GB1581694A - Rotors for induction motors - Google Patents

Description

(54) ROTORS FOR INDUCTION MOTORS (71) We, SIEMENS AKTIENGESELLSCHAFT, a German company of Berlin and Munich, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to rotors for induction motors. Rotor windings of induction motors, particularly motors of relatively low power, are usually manufactured as so-called cast squirrel-cage windings. A rotor which, in contrast thereto, has a wound rotor winding has been proposed in German Patent Application No. P 25 30 294.7.

According to the present invention, there is provided a wound rotor for an induction motor, comprising a full-pitch winding which has a coil span equal to an odd integral multiple n of the pole pitch, of the winding the particular chosen value of n being that which gives a coil span nearest to 1800 mechanical.

Thus, n is chosen as an optimum value to give a coil span which is as close to 1800 mechanical as possible.

In a particular embodiment of the invention, the rotor comprises three-phase windings, each of which has a coil span of less than 1800 mechanical. A particularly advantageous application of the invention is obtained in the case of a two-motor drive, more particularly for an automatic washing machine drive having an induction motor for the wash operation and a series commutator motor for the spin operation. in which drive the stator winding and the rotor winding of the induction motor and of the commutator motor are disposed in a common single stator assembly and a common rotor assembly, respectively.

The cost of manufacture of a rotor in accordance with the invention can be made relatively low by employing, for the manufacture and/ or introduction of the winding into rotor slots, a machine winding device of the type known per se for the production of commutator-rotor windings of low-pole, more particularly two-pole, construction.

One winding device of this type is known to us as a "Flyer".

For a better understanding of the invention and to show how the same may be carried into effect, reference will be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 is a winding diagram of conventional six-pole induction motor rotor threephase windings having a coil span w = where 7p is the pole pitch; Figure 2 is a winding diagram corresponding to Figure 1 but with the coil span increased, in accordance with the invention, to w = 3 sp; Figure 3 is a winding diagram of a conventional eight-pole induction motor rotor three-phase winding having a coil span of w = Tp; and Figure 4 is a winding diagram corresponding to Figure 3 but with the coil span increased, in accordance with the invention, to w = 3 to.

The conventional six-pole induction motor rotor three-phase windings illustrated in Figure 1 are accommodated in 18 slots of a rotor, with a coil span of w = Tp. The first phase winding is introduced into the slots 1, 4, 7, 10, 13, 16 to give the flux direction into the slots 1, 4, 7, 10, 13, 16 to give the flux direction in the drawing by arrows. In Figure 2, the coil span w is increased to 3 to, SO that a so-called diametral full-pitch winding is obtained, which has the same number of poles as the winding according to Figure 1, but is substantially easier to manufacture.

Since, with a winding construction according to Figure 2, the slots associated with two opposite sides of the coil lie substantially opposite one another in the rotor, the induction motor winding can be machine-wound into the slots of the commutator in the man ner of a low-pole (more particularly twopole) wound commutator winding, the winding being wound in a manner knownperse by means of a so-called "Flyer" machine.

Figures 3 and 4 again show respectively, for the sake of comparison, a conventional induction motor rotor winding having a coil span w = Tp, and a rotor winding having a coil span of w = 3rip, extended into a fullpitch winding in accordance with the invention, in the case of an eight-pole rotor having 24 slots. For the sake of clarity, the respective windings extended in accordance with the invention are shown in Figures 2 and 4 only for one phase winding, and are correspondingly applicable to the remaining phase windings.

The common feature of the Figure 2 and Figure 4 embodiments is that the coil span is an odd integral multiple of the pole pitch, the integral multiple being so chosen as an optimum value as to give a coil span of as near 1800 mechanical as possible.

The additional copper which may be required for a rotor winding construction as illustrated in Figures 2 and 4 for the production of the end connections and for ensuring a particular minimum rotor resistance is, we have found, only of minor importance as compared with the advantage that the winding can be produced and introduced into the rotor slots in a simple and reliable manner by machine.

WHAT WE CLAIM IS: 1. A wound rotor for an induction motor, comprising a full-pitch winding which has a coil span equal to an odd integral multiple n of the pole pitch, of the winding, the particular chosen value of n being that which gives a coil span nearest to 1800 mechanical.

2. A rotor according to claim 1, wherein said winding is disposed in slots in the rotor.

3. A rotor according to claim 1 or 2, comprising three-phase windings, each of which has a coil span of less than 1800 mechanical.

4. A wound rotor for an induction motor. the rotor being substantially as hereinbefore described with reference to Figure 2 or 4 of the accompanying drawings.

5. An induction motor provided with a rotor according to claim 1, 2, 3 or 4.

6. An induction motor according to claim 5 in combination with a series wound commutator motor, the two motors sharing a common stator assembly and a common rotor assembly to provide a single drive.

7. A washing machine provided with a motor combination according to claim 6. the induction motor being for use in a washing operation and the commutator motor being for use in a spinning operation.

8. A method of manufacturing a rotor according to claim 1. 2. 3 or 4. including the step of producing said winding or windings by means of a machine winding apparatus of the type suitable for use in winding a wound commutator rotor having a low number of poles.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. ner of a low-pole (more particularly twopole) wound commutator winding, the winding being wound in a manner knownperse by means of a so-called "Flyer" machine. Figures 3 and 4 again show respectively, for the sake of comparison, a conventional induction motor rotor winding having a coil span w = Tp, and a rotor winding having a coil span of w = 3rip, extended into a fullpitch winding in accordance with the invention, in the case of an eight-pole rotor having 24 slots. For the sake of clarity, the respective windings extended in accordance with the invention are shown in Figures 2 and 4 only for one phase winding, and are correspondingly applicable to the remaining phase windings. The common feature of the Figure 2 and Figure 4 embodiments is that the coil span is an odd integral multiple of the pole pitch, the integral multiple being so chosen as an optimum value as to give a coil span of as near 1800 mechanical as possible. The additional copper which may be required for a rotor winding construction as illustrated in Figures 2 and 4 for the production of the end connections and for ensuring a particular minimum rotor resistance is, we have found, only of minor importance as compared with the advantage that the winding can be produced and introduced into the rotor slots in a simple and reliable manner by machine. WHAT WE CLAIM IS:

1. A wound rotor for an induction motor, comprising a full-pitch winding which has a coil span equal to an odd integral multiple n of the pole pitch, of the winding, the particular chosen value of n being that which gives a coil span nearest to 1800 mechanical.

2. A rotor according to claim 1, wherein said winding is disposed in slots in the rotor.

3. A rotor according to claim 1 or 2, comprising three-phase windings, each of which has a coil span of less than 1800 mechanical.

4. A wound rotor for an induction motor. the rotor being substantially as hereinbefore described with reference to Figure 2 or 4 of the accompanying drawings.

5. An induction motor provided with a rotor according to claim 1, 2, 3 or 4.

6. An induction motor according to claim 5 in combination with a series wound commutator motor, the two motors sharing a common stator assembly and a common rotor assembly to provide a single drive.

7. A washing machine provided with a motor combination according to claim 6. the induction motor being for use in a washing operation and the commutator motor being for use in a spinning operation.

8. A method of manufacturing a rotor according to claim 1. 2. 3 or 4. including the step of producing said winding or windings by means of a machine winding apparatus of the type suitable for use in winding a wound commutator rotor having a low number of poles.