22 Electric Motors Fig. 1.14 Principal motor current and torque characteristics The motor operating range (0 • Starting range (0 B /n0 ) • Operating range (n B /n0 These ranges have the following characteristics: Starting torque Ta. This is the torque the motor produces with the rated voltage and rated frequency applied at standstill. Stall torque T B at stall speed n B . This is the highest torque the motor can produce when the rated voltage and rated frequency are applied. Rated motor torque T n at nominal speed n n . The rated values of the motor are the mechanical and electrical values for which the motor was designed in accordance with the IEC 60034 standard.
The rated values, also called motor specifi cations or motor ratings, are stated on the motor nameplate. The rated values indicate the optimal operating point for the motor, when connected directly to the mains.