Hi, I want to calculate the circuit of thermal resistance of an induction electrical motor.
In some reference they draw circuit that shown resistance. like attached picture.
Now i have a question about it:
1- how many resistant must be consider in parts, like shaft, rotor, stator and ...
Thanks for your attention
Hello! The experience I have is based on thermal circuits calculating the elevation of temperatures in transformers. Regarding the calculation of thermal resistances, it is necessary to consider the three types of heat exchange:
- Conduction: Rcd=l/(k*S), where l is the length of the path that the heat will travel [m], k is the thermal conductivity of the material [W/(m*K)] and S is the section cross section available for heat to flow [m²];
- Convection: Rcv=1/(h*S), where h is the convection heat transfer coefficient [W/(m²*K)] and S is the cross section available for heat to flow [m²];
- Radiation: Rrd=1/(hr*S), where hr is the radiation heat transfer coefficient [W/(m²*K)] which is temperature dependent and it makes the circuit solution iterative and Sr is the radiant surface [m²].
As for the question regarding the number of resistances required, it is a question of discretization, the more resistances, the more precise, but the greater the effort of discretization and computation. I consider it a good approach to use the smallest number that one can intuitively be deduced with the circuit nodes arranged at the points where it is intended to know the temperature rise.
- Badges
- Science topic
- Similar topics
- Entomology
- Resistance