Rotor electrical frequency at no-load in induction machines simulated in FLUX 2D

Marco Biasion

Hello everyone,

I am simulating a four-pole induction machine in ideal no-load condition (slip s = 0) with a transient simulation in FLUX 2D. The supply frequency of the machine is fs = 50 Hz. The rotor rotates at synchronous speed, imposed in the mechanical set (ROTOR).
For the purposes of my analysis, I need to check the waveform of the magnetic flux density at some selected points on both the rotor and the stator core. I have been doing so using the sensors at different locations (teeth, yoke, etc).

Concerning the analyzed points in one period of the supply frequency T = 1/50 = 20 ms (let's assume in the stator and rotor teeth regions):

• In the stator teeth the fundamental frequency of the magnetic flux density B(t) is fs = 50 Hz + higher harmonics due to slotting effect, and this is very clear.
• In the rotor teeth, since s = 0 in ideal no-load condition, the fundamental rotor frequency is expected to be fr = s*fs = 0. So, I was expecting to see that B(t) was a DC component (rotor is magnetized) + higher harmonics due to slotting effect. However, B(t) has a fundamental frequency fr = 25 Hz. The reason is clear: B(t) is not displayed in the rotor coordinate system (which rotates at an electrical frequency of 25 Hz since I have a four pole machine), but in the stator coordinate system (fixed coordinate system). The same happens in case I export (on an Excel file) B(t) at the selected points in the domain.

From the physical point of view this is not correct.

I was wondering whether there may be a way to display/extract B(t) on the rotor referred to the actual rotor coordinate system (rotating system) in an attempt to overcome the issue mentioned above.

Thank you very much in advance.

Marco

Farid zidat_20516

Hello Marco;

 

Can you please select the mobile mechanical set in the management of the computation of the sensor ?

 

Normally if you do so, the flux density computed will behave as you said, DC componont + Slotting ondulation

 

Regards 

 

 

 

Marco Biasion

Farid zidat_20516 said:

Hello Marco;

 

Can you please select the mobile mechanical set in the management of the computation of the sensor ?

 

Normally if you do so, the flux density computed will behave as you said, DC componont + Slotting ondulation

 

Regards 

 

 

 

Dear Farid,

thank you for your answer.

I tried to do that but apparently in my simulation (2D) I can't select a mechanical set different than the STATOR: this means that I can only select a fixed mechanical set.

Unless I should set some parameters when defining the moving mechanical set prior to solving the simulation, I have no idea on how to overcome such issuse.

Regards,

Marco