SOME ASPECTS OF ASYNCHRONOUS MOTOR OPERATION WITH SECONDARY UNBALANCE

Abstract

The present dissertation analyses the behaviour of the Schrage motor under secondary circuit unbalance • The following different aspects of Schrage machine behaviour under secondary circuit unbalance have been inves tiga tech► S.) Operation of Schrage machine with unequal injected voltages ii) Operation of Schrage machine at synchronous speed which is a special case of secondary circuit unbalance • To put the study of unbalance case on sound footing, the steady state operation of the machine under balanced conditions of operation which is a prerequisite to the study of the machine under any abnormal conditions$ has been dealt with first and forms the very foundation of the proposed investigation • The study of machine under balanced conditions utilises the two axis acp*osch(c'gr axis or two axis-method) • The performance equations obtained involve machine parameters which are experimerr tally determinable • The method of symmetrical components, which is an invaluable tool for the study of almost all unbalanced cases, has been used to analyse the behaviour under secondary circuit unbalance -P an abnormal situation most likely to be met in practice. expressions for different sequence impedances Involved in the analysis have been derived strictly on the basis of physical interpretation and the contrasting study of the per-formance equations of the machine under balanced conditions • These sequence impedances are explicit functions of machine constants which are experimentally determinable and the slip. The performance equations derived are complicated mathematically and transcend the limit of detailed physical interpreation and usual computing methods • The modern technique of computing with the help of digital computers has been used to handle the calculation work • the study of torque due to zero sequence secondary . current has been made and the torque exprr anion has been derived taking into account the axis shift. Methods have been suggested to calculate the zero sequence parameters involved in final, torque expression, from the design data of the machine# as an alternative to actual cutting of the commutator winding at one point or at suitable points. The operation of schrage machine at synchronous speed is a special case of secondary circuit unbalance since secondary currents are direct currents and is an inherent one. Study has been made taking into account..