Difference between simulation of electric machines form mathematical modeling and model used from simpower system tools

Why the mathematical modeling and simulation of electrical machines results are not equal results with machine model used form simpower system tool. I we used modeling of BLDC motor in mathematical equations in state space, transfer function and state equations methods. But the results are not exact equal from the motor model of simpower system tool. Simpower system tools model inside have state equations but they linking from supply is different. Power gui block will do the entire work. how we create our motor equation model to get near results without any simpower system blocks and power gui?