Motor modelling 1

[Kanu_01]

I have a motor of 44kW rating. I am choosing a typical data in SKM for my load(fan model) and motor model for TMS studies. And I could see an error of motor torque could be smaller than the load torque. What should I do to mitigate this error? I tried using different model, but still couldn’t mitigate the error.

 

[dpc]

Verify the load torque data is correct? If you are just using the "typical" library data in SKM, your results may not be that meaningful anyway. Especially for a non-NEMA rated motor.

 

[waross]

And I could see an error of motor torque could be smaller than the load torque.

Are you selecting the proper speed models?
Is this steady state or during starting?
You may have set a too short acceleration time.

 

[Gr8blu]

Motor torque performance (especially during transients such as acceleration) is carefully chosen against the required load torque for the process. There are multiple ways to change the shape of the motor's torque curve to better suit a specific load profile: the methods range from choosing a different material conductivity (i.e. rotor bar and/or ring) to modifying internal geometry (slot size/count, location and number of air ducts, radial air gap, etc.) to simply increasing the machine's steady-state power output (so that the per unit values for transient performance are based on a larger "base" number).

From the OP's description, it sounds like the "default" SKM design is a NEMA B, where the specific fan application (for whatever reason) needs something a bit more like a D.

The first step is to verify the actual fan load torque (curve) requirements. The second is to verify the motor torque performance.

 

[Kanu_01]

Motor torque performance (especially during transients such as acceleration) is carefully chosen against the required load torque for the process. There are multiple ways to change the shape of the motor's torque curve to better suit a specific load profile: the methods range from choosing a different material conductivity (i.e. rotor bar and/or ring) to modifying internal geometry (slot size/count, location and number of air ducts, radial air gap, etc.) to simply increasing the machine's steady-state power output (so that the per unit values for transient performance are based on a larger "base" number).

From the OP's description, it sounds like the "default" SKM design is a NEMA B, where the specific fan application (for whatever reason) needs something a bit more like a D.

The first step is to verify the actual fan load torque (curve) requirements. The second is to verify the motor torque performance.

Could you please specify some content that I could read to understand more about the curves to be used in accordance to load(as you mentioned fan requires NEMA D)? Thank you!

 

[waross]

Look at the speed/torque curve for your specific motor design.
Compare the motor speed/torque curve with the fan speed/torque curve.
The speed that fan torque curve rises to the motor torque curve will be the operating speed of the fan.
If this speed is below the rated speed then the motor will be overloaded.
As the motor comes up to speed, the difference between the torque demanded by the fan and the torque available from the motor will be the torque available for acceleration.

 

[Gr8blu]

First - understand what the torque curve for NEMA B vs NEMA D motors look like. Then look at some torque/speed curves for various fans. You might find that a high-inertia application (like an induced-draft fan) starts off requiring a lot of torque just to get the inertia moving - and then it usually takes a long time to get the fan wheel up to running speed. This means the motor has to deliver a different amount of torque at different per-unit speeds compared to say a typical ceiling fan.

You can find "typical" NEMA B and D curves in a consensus standard used by North American manufacturers: NEMA MG 1.
For other motors/manufacturers (including fan manufacturers) use the specific data available from them.

 

[DanielCooper]

Motor torque performance (especially during transients such as acceleration) is carefully chosen against the required load torque for the process. There are multiple ways to change the shape of the motor's torque curve to better suit a specific load profile: the methods range from choosing a different material conductivity (i.e. rotor bar and/or ring) to modifying internal geometry (slot size/count, location and number of air ducts, radial air gap, etc.) to simply increasing the machine's steady-state power output (so that the per unit values for transient performance are based on a larger "base" number).

From the OP's description, it sounds like the "default" SKM design is a NEMA B, where the specific fan application (for whatever reason) needs something a bit more like a D.

The first step is to verify the actual fan load torque (curve) requirements. The second is to verify the motor torque performance.


When modeling your 44kW motor in SKM, ensure that the motor's torque characteristics align with your fan load requirements. Discrepancies may arise from using generic library data. For precise modeling, consider sourcing detailed motor specifications from reliable suppliers like Ovaga Technologies. Their expertise in electronic components can provide the accurate data needed to enhance your simulation's fidelity.

Thank you so much for answering, you saved my day.

Edit: I also appreciate you for taking the time to write it in brief