ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The abstract presents two methods of solving induction motor problems using a time-harmonic approach, taking into account the saturation of the iron material. The first method uses the following algorithm. Initially, two static nonlinear problems are solved: one problem using the real part of the stator currents, and the other using the imaginary part. From both solutions, a reluctivity vector is generated. This reluctivity vector is then used in solving a time-harmonic problem to calculate the induced rotor currents. These currents are used to solve two new static problems. From the solution, a more accurate reluctivity vector can be generated. Convergence of this method occurs after 4 or 5 steps. The second method is an iterative method of solving nonlinear time-dependent problems by harmonic representation. It is assumed that H(t) is a sinusoidal function of time. A new sinusoidal Beq is introduced based on energy equivalence with the real nonsinusoidal B. This new Beq is used to calculate the new B-H curve for the iron materials involved and after that an equivalent reluctivity. The nonlinear algorithm represents under-relaxation of the equivalent reluctivity, based on the formula: RELUCTnew=RELUCTold+ALPHA*(RELUCTcrnt−RELUCTold), where ALPHA is a relaxation factor usually chosen between 0 and 1. The algorithm shows a good convergence rate (from 10 to 20 steps) if the initial starting vector for reluctivities and the relaxation factor are chosen appropriately. Rules for this choice are given. Both methods are compared. The difference between the induced currents in both methods is about 1%, with a linear solution it is about 300%. Also stored energy, losses, reluctivities, and other quantities are compared.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.355506
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