DE8414158U1 - Noise-reducing casing for a fin-cooled electrical machine - Google Patents

Description

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Siemens Aktiengesellschaft Our sign Berlin and Munich VPA MP 3 1 6 1 OE

S Noise-reducing casing for a fin-cooled electrical machine

The invention relates to a sound-reducing casing for a fin-cooled electrical machine with noticeable magnetic noise components of any tone frequency, in particular converter-fed asynchronous motors with constant or variable tone frequencies.

In such machines, in addition to fan noise and bearing noise, there are also magnetically generated sounds, particularly those excited by field harmonics, which often form the predominant noise component due to the reduced fan and bearing noise in modern machines with an increasing number of poles and in pole-changing machines. In this context, converter-fed machines with modified

Asynchronous motors operated at high speeds are particularly problematic, since the distorted voltages and currents of the motor, which deviate from the sinusoidal shape, result in additional fundamental and harmonic fields in the air gap, which rotate with a correspondingly higher harmonic rotation frequency. If the speed of the motors changes, the frequencies of the tones in question also change, inevitably passing through the natural frequencies of the various machine parts, such as the stator core, machine housing, its cooling fins, rotor shaft, etc.

Until now, a hood has been provided as a sound-reducing enclosure that encloses the entire machine. This hood is attached around the machine at the installation site and must be at least partially removed when accessing parts of the machine.

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- 2 - VPA WP 3 161 EN

The invention is based on the object of reducing the magnetically induced noise to a lower overall noise level by means of a casing which, when mounted on the machine, forms a transport unit with it and which allows operational interventions in or on the machine without partial or complete removal from the machine.

The solution to the problem is achieved by the characterizing features of patent claim 1.

^ Depending on the desired noise reduction and the type of fastening, the casing can be made of sheet metal or solid plastic, whereby the sheet metal is uncoated or provided with an internal structure-borne sound-damping layer and/or an airborne sound-absorbing lining, and the plastic is, for example, glass fiber reinforced. The casing can be made entirely or partially of sheet metal or plastic and have an open U-shaped or closed ring-shaped contour, whereby the casing can also be made of the same material and closed on the periphery in one piece.

( ' Further details of the invention are explained below using an embodiment.

Fig. 1 a half longitudinal section or side view of a machine with a B-side externally driven fan unit with a housing of angular contour, Fig. 2 a cross section along the line II-II of the object according to Fig. 1,

Fig. 3 and 4 Details of the fastening of the jacket to the housing or the baseboards,

Fig. 5 a variant of the invention in perspective view. 35

A closed, surface-cooled asynchronous motor with a segmented externally ribbed housing 1 with round

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- 3 - VPA WP 3 161 EN

The inner contour and the octagonal outer contour due to the cooling fins 1A arranged axially in segments have fastening surfaces 1B between the fin segments for screw-on baseboards 2 and transport lugs 3 as well as for a sound-reducing jacket 4, which is screwed to the housing via body-sound-damping spacers 5 as shown in Fig. 3, so that the jacket 4 has a distance from the cooling fins 1A at the other points, which improves the cooling air flow and largely prevents the transmission of structure-borne noise from the cooling fins and the housing to the jacket. The jacket 4, which is open at the bottom, U-shaped in cross-section ( ) and otherwise in one piece, can be made of sheet metal without or with a sound-deadening layer and/or airborne sound-absorbing lining or only of, for example, glass fiber reinforced plastic. The side walls of the jacket 4 are also screwed to the baseboards 2 as shown in Fig. 4 to reduce noise.

The side walls of the casing 4 have recesses 4A in the area of the baseboards 2, which allow free access to the fastening means of the baseboards and to the floor area (not shown). In addition, the casing 4 has recesses 4B for a housing projection 1C for ( ) fastening the terminal box 6 and at least one recess (not shown) for the transport eyelet 3.

The casing extends beyond the B-side bearing plate 1E and carries an externally driven fan unit at the end. 8, whereby the casing between the bearing plate 1E and the mounting plate 8A of the fan unit is completed on the underside by a noise-reducing lower part 4C to form a fan cover.

In a representation according to Fig. 5, the lower part of the machine can be sound-absorbingly protected by a sound-reducing cover (omitted in the figure for the sake of simplicity) that is firmly attached to the casing part made of structure-borne sound-damped sheet metal and provided with recesses for the baseboards w.

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- 4 - VPA WP 3 161 EN

be covered by a glass-fiber-reinforced plastic casing part 9, so that a circumferentially closed, divided casing is produced.

The fastening of the casing 4 to the housing 1 can be carried out according to Fig. 1 by means of tubular structure-borne sound insulators 5 penetrated by fastening screws together with spacers 5A in order to achieve a sufficient distance between the casing and the machine housing ¹ , whereas when fastening the casing 4 to the baseboards 2 according to Fig. 4 with shorter structure-borne sound insulators 51, spacers can be dispensed with.

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Claims (12)

1. Noise-reducing casing for a fin-cooled electrical machine with noticeable magnetic noise components of any audio frequency, characterized in that a noise-reducing casing (4) is provided on the machine housing (1) which is detachably attached and leaves the mechanical and electrical coupling points (e.g. baseboards, terminal box, lifting eyes) and the free shaft end (α-side) freely accessible and forms a transport unit with the machine. i ' 2. Covering according to claim 1, characterized in that the casing (4) consists at least partially of sheet metal. 15 3. Covering according to claim 2, characterized in that the casing is at least partially provided with an internal structure-borne sound-damping layer and/or an airborne sound-absorbing lining. 4. Covering according to claim 1, characterized in that i"&igr; indicates that the casing (4) is at least partly made of glass fibre reinforced plastic. 2S 5. Covering according to one of the preceding claims, characterized in that the casing (4) extending from the A-side bearing plate (1D) at least over the length of the housing is adapted in its contour to the contour of the ribbed machine housing (1, 1A) and is held at a distance from it. 6. Covering according to at least one of the preceding claims, characterized in that the jacket is in one piece. ·■ ·■ &igr;» >·■■ *· · r ·· »Si 111* · ·■ ·· I 111) 1 &igr; t * »«*·· I * jii > * · ■ ■ 1 «1 1 1 J * » f« · - 6 - VPA WP 3 161 EN 7. Covering according to at least one of claims 1 to 5, characterized in that the casing is composed of several casing parts attached to the machine circumference. 8. Cover according to claim 6 or 7, characterized in that the casing (4) has a U-shaped contour at least in the area of the machine housing (1). y! 10 9. Covering according to claim 8, characterized in that the casing (4) extends in the axial direction B-side in an annular contour over the machine housing (1) (4) and serves as a support and fan cover for a fan that is detachably attached to the front. f 15 aggregate (8) is formed. h1
10. Covering according to claim 6 or 7, characterized in that the jacket in * Circumferential direction is closed ring-shaped. 20 11. Covering according to claim 7 and 10, characterized in that the two-part jacket (4) consists of a U-shaped contoured structure-borne sound ■ dampened sheet metal casing part and a glass fibre reinforced plastic casing part (9) fixed in the foot area on the skirts (2). 12. Covering according to one or more of the preceding claims, characterized in that the casing (4, 4C) is secured by fastening screws ■ penetrated structure-borne sound insulators (5, 5') are kept at a distance from the machine housing (1) or the baseboards (2) ■ are screwed to them.