IRON LOSS IN ROTOR-FLUX-ORIENTED INDUCTION MACHINES - IDENTIFICATION,ASSESSMENT OF DETUNING, AND COMPENSATION

Iron loss, traditionally ignored in vector control schemes, has recent ly attracted more attention as a cause of detuned operation of rotor-f lux-oriented induction machines, Appropriate mathematical tools, that enable evaluation of detuning due to iron loss, have become available, and these have been used so far only in assessment of detuning for ra ted speed operation in the constant flux region, The available studies are based on the measurement of iron losses with voltage supply of ra ted frequency, This paper attempts to provide a more detailed treatmen t of iron loss induced detuning in rotor-flax-oriented induction machi nes by presenting at first an experimental method of iron loss identif ication over the entire frequency (speed) range of interest, The exper imental results enable calculation of the equivalent iron loss resista nce that is subsequently used in evaluation of detuning, The regimes d ealt with encompass motoring and braking operation in the base speed r ange and motoring in the held-weakening region up to the five times ra ted speed, It is shown that detuning in the base speed range will be t he highest at rated speed operation and will exhibit opposite trends i n motoring and braking regions, Detuning in the field-weakening region is found to be significantly in excess of the one at rated speed, pro vided that the machine operates at high speeds with relatively light l oads, As compensation of iron loss seems to be necessary in this case, the concluding part of tile paper presents a novel rotor flux estimat or that utilizes experimentally identified equivalent iron loss resist ance values and enables elimination of detuning that is otherwise pres ent. The estimator is a modified version of the well-known scheme that operates on the basis of measurement of stator currents and rotor spe ed (position), Its ability to compensate for iron lass is verified by simulation.