Thermal issues in the design of permanent magnet based electrical motors

QuickField simulation example

Dr. Jose Camino

36 poles brushless DC motor with NdFeB permanent magnets.

Problem Type
Plane-parallel problem of DC magnetics and heat transfer.

Geometry

Given

DC motor power P = 12 kW
Voltage U = 600 V;
Speed N_n = 200 rpm;
Torque M_n = 573 N·m;
Insulation class: f (155°C);
Steel power loss (50 Hz, 1.6 T) p_f = 5 W/kg;
Air temperature T = 40°C.

Task
Which temperature will afford the magnets under the following working conditions:
Cooling: natural / forced
Load: permanent / periodic (50%)

Results
Rotor final temperature.

One has to keep in mind the use of forced air circulation as a normal procedure. The controller could offer additional options to pose a limit to currents and/or temperatures.

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