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§elf Excitation in induction machine depends on appropriate combination of speed, load and excitation capacitance. This paper presents direct methods derived from Loop and Nodal analysis to find different criteria of maintaining self excitation. Unlike available techniques, the inverse-r model for the steady state equivalent circuit has been used. This is found to be of much assistance in the analysis. Besides determination of speed limits for fixed terminal parameters, and capacitance requirement under varying speed and load, a method to test the possibility of self excitation for known speed, load and terminal capacitance has also been presented.In a stand alone induction generator the major problem is that of guaranteeing self excitation. Self excitation of an induction machine and its sustenance depend on the appropriate combination of speed, load and terminal capacitance in relation to the magnetic non-linearity of the machine. These in turn cause certain limitations on the performance of the machine. In view of these, studies on the criteria for self excitation of an induction generator are considered to have practical significance.The excitation requirements, of an induction generator have been dealt with extensively in the literature [1--91. 'These studies have mainly given emphasis on the methods (direct or indirect) to obtain minimum capacitance values for sustained self excitation. Crantham et a1 [ 7 1 and Tandon et a1 [ 5 1 studied the onset of self excitation and minimum capacitance requirements based on the characteristic polynomial obtained from transient representation of the machine. This method requires sets of results, obtained from the numerical solution to the characteristic polynomial satisfying certain criteria, before inferring on the minimum capacitance at which self excitation occurs for a particular speed and load. Malik and Mazi[31 suggested an indirect procedure, based on the steady state equivalent circuit model, to test the self-excitation of an induction generator.The indirect methods involve solutions requiring some initial guess in a trial and error procedure.Al-Jabri and Alolah I81 and Chan [91 present direct methods t o test the self-excitation of an induction generator and compute the minimum capacitance for self-excitation. However, without detailed computation, both the methods do not suggest any criterion to test the self-excitation for any combination of speed, load and excitation capacitor, and also do not present the cut-off speed for given terminal parameters, viz. load and excitation capacitor, though an expression for a threshold speed Department of Electrical Engg. Indian Institute of TechnologyKharagpur 721302 INDIA is given, below whick-the generator fails to excite irrespective of the value of capacitance used.[IO] dealt with different phase steady state T-formIn a different pub1 Alolah on per OBJECTIVESThis paper re-examines the self-excitation requirements and in the process presents, in a direct way, various criteria that have to be satisfied to initiate voltag...