## 1 Introduction
Stator phase current and rotational speed of the motor shaft [3; 4] are the data signals in the design of both the vector control [8; 9; 10] and the DTC systems. Hence, current methods should underlie the operation of the diagnostic system. Paper [2] proposes a diagnostic system that allows the detection of asymmetric modes in the traction drive system with the asynchronous motor under the conditions of asymmetry of the feed voltage system. The operation of the system in steady-state mode is based on the Park's vector approach [57], and in the event of a variation of the load on the motor shaft, on the method of control of variation in phase shifts between stator currents and the corresponding phase voltages [58]. The paper [59] proposes a method of detection of asymmetric modes in the traction drive system that features a vector control system. In the papers referred to above, the diagnosis of the asymmetric modes is proposed under steady-state conditions without accounting for the operational factors discussed above. Consequently, the current task is to determine the diagnostic parameters that allow analysis of the presence of emergency asymmetric modes in the traction drive system, taking into account the operational factors causing asymmetric modes even in the normal mode of traction drive operation, and to build the operational diagnostic system on its basis. The solution of this task will allow detection of the appearance of asymmetric emergency modes in the traction drive system at an early stage of their occurrence, prevent their further development, and prevent the complete damage of the traction drive elements in which a defect causing the appearance of asymmetric modes has occurred. Studies [2; 57; 47] have shown that both asymmetry in the asynchronous motor windings and asymmetry in the supply system, as well as the simultaneous occurrence of asymmetry in both the motor windings and the supply system, cause the appearance of asymmetric modes in the traction drive system with the same diagnostic signs. Furthermore, the process of changes in the inverter supply voltage and motor shaft load caused by the operating factors of the electric vehicle discussed above is a stochastic perturbation of the traction drive control system [39; 40; 41]. These disturbances result in quasi-symmetric modes in the traction drive system caused by transients. The operation of the traction control system is also affected by changes in the parameters of its elements caused by changes in the temperature of the traction motor [60; 61] and the inverter [19; 20; 21]. Therefore, this study has been compared to previous studies by including more relevant parameters in the evaluation. In particular, the proposed work explains the operation of the DTC, and presents the results of the DTC simulation and study in Section 2, the analysis of the results obtained, the development of diagnostic criterion based on the analysis of the results obtained, and construction of the diagnostic in Section 3, discussion in Section 4, and conclusions in Section 5. Hence, determining the diagnostic parameter that allows the diagnosis of asymmetric emergency modes in the traction drive system, accounting for the operational factors causing the asymmetric modes even during normal operation of the traction drive, is a relevant task. Investigation of Influence of Operational Factors on Starting Characteristics of the Asynchronous Motor