Rotor parameter determination for the Brushless Doubly Fed (Induction) Machine (BDFM)

A procedure has been established for obtaining equivalent circuit parameters for the Brushless Doubly Fed Machine (BDFM), also known as the Brushless Doubly Fed Induction Machine (DFIM), by transforming a reduced coupled-circuit model into a sequence component form. This approach takes advantage of the model reduction procedure’s ability to reduce a complex rotor structure to a single equivalent loop without significant loss of accuracy. An alternative method based on winding factors has also been developed and includes coupling via harmonic fields. Parameters determined in both ways are in close agreement with those determined from Finite Element Analysis (FEA) and experimentally. The advantages of each method is discussed in the conclusion section. LIST OF SYMBOLS X1, X2, Xr indicating a stator 1, 2, or rotor quantity X p1, p2 stator winding pole pairs (principal fields) g effective air-gap l, d stack length, mean air-gap diameter ws slot mouth opening ωr rotor angular velocity R,C,N,Z fields of real and complex numbers, sets of natural numbers and integers diag(X1, X2, · · · ) Diagonal matrix with scalars or matrices X1, X2 etc. kw winding factor for a single loop in a nest Neff effective turns Zeff Impedance of individual rotor loop (Ω) nr rotor turns ratio