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Computer calculations of pulsatory torques of three-phase induction motors for diagostics purposes

100%

Rawicki S. , Idziak P.

tom Nr 50

85-95

The paper deals with the problems of the mathematical modelling of the damaged three-phase induction motors. Analysis of internal asymmetries of the induction machine comprises the internal short-circuit, lack or inversion of a winding part and break in the parallel path of the winding. As a result of failures, pulsatory electromagnetic torques appear. At a defect in the stator winding, they have the double frequency in relation to the frequency of the supply network however for the damage in the rotor the frequency of the additional pulsatory torques is equal to double network frequency multiplied by the rotor slip. Existence of the pulsating torques can be treated as a diagnostic signal informing about appearance of the winding failures. This method can realize non-invasive diagnostics of induction motors. Calculations for the cases of internal asymmetries are simplified within the new modelling method by assumption of the equivalent structure of the damage induction machine with two parts: the symmetrical three-phase machine connected with additional electrical circuit.

Analiza akustycznego widma trójfazowego silnika indukcyjnego przy uszkodzeniach uzwojenia stojana

100%

Rawicki S. , Koczorowski J. , Nowak M. , Mirski R.

tom Nr 86

191-196

The paper concerns the diagnostics of windings defects in three-phase induction motors basing on the electric machine noise analysis. With the help of the computer software, the acoustic spectrum was analysed and the dominant diagnostic harmonics of noise of the three-phase slip-ring induction motor have been determined. The failures of the following type: the internal shorting between two phases and the short-circuit of the stator coil have been investigated. The problem of the increase of the damage degree was also analysed. Within the framework of the comparative diagnostic methodics, the properties and parameters of the symmetrical three-phase induction motor are the basis for a state valuation of the electrical machine. It was illustrated that the change of the acoustic spectrum can give information about the technical state of the motor. The interesting methodology of noise research consists in investigations for frequencies of a wide range. All presented in this paper measurements have been done for the three-phase induction slip-ring motor placed on the work-stand.

Porównanie napędów z silnikiem indukcyjnym dwufazowym i trójfazowym z litym rdzeniem wirnika

100%

Bogumił M.

tom Nr 86

95-100

The article presents researches results of one-phase drivers equipped with two- and three-phase induction cage motors with solid rotor core. The motors have been constructed on the base of typical three-phase induction cage motor with two-poles and shaft height 90 mm. Typical sliced core was removed from shaft and replaced with solid core. The solid rotor was tested in two- and three-phase stators of experimental motors powered from electronic inverter. There are presented comparative researches results of drivers at continuous work with decreased load due to highest temperature growth and torques characteristics at different frequency. All comparisons were preformed for several air gap value.

Eksploatacja i diagnostyka silników indukcyjnych trójfazowych klatkowych w przemyśle

100%

Szymaniec S.

tom Nr 84

127-132

Electric induction motors with squirrel-cage rotors are most widely used in the industry as electric machines driving other devices. This results from many reasons, among others, from their affordable price and fairly high reliability. The most popular are 6 kV motors, i.e. high-voltage motors that that drive the most important machine units. The article presents principles of operation of these motors in the industry and discusses methods of operation: - operation until failure occurrence, - planned and preventive operation, - operation dependent on a machine condition. The paper demonstrates conditions of appropriate motor operation in the industry. It also discusses the concept of “motor life” in industrial drives and types of their damages as well as damage statistics.