FR2462807A1 - Pole-changing motor winding - has two layers with three strands of coil groups maintaining constant torque - Google Patents

Abstract

The three-strand twin layer winding of motors for speed changing by altering the number of poles ensures maintenance of the torque. The design results in a high winding factor so that the generated flux can provide an increased power per unit of weight of the motor. Each group of coils is subdivided in both strands to form symmetrical combinations to decrease the circulation currents which are determined by the equivalent e.m.f. derived from phase vectors of voltages.

Description

 The invention relates to winding diagrams of alternating current electric motors and, more specifically, relates to three-phase two-layer windings with switchable poles for two-speed electric motors.

 The invention can be used in three-phase two-speed electric motors having speed regulation by jumps, the motor torque being constant.

 The invention finds its most advantageous application in the manufacture of two-speed asynchronous electric motors, since in this case the design and the technique of manufacturing a cage rotor and a non-stable stator can be totally retained. wound asynchronous basic electric motors at a speed manufactured in series.

A three-phase winding with two layers with switchable poles is known (see USSR author's certificate, No. 3999969) having coils distributed irregularly in groups, this winding being intended to be housed in 54 stator slots and having a ratio of numbers of poles
2p1: 2P2 = 8: 6 (I) P1 is the number of pairs of poles corresponding to the lower speed of rotation P2 is the number of pairs of poles corresponding to the speed of higher rotation.

 This indicated winding has an unsatisfactory harmonic composition of the magnetizing forces in the case of operation with a number of poles 2p = 6, which does not make it possible to start the motors at the higher speed of rotation if these are carried out at base of series rotor asynchronous motors with cage rotor speed.

The starting characteristics can only be improved by modifying the construction of a cage rotor: choice of another number of notches, use of a rotor with deep notches or a rotor with two cages, etc. which considerably complicates the technique of manufacturing two-speed electric motors and increases their manufacturing cost.

 In addition, the winding examined has a drawback specific to all switchable pole windings in which a change of direction of the current occurs in the half-phases when they are switched according to the diagrams or y where / YY y y. This drawback consists in the fact that it proves necessary to increase the number of contacts of the switching devices compared to the number of contacts essential for the change of the number of poles in two-speed electric motors with two separate windings on the stator.

 In three-phase windings with switchable poles which are switched according to the diagrams Y / YY and S / YY, a switching device comprising 8 pairs of contacts must be used to change the number of poles, while changing the number of poles in two-speed weld motors with two separate windings on the stator are carried out by means of two three-pole switches as standard, that is to say with 6 pairs of contacts.

 Thus, when replacing a two-speed electric motor with two separate windings on the stator by an electric motor with a switchable pole winding which is switched according to the diagrams or / yY, the number of contacts increases from 6 to 8, which lowers the operating reliability of the electric motor and increases the operating costs.

 The drawback mentioned does not exist in the three-phase two-layer winding with switchable poles switched according to the schemeYYy / uYY with coils distributed irregularly in groups according to the numerical series 2,2,4,2,4,2 , 2,2,2,4,2,4,2,2,2,2,4,2,4,2,2,2 and intended to be accommodated in 54 stator notches with a ratio of the numbers of poles 2pl: 2p2 = 8: 6.

 In this winding, as in any three-phase winding with switchable poles switched according to the YYY / Yyy scheme, the coil groups are divided into nine branches of the circuit. The windings have 6 terminals and have independent inputs when operating at any of the two numbers of poles. I1 shows that the number of poles in these windings is changed by the same switching devices and with the same number of pairs of contacts (6) as in the case of two-speed electric motors with two separate windings on the stator.

A peculiarity of the switched windings according to the scheme Y YY / YYY is the presence of three parallel branches in each phase (a = 3) for any of two modes of supply. I1 follows that on the appearance of a magnetic field with a number of poles which is not a multiple of 3, the known condition of symmetry of the alternating current windings is not respected and the ratio P n is not equal to an integer. It follows that the
a f.é.m. parallel branches of each phase of the winding prove to be unequal with respect to each other both in value and in phase.

où
E1, E2, E3 sont les vecteurs des f.é.m. des branches 1,2,3, de chacune des phases respectivement . La multiplication des vecteurs E2, E3 par l'opérateur "a" correspond à la rotation de ceux-ci d'un angle de 1200 dans le sens horaire, tandis que la multiplication de ces mêmes vecteurs par l'opérateur "a2" correspond à une rotation de 2400 dans le même sens. Since the vectors E1, E2, E3 of the f.é.m. parallel branches of each phase form asymmetric systems, any system of this type can be broken down into zero sequence components Eo, direct Ed and inverse Ein:

or
E1, E2, E3 are the vectors of the f.é.m. branches 1,2,3, of each of the phases respectively. The multiplication of vectors E2, E3 by the operator "a" corresponds to the rotation of these by an angle of 1200 clockwise, while the multiplication of these same vectors by the operator "a2" corresponds to a rotation of 2400 in the same direction.

The f.é.m. E balances the applied voltage and deter
o
mine in concert with it the value of the service current
I of the winding.

o
The f.é.m. Ed and E. only appear in the presence of a
in
of an inequality of the vectors EI, E2, E3, in other words in
presence of a potential difference between the ends
open parallel branches of the phases, and that's why
they are named f.é.m. differentials. Under the effect of
f.é.m. differential, equalizing currents I 'cross the branches of the winding which form short circuits
circuited, said currents ensuring no useful work and
causing additional electrical losses in
winding as well as high noise and vibration.

 The magnitude of the equalizing current can be approximated by the relative value of an emf.

I où: Eo, Ed, Ein sont les modules des vecteurs Eo, Ed, Ein.differential Equivalents aE * determined according to the expression:

I where: Eo, Ed, Ein are the modules of the vectors Eo, Ed, Ein.

in
In medium power electric motors,
this quantity must not exceed 0.02-0.03, otherwise the
indices of the electric motor such as efficiency and
vibroacoustic characteristics exceed the limits
admissible in the case of operation with a number of
non-multiple poles of 3. At the same time, the reliability of
the electric motor decreases.

For the winding described, the relative magnitude of
the f.é.m. equivalent differential is 0.043.

In addition, the winding examined, its pitch being y = 7,
is characterized by the following winding coefficients
= 0.817, Kw3 0.888 and Kwo = 0.8525,
where Kw4 is the winding coefficient in operation with
a number of poles 2pI = 8
Kw3 is the winding coefficient in operation with
a number of poles 2p2 = 6
Kwo is the mean winding coefficient equal to

 In the case of the switching scheme γ γ γ / γ γ γ the indicated values of the coefficients of winding do not ensure a ratio of values of magnetic induction close to 1 in the air gap, which is the necessary condition for the normal operation of an electric motor with speed regulation by hops or jumps , the engine torque being constant.

où
B8 (6) est l'induction dans l'entrefer lors du fonctionnement du moteur électrique avec un nombre de pôles 2pl=8(2p2=6);
B8(6) est la f.é.m. induite dans l'enroulement par le flux magnétique principal lors du fonctionnement du moteur électrique avec un nombre de pôles 2pl=8 (2p2=6)
W8(6) est le nombre de spires mises en série dans la phase de l'enroulement quand celui-ci est connecté pour le fonctionnement avec un nombre de pôles 2pI=8 (2p2=6).Indeed

or
B8 (6) is the induction in the air gap during the operation of the electric motor with a number of poles 2pl = 8 (2p2 = 6);
B8 (6) is the f.é.m. induced in the winding by the main magnetic flux during the operation of the electric motor with a number of poles 2pl = 8 (2p2 = 6)
W8 (6) is the number of turns connected in series in the winding phase when it is connected for operation with a number of poles 2pI = 8 (2p2 = 6).

Since with the switching of the winding according to the schemeYYYjYYY, E8xg E6 and W8 = W6, we have for the winding examined

 The invention aims to develop a three-phase winding with two layers with switchable poles for a two-speed electric motor, which has a distribution of the coils in groups and in branches according to the Y yY / YYY scheme such that it ensures coefficients winding values and a reduced relative value of the f.é.m. equivalent differential, which makes it possible to produce, from electric motors at a speed produced in series, electric motors at two speeds whose power per unit mass and reliability are higher and whose vibro-acoustic characteristics are improved .

 This object is achieved by means of a three-phase winding with two layers with switchable poles having 6 terminals and comprising fifty four coils which ', with a ratio of the numbers of poles 2pl: 2p2 = 8: 2, are distributed irregularly into groups of coils forming phases each having three parallel branches during operation at any number of poles, winding in which, according to the invention, the coils are divided into thirty three groups of coils, the number of coils in each group of coils, starting from the first, being determined according to the numerical series 3,2,3, I, I, 2, I, I, 2-, I, I, 3,2,3, I, I, 2, I, I , Z, 1,1,3,2,3,1,1,2, 1,1,2,1,1, the first, the fourth, the tenth, the twenty-ninth group of coils being connected to the first branch of the first phase, the sixteenth, the twenty-second, the twenty-fifth and the thirtieth groups of coils being branched to the second branch of the first phase, the ninth, the thirteenth and the seventeenth group of coils being connected to the third branch of the first phase, the seventh, twelfth, fifteenth and twenty-first groups of coils being connected to the first branch of the second phase, the third, the eighth, the twenty- seventh, the thirty third group of coils being connected to the second, while the twentieth, twenty-fourth and twenty-eighth group of coils are connected to the third branch of the second phase, the first branch of the third phase being formed by the eighteenth, the twentieth, the twenty-sixth and the thirty-second groups of coils, while the second and the third branches of the said third phase are formed by the fifth, the eleventh, the fourteenth, the nineteenth and by the second, the sixth, the thirty-first groups of coils respectively, the second, the fourth, the seventh, the eighth, the eleventh, the thirteenth, the fifteenth, the eighteenth, the nineteenth, the twenty -two xth, the twenty-fourth, the twenty-sixth, the twenty-ninth, the thirtieth and the thirtieth third group of coils being connected in opposition with respect to the other groups of coils.

 Such an embodiment of the three-phase winding with two layers with switchable poles of a two-speed electric motor makes it possible to obtain a higher average winding coefficient which, in turn, ensures the increase in power per unit of mass. two-speed electric motor. The relative value of the f.é.m. equivalent differential and, consequently, equalizing currents, decreases, which results in an increase in the reliability of the operation and an improvement in the vibroacoustic characteristics of a two-speed electric motor provided with a winding as described above .

 The proposed winding is characterized by a good composition of the magnetizing forces, which makes it possible to simplify the technique of manufacturing two-speed asynchronous electric motors with cage rotors from asynchronous electric motors at one speed with cage rotors, manufactured in series.

Other characteristics and advantages of the invention will be better understood on reading the detailed description which follows of examples of its embodiment illustrated by the appended drawings in which
- Fig. 1 is a block diagram of a three-phase winding with two layers with switchable poles according to the invention for a two-speed electric motor, winding which is housed in 54 notches; and
- Fig. 2 is a connection diagram of the groups of coils in the branches of the phases of the three-phase winding with two layers with switchable poles according to the invention.

Fig. 1 shows a three-phase winding with two layers with switchable poles having six terminals: A6, B6, C6 are the terminals of the first, second and third phases respectively for the higher speed of rotation; A8, B8,
C8 are the terminals of the first, second and third phases respectively for the lower speed of rotation.

The winding is intended to be housed in the 54 stator slots (not shown) of a two-speed electric motor and comprises respectively 54 coils 1,2,3 ... .54
When supplying terminals A8, B8, C8, the winding is coupled as a triple star / YYY / and operates with a number of poles 2pl = 8 (lower speed of rotation)
In order to obtain operation with a number of poles 2p2 = 6 (higher speed of rotation), power must be applied to terminals A6, B6, C6, terminals A8, B8, C8 being de-energized. In this case, the winding is also coupled in triple star / YYY /.

 The coils 1,2,3, ...., 54 are divided into 33 groups of coils 101, 102, 103, .... 133 (Fig. 2), the groups of coils being designated by three-digit numbers in order to make the description clearer. The number of coils in each group of coils, starting from group 101, is determined in accordance with the following numerical series: 3, 2f3tltat2tlf1t2,1,1,3,2,3,1,1,2,1,1,2 , 1,1,3,2,3,1,1,2,1,1,2,2, 1,1. The first, fourth, tenth and twenty-ninth groups of coils -101, 104,110,129- are connected to the first parallel branch of the first phase. The sixteenth, twenty-second, twenty-fifth and thirtieth groups of coils -116, 122, 125, 130- are connected to the second branch of the first phase. The ninth, thirteenth and seventh groups of coils -109,113,117- are connected to the third branch of the first phase. The seventh, twelfth, fifteenth and twenty-first groups of coils -107, 112, 115, 121- are connected to the first branch of the second phase. The third, eighth, twenty-seventh and thirty-third groups of coils -103, 108, 127, 133- are connected to the second branch of the second phase while the twentieth, twenty-fourth and twenty-eighth groups of coils - 120, 124, 128 are connected to the third branch of the second phase. The first parallel branch of the third phase is formed by the eighteenth the twenty-third, the twenty-sixth and the thirty second groups of coils -118, 123, 126, 132, while the other branches of this phase are formed by the fifth, the eleventh, the fourteenth and the nineteenth groups of coils -105, 111, 114, 119- and by the second, the sixth and the thirty-first groups of coils -102,106, 131- respectively. It should be noted that the second, the fourth, the seventh, the eighth, the eleventh, the thirteenth, the fifteenth, the eighteenth, the nineteenth, the twenty-second, the twenty-fourth, the twenty-sixth, the twenty-ninth, thirtieth, thirty-third groups of coils -102, 104, 107, 108, 111, 113, 115, 118, 119, 122, 124, 126, 129, 130, 133 are connected in opposition to the other coil groups.The origins of the coil groups are indicated by dots in Fig. 2.

 In the case of a three-phase winding with two layers with switchable poles of an electric motor with two speeds and 54 notches (Fig.l and 2), the coefficients of winding, with a winding pitch y = 7, are: Kw4 = 0.941, Kw3 = 0.781, Rwo = 0.861, and the ratio of the values of the magnetic inductions in the air gap during engine operation with the number of poles 2pl = 8 and 2p2 = 6 is equal to 1.1, c is close to I.

 The relative value of the f.e.m. equivalent differential does not exceed 2% (a + E = 0.0196).

 The proposed winding is characterized by a high value of the average winding coefficient and by a low relative value of the equivalent differential electromotive force when working with a number of poles 2pl = 8. It provides a report of the magnetic induction values such that it makes it possible to regulate the rotation speed of the motors in stages, the motor torque remaining constant.

Finally, this winding makes it possible to produce, from electric motors at a speed produced in series, electric motors at two speeds characterized by a high power per unit of mass.

 The use of the winding proposed in two-speed motors considerably simplifies the manufacturing technique of these motors and reduces their cost.

Claims (1)

 CLAIM  Three-phase two-layer winding with switchable poles having 6 terminals and comprising fifty-four coils which, with a ratio of the number of poles 2pl: 2p2 = 8: 6, are distributed irregularly into groups of coils forming phases each having three parallel branches during the operation at any number of poles, characterized in that the coils are divided into thirty three groups of coils, the number of coils in each group of coils, starting from the first being determined in accordance with the digital series 3.2, 3.1, 1, 2, 1, 1, 2, 1, 1, 3, 2, 3, 1, 1, 2, 1, 1, 2, 1, 1, 3, 2, 3, 1, 1, 2, 1, 1, 2, 1,1, the first, the fourth, the tenth, the twenty-ninth group of coils being connected to the first branch of the first phase, the sixteenth, the twenty-second, the twenty-fifth and the thirtieth group of coils being connected to the second branch of the first phase the ninth, the thirteenth and the seventeenth group of coils being connected to the a third branch of the first phase, the seventh, the twelfth, the fifteenth and the twenty-first groups of coils being connected to the first branch of the second phase, the third, the eighth, the twenty-seventh and the thirty third groups of coils being connected to the second branch of the second phase, the twentieth, - the twenty-fourth and twenty-eighth groups of coils being connected to the third branch of the second phase, the first branch of the third phase being formed by the eighteenth, twenty-third, twenty-sixth and thirty second groups of coils while the second and third branches of said third phase are formed by the fifth, the eleventh the fourteenth, the nineteenth and by the second, the sixth, the thirty-first groups of coils respectively, the second, the fourth, the seventh, the eighth, the eleventh, the thirteenth, the fifteenth, the eighteenth, the nineteenth, the twenty-second , the twenty-fourth, twenty-sixth, twenty-ninth, thirtieth and thirty-third groups of coils being connected in opposition with respect to the other groups of coils, P1, P2 representing the numbers of pairs of poles corresponding to the lower speeds and superior respectively.