Category, slot harmonics and the torque of induction machines

Abstract. Current spectrums of a four pole-pair, 400 kW induction machine were calculated for the cases of full symmetry and static eccentricity. The calculations involve integration of 93 electrical plus four mechanical ordinary differential equations. Electrical equations account for variable inductances affected by slotting and eccentricities. The calculations were followed by Fourier analysis of the stator currents in steady state operation. Zooms of the current spectrums, around the 50 Hz fundamental harmonic as well as of the main slot harmonic zone, were included.The spectrums included in this paper are referred to both calculated and measured currents.

Section: Full Symmetrymentioning

confidence: 99%

“…However, in the case of this machine, the amplitude of the twin harmonic tw is so small, that diagnosis of 60% static eccentricity is practically not possible. The frequency of the twin harmonic tw, to the left of the main slot harmonic, can be predicted by the following formula [8], [9]:…”

Section: Static Eccentricitymentioning

confidence: 99%

Diagnosis of Static Eccentricity in 400 kW Induction Machine Based on the Analysis of Stator Currents

Elawgali¹

2024

“…where f 1 = 50Hz, parameter h, following from (31) in [2], is h= 1, and the speed n rps = 24.705 rev./s. The discrepancy of 0.12Hz lies within the ∆f= 0.3815Hz frequency resolution.…”

Section: Direct Supply Centrically Aligned Rotormentioning

confidence: 99%

“…The discrepancy of 0.12Hz lies within the ∆f= 0.3815Hz frequency resolution. Justification for the presence of harmonic 1533.5Hz in Fig.1b is a (2) where the parameter β B results from (27) in [2]:…”

Section: Direct Supply Centrically Aligned Rotormentioning

confidence: 99%

Diagnostic information contained in inter-harmonics of a direct and PWM supplied induction machine

Rusek¹

2024

Self Cite

Abstract.The paper contains waveforms of currents for the direct and voltage source inverter supplied induction machine, with account for harmonics and inter-harmonics. By direct supply the grid is assumed to be polluted by 3 rd , 5 th and 7 th harmonics, normally present in real power supply systems. The voltage inverter was assumed to operate in a PWM mode, with perfectly constant DC link current. Spectrums of stator currents for direct supply create reference bases for spectrums by PWM supply. The model of the machine accounts for dependencies of stator and rotor inductances on rotor angle, resulting from winding and air gap geometry. Calculations of the derivatives of inductances, with respect to rotor angle, allowed for calculation of electromagnetic torque and machine's dynamics, with allowance for speed fluctuation, also in steady state operation.

“…The latter one falls out of our interest. The amplitude of the main slot harmonic is about -47 dB and its frequency can be predicted by the following formula [10], [11]:…”

Section: Healthy Machinementioning

confidence: 99%

Diagnosis of Mixed Eccentricity in 400 kW Induction Machine Based on Inspection of Stator Current Spectrums

Elawgali¹

2024

Abstract. This paper dealing with diagnosis of induction machines affected by combined eccentricity via analyzing the sator curents, inspection of the current spectrums and predict the harmonics that present in the spectrums and represent an indication for this ailment . The machine under invistigation is a 400 kW, four pole-pair, squarelcage induction machine. The current spectrums were calculated for the cases of full symmetry and mixed eccentricity. The calculations presented in this paper, are based on the poly-harmonic model that accounting for static and dynamic eccentricity, stator and rotor slotting, parallel branches as well as cage asymmetry. The calculations were followed by Fourier analysis of the stator currents in steady state operation. The inspection of the current spectrums focusing on two main zones these are the 50 Hz fundamental harmonic zone and the main slot harmonic zone. The paper will include the zooms of the above mentioned zones to demonstrate the harmonics presented in each zone.The calculated spectrums will be compared with the spectrums of the real measured currents.