Indirect torque measurement using industrial vector control frequency converter

This article deals with accuracy of indirect torque measurement of converter-fed induction motors. The measurement was held on both mid-(7,5 kW) and low-power (0,5 kW) motors supplied by Siemens SINAMICS G120 frequency converters. The vector control method was used, the effects of speed sensor presence or absence were evaluated. Also the motor temperature influence was taken into account and the proper converter commissioning and tuning were tested. The load torque was produced by dynamometer test bench with gauge strain measurement of force (torque) and the whole working area of tested drives was used. The evaluation of results shows that the relative accuracy of torque value provided by a converter is acceptable for particular industrial applications and allows to reduce expenses for direct torque measurement device.