Parallel plate capacitor calculation is different in Maxwell & Q3D

- April 11, 2024 at 9:28 am
  
  Partho Bhoumik
  Subscriber
  
  Hi, I am new to the Ansys simulation environment. I was trying to verify the capacitor value calculation through Q3D extractor. I designed two 30mm x 30mm x 2mm plates with 1mm separation and calculated the capacitance using both Q3D and Maxwell3D. However, the Q3D value was higher (~10%) than the calculated value (using C = eA/d). But in Maxwell 3D, I got the exact value! Is this happening because of the fringing capacitance and if so, should the Maxwell 3D also consider that? Can somebody please explain this? I also noticed that if the A/d ratio is smaller in the design, the calculated value becomes higher than the theoretical value.
- April 19, 2024 at 2:29 am
  
  Howard Li
  Ansys Employee
  
  Hello Partho,
  When there is no air around geometry of Maxwell 3D model, we would get C values as same as calculated value. With air, we should have the fringing effect on the C calculation in Maxwell 3D simulation.
  HDLI