Modeling universal motor using FEM and simulink

[Graape]

I am supposed to reduce noise radiated from a 110V/60Hz Universal machine by driving it with a PWM controller instead of a simple Triac. The machine is used at relatively high torque which makes it always run in saturation. This makes the machine highly non-linear. Firstly I want to create a good model of the machine, at least in the non-linear region. I am using simulink and have an idea using a FEM program (FLUX2D) to (somehow) make a s-function simulink block which calculates machine parameters for each time-step. I´ve heard it is possible to make simulink-blocks from FLUX. Is this correct? In that case, does anyone have any experience from this? Every idea of modeling non-linearities will be helpful even if it doesn´t involve FEM.

 

[coconutalley]

I have done MW size drive and motor modeling using Matlab simulink. But, for $2k more you can get the Simpowersystems tool box add-on and that has a lot of motor models already created. The simpowersystem tool box from Mathworks is a circuit based model and interfaces with the simulink block. It was developed by an utility company in Quebec for Power systems and power electronics. Saved me a lot of time. It is still flexible enough that you can create your own models. I had to create an open-delta motor model using sources, RLC components, and simulink blocks because they did not have open multiphase delta type motors. Simulink can co-simulate with other programs but we ran into a lot of difficulties and tends to be real slow.

 

[Graape]

Thanks!
I have the simpower toolbox installed already, but the main problem consists. This motor is running very saturated and I don´t think the DC motor block in the simpower tool box will handle the saturation. Am I wrong? By the way, the machine have an input power rating of 550W and runs in the speed range 6000-12000rpm, depending on the application.

 

[coconutalley]

If the machine is saturating then this is not good. It is not good to run in saturation. Perhaps you need a higher hp machine? Does the app need that high rpm?
If you know the equations for the non-linearities, you should be able to include it a simulink block. You can create a motor model using the RLC and source components with Simulink blocks.
For example (if I recalled correctly) DC brushless pm 3 phase, one phase would use the ac source series with
resistor and inductor. You'd add a current meter in series to measure current and a voltmeter across the winding (RL) to measure your voltage. There is an input drive signal to the ac (bemf) source where you add the simulink signal to drive the source. You can feed this any waveform shape that you want. You can sum the currents x voltage to get power.
To get electromagnetic torque, use the differential equations in the Simpowersystems manual. Then you can get the speed = power / torque. This speed is your electrical speed. Divide by number of poles and that is your rotor speed. You integrate this speed twice to get your angle. This angle is used to produce 3 references phased 120 degrees apart to drive each input of the emf sources in your motor phase models. If you know what the bemf waveform looks like you can produce this and feed it to the ac input of the bemf sources. There is a book by Ong called "Dynamic Simulation of Electric Machinery using Matlab Simulink," I recommend this.
On the noise reduction, are you talking harmonic distortion?
If you want little or less harmonic distortion then you'd need a drive that produces sinusoidal current. What is a universial motor anyway?