Patent ID: 8362738

Claim:
A frequency converter, comprising: a load bridge; a control for the load bridge, for supplying electricity between the load bridge and an electric machine connected to the load bridge; a determination for at least one electrical parameter of the electric machine; and a determination for the position of the rotor of the electric machine, wherein a load bridge is fitted to supply a first alternating electricity excitation signal to the electric machine, which first alternating electricity excitation signal is formed in relation to the electrical angle of the electric machine, and the frequency converter is fitted to determine a first alternating electricity response signal corresponding to the first alternating electricity excitation signal, and the position of the rotor is determined on the basis of the first alternating electricity response signal and determined in an operating status in which movement of the rotor is prevented, wherein the load bridge is fitted to supply a pulse-like electrical excitation signal with the determined values of the electrical angle of the electric machine to the electrical machine, and the frequency converter is fitted to determine a plurality of pulse-like electrical response signals corresponding to the pulse-like electrical excitation signals; and the frequency converter is further fitted to determine a reference point for the position of the rotor of the electric machine on the basis of the pulse-like electrical response signals; and the load bridge is fitted to supply a second alternating electricity excitation signal to the electric machine; which second alternating electricity excitation signal is formed in relation to the electrical angle of the electric machine; and the phase shift of the second alternating electricity response signal corresponding to the second alternating electricity excitation signal is determined on the basis of the reference point of the position of the rotor of the electric machine and also on the basis of the second alternating electricity response signal.