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Asynchronous machine incorrect speed plot

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Julio Incerti de Figueiredo
Answered: Graham Dudgeon on 27 Apr 2021
I have made a simple model for an Induction Motor. I've used its constants (stator's and rotor's impedance and resistance etc) that I've found at its datasheet. I was expecting to find its Nominal Speed (around 4400 rpm with 2 pairs of poles at 150Hz), but instead I find this strange plot. At the beginning, it seems like the speed is indeed around 4400, but it starts decreasing until it hits 0 and I cant understand why.
During the simulation shown at the photo I was using Rotor Type: Squirrel Cage, Reference Frame: Rotor and Mechanical Power (at "Load Flow") = 6000W
Steps that didn't solve the problem:
-Change the voltage between 51V, 51*sqrt(2)V and 51*sqrt(2)/sqrt(3)V
-Change the slip between 0.0267, 0 and 1
-Change the reference frame between Rotor, Stationary and Synchronous
-Add an input at Tm
-Change the solver information between ode15, ode23 and ode45
  1 Comment
Mike Sasena
Mike Sasena on 27 Apr 2021
Hi Julio,
It might help to update the tags in your question. The motor model you're showing is not part of Powertrain Blockset's library, but appears to be a Simscape model instead (this one?). I've added the Simscape Electrical tag so that team can better find your question and provide some guidance.

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Answers (1)

Graham Dudgeon
Graham Dudgeon on 27 Apr 2021
Hi Julio,
The speed reduces as you have a friction factor of 0.05479 on your motor shaft that is not compensated for by an input torque. Connect a constant block to 'Tm' and set the value to -150*2*pi*(1-0.0267)*0.05479/2.

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