For maximization of efficiency of interior permanent magnet generators (IPMSG) and optimization of machine control correct parameters of the machine are needed. Parameters used in advanced control of the machine are stator resistance, magnetic flux linkage and inductances of d and q axes. Alongside them ohmic resistance that represents core losses can be employed to further increase efficiency of control. This work will focus on implementation of MRAS estimator that has adaptive models with and without taking into account core losses. Using Matlab Simulink simulations were conducted and comparison of estimators was made under change of current in d and q axis and different values of resistance that represents core losses. Results show that value of resistance that represents core losses influences estimated values of parameters and that it is beneficial to take into account core losses for efficient control of the machine.