SU796998A1 - Induction electric motor - Google Patents

Description

(54) ASYNCHRONOUS MOTOR

 .

The invention relates to an electric motor, and more specifically to a device of three-phase, asynchronous electric motors with a short-circuited or phase-wound rotor, having a starting torque value.

Three-phase asynchronous electric motors are known, containing a rotor and a stator fc with grooves made with a bevel (1.

The disadvantage of the known is the low value of the starting torque.

The closest in technical essence and the achieved result to the proposed is an asynchronous motor with magnetic conductors of the rotor and stator with grooves made with a relative partial bevel

12.

A disadvantage of the known is the lower values of the energy indices.

The purpose of the invention is to increase the energy performance of asynchronous electric motors.

This goal is achieved by the fact that the relative skew of the slots of the rotor and stator magnetic cores are Lc (0g002-0.014), in the 0.1-0.25 section of the length of the magnetic cores, where D is the diameter of the stator bore, p is the number of pole pairs.

Figure 1 shows a variant of the partial slope of the grooves in accordance with the invention; Fig. 2 shows the dependence of the ratio of the induction square of the net flux in the gap of the machine with slots with a bevel to the square of induction in a machine with straight grooves and the slope of the grooves in the start mode; in FIG. 3, the relationship of the ratio of square induction in the machine with bevelled and non-beveled grooves to the length of the bevel; figure 4 - the dependence of the slope of the slots from

the length of the magnetic circuit on which the grooves are made with a bevel.

A complex task is being solved - it is necessary not only to increase the value of the starting torque, but even with this, the level and efficiency should not be dispelled. Going beyond the upper limits of the ranges of change in b (especially

at small values (.) and I (especially at small values of Lc) leads in the zone of nominal slip to a rapid decrease in the resultant flow in the gap compared to the machine

Claims (2)

the main performance and, consequently, to a significant decrease in the efficiency of the machine. Justify the limit for the value of the slope bevel Lc; 0,0021tD | P. We will look for that zone of minimum values for which it is still theoretically possible to increase the starting torque without degrading the energy characteristics in the zone of nominal slip. In a well-known engine design, the following fact is used: in an asin background engine with a conventional groove slope, the resulting flow at the time of starting is much greater than that of an engine without groove slope. This allows the use of part of this excess flow in the engine of the proposed design to increase the starting torque. Consequently, it is necessary to find the minimum rational value of b to find those values of b. For which an increase in the flow in the gap of an engine with groove bevel can already be neglected. It should be noted that the moment of the asynchronous motor is proportional to the square of induction of the resultant flow in the gap. FIG. Figure 2 shows the dependence of the square of induction of the resultant flow in the gap of the machine with groove bevel (relative to the square of induction of the machine without groove slope) as a function of tof. for slip zones (i.e., for the start mode) for different machines having in the start mode the smallest shear angle of the magnetizing forces of the stator and rotor in and, therefore, most sensitive to changes in the spatial position of the MDS Fj vectors, the rotor windings. The entire power range of bipolar A2 series, AO2 series was investigated. From the data of FIG. 2, it follows / that for values of B.0.0021SH | The influence of the slope of the grooves on the amount of flow in the motor gap in the zone S "l can be neglected. Basically, this is due to the fact that asynchronous motors with only those with a starting torque 1.2-1.64 times more than the starting torque of the engine of the main execution are referred to the increased value of the starting torque. In order to get the engine starting torque more at least 1.2 times than the main one, it is necessary in the gap to have 1.2-1.4 more induction in the start mode than the main one. In this case, the transition from the usual bevel of the grooves to partial pr leads to a certain decrease in the flow in the gap. For these reasons, the value, 002 is chosen as the lower limit at which the gain stream can be neglected. In order to maximize the flow increment in the start-up zone, it is necessary to carry out a partial bevel at the upper limit of the coupling frequency of the magnetic circuit. Let us determine the minimum value tc.npH where the value of the square of the induction of the resultant flow in the gap can no longer provide the level required for a machine with an increased starting torque, Degree, determine the minimum value of If-, perform the analysis for the largest possible value of b. the nominal slip zone does not yet impair the energy performance of the machine. For this purpose, given the values at a constant value of t 0, 071tD | P, we will find an equivalent value of b. machines with a conventional groove bevel, after which we will determine, in view of the steel saturation, the induction of the net flow in the gap. The results of the analysis are presented in FIG. Comparing the data and conclusions made in Fig. 2, it can be concluded that the value, 052t:, should be considered as the limit, with the theoretical effect of increasing the starting torque. However, it is necessary to take into account here that for such a small length, it is necessary to realize the maximum value of Lp, which cannot but lead to a loss of efficiency in the area of the nominal load, due to a significant reduction in the cross section of the rotor winding rod, on the beveled portion and, resistance due to the implementation of a large bevel on a small length. Therefore, in this case, it is advisable for the rational limit t to choose the value at which the engine being developed cannot possibly be attributed to engines with a positive starting torque. As such a rational limit (; according to FIG. 3, a value should be chosen, l t. On the basis of the theoretical and experimental analysis, a relationship has been obtained that establishes a rational relationship between the values of b (. And 1 s necessary to obtain an electric motor with higher energy values). indicators (see Fig. 4). From the data of Fig. 4, it follows that for the limits of the ranges of variation of Gs, the cross dependence, i.e., the maximum value of B, corresponds to the minimum values and vice versa. Discovering Asynchronous motor comprising a stator yokes and rotor slots for windings, a partially relative bevel, characterized in that, in order to increase energy indicators bevel grooves bt value (0, p02-0,014) 1CD | P, is formed in the area 0.1-0.25 of the length of the magnetic cores, where D is the diameter of the bore of the stator, p is the number of pairs of poles. Sources of information taken into account in the examination. 1, Sergeev PS, and others. Designing electrical machines. M., Energie. 1969, p. 422-423. 2. Authors certificate of the USSR 655036, cl. H 02 K 17/02, 1976. is ± fS 0,001Q, OQfi 09.2 (g Vf .iwj V /