## On the efficiency factor for induction motor at non-sine supply

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Authors:

Yu.V.Kovalova, Cand. Sc. (Tech.), orcid.org/0000-0002-2931-9176, O.M.Beketov National University of Urban Economy in Kharkiv, Kharkiv, Ukraine, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

```Naukovyi Visnyk Natsionalnoho Hirnychoho Universytetu. 2020, (1):64-68
https://doi.org/10.33271/nvngu/2020-1/064```

Abstract:

Purpose. Getting an analytical expression for calculating the efficiency factor for the induction motor with sine supply when connecting it to semiconductor converters of voltage or frequency. The task involves determination of influence of the harmonic components of the stator current on the efficiency factor for motor.

Methodology. The method for determining efficiency factor is based on the laws of energy conservation, Ampere, Kirchhoff and Faraday, the method of harmonic analysis, the principle of superposition for instantaneous power and the methods of the theory of electric machines.

Findings. The equation of the electric power balance is obtained for the harmonic components of the power of an induction motor with its non-sinusoidal power supply. An analytical expression is obtained for determining the efficiency of an induction sine-wave motor when connected to semi-conductor converters of voltage or frequency. An example of calculating the efficiency factor for induction motor of sine supply and the coefficient of its use when connected to a thyristor converter of voltage is given.

Originality. The power balance equation for an induction motor for harmonic components of current is further developed. Unlike the known ones, it takes into account the mechanical component of power. For the first time, the concept of the brake harmonic coefficient was introduced as the ratio of the sum of the effective values of the harmonics of the stator current inverse and zero sequence to the actual value of non-sinusoidal currents, which allows a quantitative estimate of the efficiency reduction. The analytical expression for determination the motor efficiency when supplied by converters of voltage or frequency has been improved.

Practical value. Analytical expression for determining the efficiency of an induction motor of sine supply when connected to semiconductor converters of voltage or frequency allows calculating the factor of using of motor of mechanical power, taking into account the permissible heating by non-sine current.

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