THERMAL ANALYSIS UNDER FLUXMOTOR

NASSIM

Hi everyone,

I've started recently to work under Fluxmotor and particularly on the thermal analysis of pm machines.

I've some issues to understand the obtained results. In fact, the machine i studied is a classical in-runner pm machine with a natural convection cooling. i've launched a steady state simulation and i introduced only copper losses (280W @750rpm). The obtained result is a winding temperature of 200°C.

The strange thing is that when i try to re-calculate the temperature from the thermal resistances given by the software i get a much higher temperature

what i did is : thermal overheating is almost equal to 280*( slot_tooth_res//slot_yoke_res+(frame_straign_conv//cs_end_cap//ocs_end_cap) = 280*(0.1+0.98)=303°C which is the thermal overheating very big than the displayed value

can anyone please tell me what's is going wrong ?

Best regards

NewMotor1.zip

Ovando_RBB

Hi there,

I'm not entirely sure about the architecture of the steady state equivalent thermal resistance circuit you're using to model your application. However, regardless of the specific configuration, it's important to include the convective thermal resistance component referenced to the ambient mass temperature. This can be expressed as R=1/(h*S) where h is the heat transfer coefficient and S is the total area exposed to the convective movement of the air. That resistance is essential to accurately account for thermal compensation at each internal thermal node due to convective effects.

Additionally, I noticed that your setup uses a heat transfer coefficient of 8 W/(m²·K). This value appears quite low, specially if you're modeling the overall heat transfer experienced by the assembly with a moving rotor. A more realistic value would typically be around 25 W/(m²·K), and in cases with high rotor speeds, it could even reach up to 250 W/(m²·K). The exact value will depend heavily on rotor velocity and the nature of the surrounding airflow.

Hope these comments help!