Electric motor comprising an acoustic attenuation device

1. An electric motor, comprising:

a frame defining an inner volume wherein is accommodated a rotor, a stator and a fan, the frame comprising:

a first aperture placing the inner volume of the frame in fluidic communication with the outside of the frame, and

a second aperture placing the inner volume of the frame in fluidic communication with the outside of the frame according to a radial axis perpendicular to an axis of rotation of the rotor,

the fan being positioned in the vicinity of the second aperture and being configured for generating a gas fluid flow, wherein

at least one acoustic attenuation device is accommodated in the second aperture so as to partly close the second aperture,

the second aperture comprises at least one first passage and one second passage for letting through the gas fluid, the at least one acoustic attenuation device accommodated in and closing the first passage,

the first passage and the second passage are defined at least partially by the frame and are adapted for the passage of the flow of the gas fluid between the inner volume of the frame and the outside of the frame,

the first passage extends along a first radial axis, the second passage extends along a second radial axis different from the first radial axis, said first and second radial axis extend in a plane perpendicular to the rotation axis of the rotor, and the first passage and the second passage are circumferentially arranged around the rotation axis of the rotor, and

the motor comprises a casing mounted to the frame, the casing comprising at least one soundless area arranged facing the first passage and not allowing the passing of the gas fluid, and at least one area arranged facing the second passage and allowing the gas fluid and the soundless area of the casing bearing the at least one acoustic attenuation device.

2. The electric motor according to claim 1 , wherein the fan is a centrifugal fan.

3. The electric motor according to claim 1 , wherein the acoustic attenuation device has a multilayer structure comprising a soundless bottom layer, at least one cavity layer applied on the bottom layer, and a sound passage layer applied on the cavity layer.

4. The electric motor according to claim 3 , wherein the cavity layer is formed with at least one cylinder with a hexagonal base extending over a predefined distance between the bottom layer and the sound passage layer.

5. The electric motor according to claim 3 , wherein the multilayer structure comprises several superimposed cavity layers.

6. The electric motor according to claim 3 , wherein the first sound passage layer is formed by a metal sheet including micro-holes.

7. The electric motor according to claim 3 , wherein the bottom layer is formed by a closed metal sheet.

8. The electric motor according to claim 3 , wherein the acoustic attenuation device is secured to the casing, the casing being mounted on the frame so that the sound passage layer—is oriented towards the fan.

9. The electric motor according to claim 8 , wherein the casing is formed in at least two parts configured for partly covering the second aperture.

10. The electric motor according to claim 1 , further comprising a plurality of additional first passages and a plurality of additional second passages, the first passage and the additional first passages providing a first passage group and the second passage and the additional second passages providing a second passage group, and wherein the passages of the first passage group and the passages of the second passage group are alternatively arranged around the rotation axis of the rotor.

11. The electric motor according to claim 1 , wherein the first passage and the second passage are circumferentially spaced from one another about the rotation axis of the rotor.

12. The electric motor according to claim 1 , wherein the first passage and the second passage are arranged circumferentially adjacent one another.

13. An electric motor, comprising:

a frame defining an inner space in which a rotor, a stator and a fan are housed, the frame comprising:

a first aperture placing the inner volume of the frame in fluid communication with an outside of the frame, and

a second aperture placing the inner volume of the frame in fluid communication with the outside of the frame along a radial axis perpendicular to a rotation axis of the rotor,

the fan being arranged in the vicinity of the second aperture and being configured for generating a flow of a gaseous fluid,

the second opening comprising at least one first passage and at least one second passage for the passage of the gaseous fluid, said at least one first passage and at least one second passage being through slots defined in the frame and arranged around the rotation axis of the rotor, and

the electric motor further comprising:

at least one acoustic attenuation device accommodated in the at least one first passage to close the first passage, at least one soundless area placed facing the first passage and not allowing the passing of the gas fluid flow, and at least one area for letting through air placed facing the second passage and allowing the passing of the gas fluid flow, the soundless area of the casing bearing the at least one acoustic attenuation device.

14. The electric motor according to claim 13 , wherein the first passage and the second passage are defined at least partially by the frame.

15. The electric motor according to claim 13 , further comprising a plurality of additional first passages and a plurality of additional second passages, the first passage and the additional first passages providing a first passage group and the second passage and the additional second passages providing a second passage group, and wherein the passages of the first passage group and the passages of the second passage group are alternatively arranged around the rotation axis of the rotor.

16. The electric motor according to claim 13 , wherein the first passage and the second passage are adapted for the passage of the flow of the gas fluid between the inner space of the frame and the outside of the frame.

17. The electric motor according to claim 13 , wherein the first passage and the second passage are circumferentially arranged about the rotation axis of the rotor.

18. The electric motor according to claim 13 , wherein the first passage and the second passage are circumferentially spaced from one another about the rotation axis of the rotor.

19. The electric motor according to claim 13 , wherein the first passage extends along a first radial axis, and the second passage extends along a second radial axis different from the first radial axis, and wherein said first and second radial axes extend in a plane perpendicular to the rotation axis of the rotor.

20. The electric motor according to claim 13 , wherein the acoustic attenuation device has a multilayer structure comprising a bottom layer soundless, at least one cavity layer applied on the bottom layer and a sound passage layer applied on the cavity layer.