolka]

Helo everybody!

I,m running a simulation of a 3 phase, squirrel-cage, wye-connected 7,5KW, 6 pole AC motor in MATLAB!
The simulation results are the next (direct on line starting):

1. starting current 170A, then after a few seconds when the motor reaches the rated angular velocity of 120rad/sec the current drops to 70A,
2. the minimum torque on the torque curve is 10Nm, the breakdown torque is 70Nm


I would like to know, if these results are possible???
I think the torque should be more than that!?
Please comment on the results!

 

[electricpete]

voltage? frequency?

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[electricpete]

Rated torque of this machine would be
T = Pe / (2 * Pi * f) ~ Pmech / (2*pi*f*efficiency)

Let's say 60hz power supply. f~20hz
T = 7500 watts / (2 * Pi * 20 hz * 0.9)~ 66 N
(double check my math).

I would expect typical breakdown torque somewhere around 2 - 2.5 * rated torque. 70N doesn't sound high enough at first glance

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[itsmoked]

Starting current seems low too.

170/70 = 2.4

Keith Cress
kcress -

http://www.flaminsystems.com

 

[zolka]

Sorry, I forgot the voltage and the frequency!
U=220v
f=60Hz