Rotor position detection in an electrical machine

An electrical machine has a rotor position transducer which provides output signals to a control system. The output signals contain errors due to component shortcomings and manufacturing imperfections. A method is disclosed which is able to determine the errors in the signals by successively running the machine with a series of assumed errors in the rpt signals and building up a set of test results. These results are subsequently compared with each other so as to determine the optimum value of corrections to the control system of the machine. The correction may be stored in the control system and used to improve the accuracy of the transducer output signals, thus improving the output of the machine.