Accuracy of COMSOL Unipolar Generator

Tesla Pratt, 6/18/24 — Professor Littman

Objective: Verify accuracy of COMSOL Unipolar Generator simulation using equations derived from Maxwell’s equation and the Lorentz Force equation  

Calculations: Following the process of Crooks et al. 1978 in this Crooks et al. 1978 paper, we can simplify the EMF calculation for a rotating disc with a uniform field to E = (1/2)(R^2)Bw. 

  1. Pulling values directly from COMSOL’s original Unipolar Generator Simulation, R=0.1m, B=1T, and w=125.7rad/s.
  2. E = (12)(0.12)(1)(125.7) = 0.628V
  3. Theoretical output voltage: 0.628V

Comparison:

  1. After plotting the electric potential of the generator in COMSOL, specifying the maximum and minimum voltage values, we get a maximum of 0.4V on the outside of the disc, and a minimum of -0.232V at the very center. The positive difference between these two values is 0.632V.
  2. Comsol Output Voltage: 0.632V
  3. With a theoretical value of 0.628V and an actual value of 0.632V, the result is a very low percent error of 0.637%.

Conclusion: We have verified that the COMSOL unipolar generator simulation produces believable Magnetic and Electric Field outputs.