| 摘要 |
The invention relates to a method and an apparatus (2) for determining an operating state of a motor (4) which is connected to a rigid network (6) and has a rotation speed sensor. According to the invention, phase voltages (ul, u2, u3) of the rigid network (6) which are applied to the connecting terminals (L1, L2, L3) of the motor (4) are used to determine its frequency (fN) and amplitude (U1), a measured shaft rotation speed (n) and a number of pole pairs (p) of the motor (4) are used to determine the slip (s) of the motor (4) as a function of the determined network frequency (fn), and the mechanical shaft power (Pmech) is calculated as a function of this slip (s), of the determined amplitude (U1), of an internal voltage (U11) in the motor (4) and of motor-specific parameters (X1, X2, Xh, R2, R1, Rfe, sigma). A method which is independent of power is thus obtained for determining an operating state of a motor (4), without any need to detect the actual current value.
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