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Title: Smart motor protection
Author: Inuwa, A. D.
Awarding Body: University of Sussex
Current Institution: University of Sussex
Date of Award: 1992
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The temperature of the stator winding of an induction motor is monitored by measuring the resistance of the winding while the motor is in operation. By computer simulation of an induction motor controlled by thyristor phase control, using back to back connected thyristors in each phase of a 3 phase system. it is shown that the motor stator winding resistance can be deduced from the DC components of the phase voltage and current resulting from intentionally unbalancing the non-conducting periods (notches) in the voltage waveform. The DC voltage and current components are measured by integrating the unbalanced phase voltage and current over an exact number of electrical cycles. The stator winding resistance is determined by dividing the DC voltage component with the DC current component. A generalised d-q axes mathematical model of the induction motor system has been developed for the computer simulation. The practical implementation of the method using a phase controlled microprocessor motor controller and support circuitry is presented. A motor protection algorithm calculates the stator winding temperature from the measured stator resistance. displays the winding temperature and provides a motor protection function by comparing the calculated winding temperature with the temperature limit of the motor and acting accordingly. A calibration procedure before installation measures the motor stator winding resistance at cold and reads the motor's cold temperature. full load current and insulation class. Experimental results are presented and the features and the limitations of the method are discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available