Error analysis in improved motor control center method for stem thrust estimation of motor-operated valves in nuclear power plants

An error analysis for improved motor control center (MCC) method that estimates the stem thrust of motor-operated valve (MOV) is suggested in this work. This method focuses on providing an alternative means for the periodic performance verification test with relatively lower error than the conventional MCC-based method. For evaluating the overall error of the improved MCC method, the errors are classified into two categories: the biased error and the random error. The biased error consists of the mean of the relative error between measured and estimated torque and that of the stem factor. The random error comes from the statistical analysis of the measured torque, stem factor, and motor electric data. The experiment result shows that this method has a reasonably lower error than the MCC-based method. Therefore, this method can be applied to the periodic verification test of valves with relatively low margins.