Compensation for Supply and Motor Unbalances and Line Resistance for a DC Signal Injection-based Thermal Protection Method

摘要

Thermal protection is one of the most important aspects in an electric motor protection system. A dc signal injection-based stator winding temperature estimation technique has been proposed for soft-starter-connected electric motors by the authors. As a continuation of the previous work, this paper proposes a compensation approach for power supply unbalance, motor internal unbalance, and line resistance. The proposed method is validated from experimental results on a 7.5-hp TEFC induction motor under variable load levels with an unbalanced power supply. The stator winding temperature estimation error is within 10°C in face of power supply unbalance.