Abstract
This paper has proposed and substantiated the application of an additional diagnostic parameter for assessing the state of stator windings of induction motors during operation. The dependences of the values of phase shifts between phase currents and phase voltages have been obtained. These dependences showed that when an inter-turn short circuit occurs in the stator windings, the phase shifts are the same for all phases of the motor. That has made it possible to obtain the dependence of the change in phase shift on the change in the engine shaft rotation frequency. This study's result has established the dependence of the rates of change of the phase angle on the engine shaft rotation frequency for both one and two damaged phases with varying degrees of damage. When analyzing these dependences, it was found that with an increase in the number of damaged phases of the electric motor, the linear section of the dependences decreases. In addition, with an increase in the degree of phase damage, the angle of inclination of the linear sections of the characteristics decreases. That has made it possible to determine an additional parameter for diagnosing the place and degree of an inter-turn short circuit of the windings in an induction motor with a squirrel-cage rotor. The values of the additional parameter, termed by this paper's authors as a "phase criterion" can be used to assess the condition and degree of damage to the stator winding of induction motors. The values of the phase criteria for various types of damage were: when phase A is damaged by 90 %, ξ=0.634, (deg)2/(rpm)2; when phase A is damaged by 80 %, ξ=0.393, (deg)2/(rpm)2; when phase A is damaged by 80 % and phase B is damaged by 90 %, ξ=0.25, (deg)2/(rpm)2; when phase A is damaged by 80 % and phase B is damaged by 90 %, ξ=0.173, (deg)2/(rpm)2. The results of this research could be used to select an effective method for diagnosing an inter-turn short circuit in the stator winding when building a diagnostic system for induction motors as part of drives of transport equipment
Highlights
For optimal and reliable operation of the transport infrastructure, it is crucial to maintain the operational condition of electric drives, which make up a significant part of the auxiliary equipment of transport systems [1]
We studied the influence of the degree of an inter-turn short circuit in the stator windings of the induction motor on its operating parameters based on its mathematical model, the equations of which are recorded in three-phase coordinates
The mathematical model of an induction motor with a squirrel-cage rotor, adopted for research, makes it possible to simulate inter-turn faults taking into consideration changes in the mutual inductance of stator windings
Summary
For optimal and reliable operation of the transport infrastructure, it is crucial to maintain the operational condition of electric drives, which make up a significant part of the auxiliary equipment of transport systems [1]. One of the hard-to-diagnose defects that cause the deviation of the engine parameters from the rated values and contributes to the transition from a gradual rejection to a sudden one is the inter-turn short circuit in the stator windings. With this defect, given a small number of squirrel-closed turns of the damaged phase of the winding, the induction motor may stay in working condition. With a further increase in the number of squirrel-closed turns in the winding phase, the electric motor enters an inoperable state due to the critically increased value of the phase current in the damaged phase [6]. It is a relevant task to identify additional diagnostic parameters when diagnosing an inter-turn short circuit in the stator windings of the induction motor
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