Abstract
The analytical method for the determination of the mechanical characteristics of the asynchronous motors by varying the electric current frequency is analyzed. Not only the current frequency but also the supply voltage of the motor is changed in the frequency converters used to regulate the rotation speed of the asynchronous electric drives by using particular speed regulation law. The presented analytical method for the determination of mechanical characteristics is based on the same Kloss formulas which are dedicated to calculate the relative magnitudes of the torques under respective slips in the starting and operational parts of the mechanical characteristics and under nominal supply voltage parameters of the asynchronous motors. All the magnitudes included in these Kloss formulas (coefficients, exponent indexes, relative magnitudes of the starting and breakdown torques) are recalculated according to the modified parameters of the supply voltage and after that according to them the new relative magnitudes of the torques are determined under the selected slips. Using these relative magnitudes the families of the speed regulation mechanical characteristics of the asynchronous motors are determined. Ill. 2, bibl. 5, tabl. 4 (in English; abstracts in English and Lithuanian). http://dx.doi.org/10.5755/j01.eee.112.6.433
Highlights
The electric drives are still one of the fastest developing areas of the science at the present time
When other values of the slip are present in the mechanical characteristic range of the locked-rotor, the relative magnitudes of the torques are calculated according to the following Kloss formula
In order to calculate the relative magnitudes of the asynchronous motor torques under different rotor slips, under current frequency f1 i ≠ f1n and supply voltage U1 i ≠ ≠ U1 n, the i-th speed of the rotating magnetic field is determined at first n1i 60 f1i / p
Summary
The electric drives are still one of the fastest developing areas of the science at the present time. When other values of the rotor slip are available in the operational range of the mechanical characteristic (0 < s < sc), the relative magnitudes of the torques are calculated according to the following Kloss formula. When other values of the slip are present in the mechanical characteristic range of the locked-rotor (sc < < s < 1), the relative magnitudes of the torques are calculated according to the following Kloss formula k2 s s k2. In order to calculate the relative magnitudes of the asynchronous motor torques under different rotor slips, under current frequency f1 i ≠ f1n and supply voltage U1 i ≠ ≠ U1 n , the i-th speed of the rotating magnetic field is determined at first n1i 60 f1i / p. On the base of the calculated magnitudes of the relative torques under different current frequencies and aupply voltages the family of mechanical characteristics of the asynchronous motor is created
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