WO2010063869A1 - Solution for damping vibration in an electric machine - Google Patents

Solution for damping vibration in an electric machine Download PDF

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Publication number
WO2010063869A1
WO2010063869A1 PCT/FI2009/000095 FI2009000095W WO2010063869A1 WO 2010063869 A1 WO2010063869 A1 WO 2010063869A1 FI 2009000095 W FI2009000095 W FI 2009000095W WO 2010063869 A1 WO2010063869 A1 WO 2010063869A1
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WO
WIPO (PCT)
Prior art keywords
stator
damper
machine frame
rotor
mounting points
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/FI2009/000095
Other languages
French (fr)
Inventor
Jussi LÄHTEENMÄKI
Gabriela Simbierowicz
Mika Virnes
Janne Rahunen
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Kone Corp
Original Assignee
Kone Corp
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Filing date
Publication date
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Publication of WO2010063869A1 publication Critical patent/WO2010063869A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K5/00—Casings; Enclosures; Supports
    • H02K5/24—Casings; Enclosures; Supports specially adapted for suppression or reduction of noise or vibrations
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/12—Stationary parts of the magnetic circuit
    • H02K1/18—Means for mounting or fastening magnetic stationary parts on to, or to, the stator structures
    • H02K1/185—Means for mounting or fastening magnetic stationary parts on to, or to, the stator structures to outer stators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/46—Fastening of windings on the stator or rotor structure
    • H02K3/50—Fastening of winding heads, equalising connectors, or connections thereto

Definitions

  • the present invention relates to the damping of vibration in an electric machine.
  • a rotating electric machine such as a synchronous and induction motor
  • This magnetic field is produced as a joint effect of stator and rotor magnetizations.
  • the currents flowing in the stator windings produce in the air gap of the machine a rotating magnetic field, whose phase difference relative to the rotor magnetization creates a force effect in the direction of motion of the rotor. This force effect causes the rotor to rotate.
  • the rotor and stator magnetizations together also pro- Jerusalem a force of attraction between stator and rotor.
  • the attractive force is usually multiple times greater than the force causing the rotor to rotate. Since the attractive force appears in the zone where the magnetic field is transferred from rotor to stator and vice versa, the attraction vector rotates in accordance with the magnetic field. Therefore, local variations in the attractive force between stator and rotor may produce vibration in the electric machine.
  • Vibration of an electric machine often produces dis- turbing noise radiating into the environment, and, on the other hand, it may also shorten the service life of mechanical components of the electric machine. Vibration may also be transferred by transmission e.g. via the mounting interface to the environment, such as to the supporting structures surrounding the electric machine .
  • JP 11234956 proposes a radial flux motor in which elastic damping material is fitted between the stator and the machine frame to damp machine vibrations .
  • JP 4096637 proposes an electric machine in which the stator is supported on a stator frame via an elastic spring element.
  • inventive embodiments are also presented in the description part and drawings of the present application.
  • inventive content disclosed in the application can also be defined in other ways than is done in the claims below.
  • inventive content may also consist of several separate inventions, especially if the invention is considered in the light of explicit or implicit sub-tasks or with respect to advantages or sets of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts .
  • the features of different embodiments of the invention can be applied in connection with other embodiments within the scope of the basic inventive concept.
  • the present invention discloses an arrangement for damping vibration in an electric machine.
  • the said electric machine has a stator and a rotor with an air gap fitted between them.
  • the stator is provided with a magnetizing winding for generating a temporally variable magnetic field in the said air gap between stator and rotor.
  • the stator is rigidly attached to the machine frame via at least two different mounting points. Fitted between the stator and machine frame is a damper for damping deflection vibration of the stator.
  • the method of the invention for damping vibrations in an electric machine comprises: fitting a stator and a rotor in the electric machine so that an air gap is formed between the stator and rotor; fitting in the stator a magnetizing winding for producing a temporally varying magnetic field in the said air gap between stator and rotor; securing the stator rigidly to the machine frame via at least two different mounting points; and fitting a damper between the stator and the machine frame to damp deflection vibration of the stator.
  • the damper is fitted in the space between the mounting points, between the stator and the machine frame.
  • the aforesaid air gap between stator and rotor is at least in part of the electric machine unidirectional with the rotational axis of the electric machine, and the stator magnetizing winding is adapted to generate a temporally varying magnetic field in the said air gap substantially unidirectional with the rotational axis, and the stator is rigidly secured to the machine frame via at least two different mounting points, said mounting points being located on the stator back iron in an area such that the area corresponding to it on the opposite side of the stator borders on the aforesaid air gap substantially unidirectional with the ro- tational axis.
  • the damper is adapted to be mechanically connected both to the stator back iron and to the machine frame .
  • the damper is adapted to be mechanically connected to the stator back iron at the point of deflection of the stator between the aforesaid mounting points.
  • Deflection vibration occurs especially between the rigid mounting points joining the stator to the machine frame, and 'point of deflection of the stator' refers to the point at which the amplitude of stator deflection vibration substantially reaches its maximum value.
  • the above- mentioned mounting points can be assumed to constitute zero points of stator deflection.
  • the damping power of the damper can be applied substantially to the point of generation of deflection vibration.
  • the electric machine comprises only one stator and only one rotor.
  • the damper is made of elastic material.
  • the space between the aforesaid mounting points, be- tween the stator and machine frame, is provided with a cooling air channel for cooling the stator and/or damper .
  • the damper is arranged to apply to the stator back iron a damping force, said damping force acting in a substantially perpendicular direction relative to the surface of the stator back iron.
  • deflection vibration can be effectively damped by the damper, be- cause the magnetic attraction causing deflection- vibration likewise acts perpendicularly to the stator back iron.
  • the damper is adapted to be connected between the sta- tor end-winding and the machine frame.
  • the electric machine referred to in the invention may be e.g. an electric motor and/or an electric generator.
  • the magnetizing winding of the stator may be e.g. an alternating current winding, such as a star or delta connected 3 -phase winding, which serves to generate a temporally varying magnetic field in the stator.
  • the winding may be implemented e.g. as a distributed or centralized winding structure.
  • the electric machine of the invention may be e.g. an elevator machine, or an electric machine for operating an escalator or a moving walkway.
  • the aforesaid elevator machine may comprise a drive sheave fitted in conjunction with the rotor.
  • the elevator machine may be installed e.g. in an elevator shaft or in an elevator machine room.
  • the damper is adapted to be connected between the stator end-winding and the machine frame, in which case the damper can serve to reduce deflection vibration at the end wind- ings .
  • the advantages achieved by the invention include at least one of the following.:
  • the stator of the invention is rigidly secured to the machine frame via at . least two different mounting points e.g. by means of bolts and/or by welding.
  • a temporally varying magnetic field is generated in the electric machine, there appears between the stator and rotor a large local force of attraction produced by the magnetic field, and this force also varies temporally.
  • the stator therefore tends to be deflected at the point where the force of attraction is acting.
  • the attractive force acting at the point of deflection varies in accordance with the temporal variation of the magnetic field, and consequently the deflection amplitude also varies.
  • Such deflection vibration occurs especially between the rigid mounting points con- necting the stator to the machine frame.
  • the said mounting points can therefore be regarded as zero points of stator deflection.
  • the deflection vibrations may be resonant vibrations characteristic of the machine, or they may also consist of dying constrained vibration. The nature of the vibration depends, among other things, on the vibration excitation frequency, on the mechanical construction of the machine and on the structure of the stator mounting points.
  • Certain types of mounting point may also constitute a single support mounting in respect of deflection vibration, in which case the supporting force only acts in the direction of the attractive force and the stator can move relative to the mounting point in a direction perpendicular to the di- rection of the attractive force.
  • Deflection vibration can be damped by fitting a damper made of elastic material, such as rubber, between the stator and the machine frame.
  • the vibration can be effectively damped by fitting a damper in the space between the mounting points between stator and machine frame .
  • the stator is rigidly secured to the machine frame by its mounting points.
  • the use of this type of rigid securement pro- vides advantages as compared to prior-art damping solutions.
  • a damper fitted beside rigid securement in the manner described in the invention has no substantial effect on the adjustment of the air gap and/or on variation of the air gap during operation.
  • Rigid se- curement also ensures that the damper is not subjected to excessive forces, which again improves the durability of the damper.
  • the invention is particularly well applicable for use in conjunction with an axial -flux machine, because, without rigid securement, the forces applied to the damper in the direction of the rotational axis would increase to a substantially higher level.
  • the damper as provided by the invention can be secured to the machine frame and/or stator e.g. with a spike, a stud or glue.
  • the machine frame and/or the stator has a machined portion, e.g. a cut-out or groove, forming a place where the damper is fitted.
  • the damper is shape-locked, allowing better control of the compressive force of the damper.
  • the aforesaid shape-locking can also be implemented using some other appropriate structure, and such a structure may also form part of the damper.
  • Fig. 1 represents an electric machine according to the invention
  • Fig. 2 represents a part of a stator according to the invention
  • Fig. 3 represents a damping arrangement according to the invention
  • Fig. 4a represents an electric machine according to the invention
  • Fig. 4b represents force effects in a part of the stator according to the invention
  • Fig. 5 represents an electric machine according to the invention
  • the elevator machine 1 represented by Fig. 1 comprises a discoid stator 2 and a discoid rotor 3 with drive sheave integrated with it. Fitted between the rotor 2 and stator 3 is an air gap 4.
  • the rotor and stator are interconnected by an axle.
  • the axle and the bearings are implemented according to prior art and are not shown here.
  • the motor is an axial-flux motor, so the air gap 4 is substantially unidirectional with the rotational axis of the electric machine.
  • the stator 2 is provided with a three-phase magnetizing winding 5. Rotor magnetization is implemented using permanent magnets mounted on the rotor 3 surface adjacent to the air gap.
  • the permanent magnets on the rotor surface are placed in a mounting matrix, which is made of glass fiber, but which may also be made of e.g. aluminum or some other material having a low magnetic field conductivity.
  • the magnets can also be mounted on the stator by embedding.
  • the magnetic poles of permanent magnets placed next to each other are of mutually opposite polarity.
  • the stator 2 is made of a material having a good magnetic field con- ductivity.
  • the alternating current fed into the magnetizing winding 5 generates a rotating magnetic field in the air gap 4, so the magnetic field in the air gap varies as a function of time.
  • the rotating magnetic field produces a force effect between the rotor 3 and the stator 2.
  • This force effect comprises a component which acts in the direction of the air gap 4 at the point where the magnetic field is transferred from stator to rotor and vice versa.
  • This force component acting in the direction of the air gap 4 generates a local force of attraction varying as a function of time between stator 2 and rotor 3. Because of this force of attraction, the stator 2 tends to undergo deflection.
  • the stator 2 is rigidly secured to the machine frame 6 by bolts at mounting points 7, 7', 7''.
  • the stator tends to undergo deflection especially between the mounting points, and thus the rigid mounting points 7, 7', I' 1 can be regarded as the zero points of deflection.
  • Fig. 4b represents the deflection of a straight- ened-out stator 2 between the rigid mounting points, assuming that the force effect Q acting on the stator is uniformly distributed.
  • the amplitude of the deflection reaches its maximum value v max at the halfway center 1/2 of the distance 1 between mounting points, and the amplitude is roughly consistent with the equation:
  • the force effect Q between the mounting points is generally non-uniformly distributed, and therefore the position and/or magnitude of the deflection amplitude also varies.
  • Fig. 3 visualizes certain possible first- and second-order deflection vibration modes 12, 13. In the second-order vibration mode 13, the vibration frequency is twice as high as in the first-order vibration mode 12. Deflection vibration produces noise which radiates to the surroundings; the vibration is also transmitted via the mounting points 7, V, I 1 ' to the machine frame 6 and further to the mechanical structures connected with the machine.
  • a damper 9 made of rubber is fitted in the space 8 between mounting points 7, T between stator and machine frame.
  • the machine frame 6 is provided with a machined cutout 11, in which the damper is fitted.
  • the function of the cutout is to shape-lock the damper 9 in position; if necessary, the stator 2 can also be provided with a corresponding machined cutout.
  • the thicknesses of the damper 9 is so designed that the damper is pressed against the stator back iron 10, being thus mechanically connected both to the stator back iron 10 and to the machine frame 6.
  • the damper 9 exerts an effect opposing the motion caused by the change in deflection, thereby damping the deflection vibration.
  • the electric machine in Fig. 1, too, comprises a damper 9 fitted between fixing points 7, V between stator and machine frame to damp . deflection vibration of the stator 2.
  • the fixing points 7, 7' are located in the stator back iron in an area 10 corresponding to an area on the opposite side of the stator that is substantially immediately adjacent to the air gap 4 unidirectional with the rotational axis.
  • the dampers can be fitted between the fixing points e.g. in the manner illustrated in Fig. 2. In the space 8 between fixing points 7, 7', I 1 ' there thus also remains be- tween fixing point 7, 7', 7'' and damper 9, 9' an empty space, which functions as a cooling air channel.
  • the stator 2 is cooled by the air flowing in the channel, so the stator winding 5 can be designed for a larger current.
  • the damper 9 can also be fastened both to the stator 2 and to the machine frame 6.
  • the damper to be placed in the space between stator and machine frame can be so designed that, when the stator 2 is bending in the direction away from the machine frame, the damper 9 tends to stretch, applying a pulling force between the stator 2 and the machine frame 6, and when the stator 2 is bending towards the machine frame 6, the damper 9 tends to be compressed, correspondingly applying a pushing force between the stator 2 and the machine frame 6. Securing the damper 9 in this manner is advantageous especially when the stator mounting points 7, 7' form a single support mounting in respect of deflection of the stator 2.
  • Fig. 4a represents a discoid elevator motor 1, in which a damper according to the invention can be fit- ted e.g. in the manner illustrated in the embodiment examples of Figs. 1 - 3.
  • a machine frame 6 Depicted in the figure are a machine frame 6 , and a stator 2 provided with a stator winding 5.
  • the stator 2 is secured to the machine frame via separate mounting points 7, 7' along the whole length of the stator ring.
  • the figure also shows a cutout 11, machined between mounting points 7, 7', where a damper 9 is placed.
  • the elevator motor 1 according to Fig. 5 differs from the one presented in Fig. 4 in that the damper 9 has been fitted to be connected between the stator end winding 14 and the machine frame 6.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Motor Or Generator Frames (AREA)
  • Iron Core Of Rotating Electric Machines (AREA)

Abstract

The invention relates to an arrangement and a method for damping vibration in an electric machine (1). The electric machine has a stator (2) and a rotor (3) with an air gap (4) fitted between them. The stator has a magnetizing winding (5) for generating a temporally variable magnetic field in the said air gap (4) between stator and rotor. The stator is rigidly secured to the machine frame (6) via at least two different mounting points (7, 7', 7''). Fitted in the space (8) between the said mounting points, between the stator and the machine frame, is a damper (9) for damping deflection vibration of the stator (2).

Description

SOLUTION FOR DAMPING VIBRATION IN AN ELECTRIC MACHINE
The present invention relates to the damping of vibration in an electric machine.
The operation of a rotating electric machine, such as a synchronous and induction motor, is based on a magnetic field moving in a stator and rotor. This magnetic field is produced as a joint effect of stator and rotor magnetizations. The currents flowing in the stator windings produce in the air gap of the machine a rotating magnetic field, whose phase difference relative to the rotor magnetization creates a force effect in the direction of motion of the rotor. This force effect causes the rotor to rotate.
The rotor and stator magnetizations together also pro- duce a force of attraction between stator and rotor. The attractive force is usually multiple times greater than the force causing the rotor to rotate. Since the attractive force appears in the zone where the magnetic field is transferred from rotor to stator and vice versa, the attraction vector rotates in accordance with the magnetic field. Therefore, local variations in the attractive force between stator and rotor may produce vibration in the electric machine.
Vibration of an electric machine often produces dis- turbing noise radiating into the environment, and, on the other hand, it may also shorten the service life of mechanical components of the electric machine. Vibration may also be transferred by transmission e.g. via the mounting interface to the environment, such as to the supporting structures surrounding the electric machine .
Specification JP 11234956 proposes a radial flux motor in which elastic damping material is fitted between the stator and the machine frame to damp machine vibrations .
Specification JP 4096637 proposes an electric machine in which the stator is supported on a stator frame via an elastic spring element.
To overcome the above-described problems and to damp the vibrations occurring in an electric machine, a new type of solution for damping vibration in an electric machine is disclosed as an invention. The arrangement of the invention is characterized by what is disclosed in the characterizing part of claim 1. The method of the invention is characterized by what is disclosed in the characterizing part of claim 12. Other embodiments of the invention are character- ized by what is disclosed in the other claims.
Inventive embodiments are also presented in the description part and drawings of the present application. The inventive content disclosed in the application can also be defined in other ways than is done in the claims below. The inventive content may also consist of several separate inventions, especially if the invention is considered in the light of explicit or implicit sub-tasks or with respect to advantages or sets of advantages achieved. In this case, some of the attributes contained in the claims below may be superfluous from the point of view of separate inventive concepts . The features of different embodiments of the invention can be applied in connection with other embodiments within the scope of the basic inventive concept.
The present invention discloses an arrangement for damping vibration in an electric machine. The said electric machine has a stator and a rotor with an air gap fitted between them. The stator is provided with a magnetizing winding for generating a temporally variable magnetic field in the said air gap between stator and rotor. The stator is rigidly attached to the machine frame via at least two different mounting points. Fitted between the stator and machine frame is a damper for damping deflection vibration of the stator.
The method of the invention for damping vibrations in an electric machine comprises: fitting a stator and a rotor in the electric machine so that an air gap is formed between the stator and rotor; fitting in the stator a magnetizing winding for producing a temporally varying magnetic field in the said air gap between stator and rotor; securing the stator rigidly to the machine frame via at least two different mounting points; and fitting a damper between the stator and the machine frame to damp deflection vibration of the stator.
According to one or more embodiments of the invention, the damper is fitted in the space between the mounting points, between the stator and the machine frame.
According to one or more embodiments of the invention, the aforesaid air gap between stator and rotor is at least in part of the electric machine unidirectional with the rotational axis of the electric machine, and the stator magnetizing winding is adapted to generate a temporally varying magnetic field in the said air gap substantially unidirectional with the rotational axis, and the stator is rigidly secured to the machine frame via at least two different mounting points, said mounting points being located on the stator back iron in an area such that the area corresponding to it on the opposite side of the stator borders on the aforesaid air gap substantially unidirectional with the ro- tational axis. According to one or more embodiments of the invention, the damper is adapted to be mechanically connected both to the stator back iron and to the machine frame .
According to one or more embodiments of the invention, the damper is adapted to be mechanically connected to the stator back iron at the point of deflection of the stator between the aforesaid mounting points. Deflection vibration occurs especially between the rigid mounting points joining the stator to the machine frame, and 'point of deflection of the stator' refers to the point at which the amplitude of stator deflection vibration substantially reaches its maximum value. In respect of deflection vibration, the above- mentioned mounting points can be assumed to constitute zero points of stator deflection. Thus, the damping power of the damper can be applied substantially to the point of generation of deflection vibration.
According to one or more embodiments of the invention, the electric machine comprises only one stator and only one rotor.
According to one or more embodiments of the invention, the damper is made of elastic material.
According to one or more embodiments of the invention, the space between the aforesaid mounting points, be- tween the stator and machine frame, is provided with a cooling air channel for cooling the stator and/or damper .
According to one or more embodiments of the invention, the machine frame and/or the stator back iron com- prise/comprises a machined portion forming a place where the damper is fitted.
According to one or more embodiments of the invention, the damper is arranged to apply to the stator back iron a damping force, said damping force acting in a substantially perpendicular direction relative to the surface of the stator back iron. Thus, deflection vibration can be effectively damped by the damper, be- cause the magnetic attraction causing deflection- vibration likewise acts perpendicularly to the stator back iron.
According to one or more embodiments of the invention, the damper is adapted to be connected between the sta- tor end-winding and the machine frame.
The electric machine referred to in the invention may be e.g. an electric motor and/or an electric generator. The magnetizing winding of the stator may be e.g. an alternating current winding, such as a star or delta connected 3 -phase winding, which serves to generate a temporally varying magnetic field in the stator. The winding may be implemented e.g. as a distributed or centralized winding structure.
The electric machine of the invention may be e.g. an elevator machine, or an electric machine for operating an escalator or a moving walkway. The aforesaid elevator machine may comprise a drive sheave fitted in conjunction with the rotor. The elevator machine may be installed e.g. in an elevator shaft or in an elevator machine room.
In an embodiment of the invention, the damper is adapted to be connected between the stator end-winding and the machine frame, in which case the damper can serve to reduce deflection vibration at the end wind- ings .
The advantages achieved by the invention include at least one of the following.: The stator of the invention is rigidly secured to the machine frame via at. least two different mounting points e.g. by means of bolts and/or by welding. When a temporally varying magnetic field is generated in the electric machine, there appears between the stator and rotor a large local force of attraction produced by the magnetic field, and this force also varies temporally. The stator therefore tends to be deflected at the point where the force of attraction is acting. The attractive force acting at the point of deflection varies in accordance with the temporal variation of the magnetic field, and consequently the deflection amplitude also varies. Such deflection vibration occurs especially between the rigid mounting points con- necting the stator to the machine frame. In respect of deflection vibration, the said mounting points can therefore be regarded as zero points of stator deflection. The deflection vibrations may be resonant vibrations characteristic of the machine, or they may also consist of dying constrained vibration. The nature of the vibration depends, among other things, on the vibration excitation frequency, on the mechanical construction of the machine and on the structure of the stator mounting points. Certain types of mounting point may also constitute a single support mounting in respect of deflection vibration, in which case the supporting force only acts in the direction of the attractive force and the stator can move relative to the mounting point in a direction perpendicular to the di- rection of the attractive force. Deflection vibration can be damped by fitting a damper made of elastic material, such as rubber, between the stator and the machine frame.
Since deflection vibration of the stator occurs be- tween the mounting points, the vibration can be effectively damped by fitting a damper in the space between the mounting points between stator and machine frame . In the solution of the invention, the stator is rigidly secured to the machine frame by its mounting points. The use of this type of rigid securement pro- vides advantages as compared to prior-art damping solutions. A damper fitted beside rigid securement in the manner described in the invention has no substantial effect on the adjustment of the air gap and/or on variation of the air gap during operation. Rigid se- curement also ensures that the damper is not subjected to excessive forces, which again improves the durability of the damper.
The invention is particularly well applicable for use in conjunction with an axial -flux machine, because, without rigid securement, the forces applied to the damper in the direction of the rotational axis would increase to a substantially higher level.
The damper as provided by the invention can be secured to the machine frame and/or stator e.g. with a spike, a stud or glue. In a preferred embodiment of the invention, the machine frame and/or the stator has a machined portion, e.g. a cut-out or groove, forming a place where the damper is fitted. In this manner, the damper is shape-locked, allowing better control of the compressive force of the damper. If necessary, the aforesaid shape-locking can also be implemented using some other appropriate structure, and such a structure may also form part of the damper.
If necessary, it is also possible to provide in the space between the mounting points between stator and machine frame a cooling air duct for supplying cooling air to cool down the stator and/or damper. LIST OF FIGURES
Fig. 1 represents an electric machine according to the invention
Fig. 2 represents a part of a stator according to the invention
Fig. 3 represents a damping arrangement according to the invention
Fig. 4a represents an electric machine according to the invention Fig. 4b represents force effects in a part of the stator according to the invention
Fig. 5 represents an electric machine according to the invention
DETAILED DESCRIPTION OF THE INVENTION
The elevator machine 1 represented by Fig. 1 comprises a discoid stator 2 and a discoid rotor 3 with drive sheave integrated with it. Fitted between the rotor 2 and stator 3 is an air gap 4. The rotor and stator are interconnected by an axle. The axle and the bearings are implemented according to prior art and are not shown here. The motor is an axial-flux motor, so the air gap 4 is substantially unidirectional with the rotational axis of the electric machine. The stator 2 is provided with a three-phase magnetizing winding 5. Rotor magnetization is implemented using permanent magnets mounted on the rotor 3 surface adjacent to the air gap. The permanent magnets on the rotor surface are placed in a mounting matrix, which is made of glass fiber, but which may also be made of e.g. aluminum or some other material having a low magnetic field conductivity. On the other hand, the magnets can also be mounted on the stator by embedding. The magnetic poles of permanent magnets placed next to each other are of mutually opposite polarity. The stator 2 is made of a material having a good magnetic field con- ductivity.
The alternating current fed into the magnetizing winding 5 generates a rotating magnetic field in the air gap 4, so the magnetic field in the air gap varies as a function of time. When the rotor is rotating, the magnetic field produced in the air gap by the rotor magnetization varies, too. The rotating magnetic field produces a force effect between the rotor 3 and the stator 2. This force effect comprises a component which acts in the direction of the air gap 4 at the point where the magnetic field is transferred from stator to rotor and vice versa. This force component acting in the direction of the air gap 4 generates a local force of attraction varying as a function of time between stator 2 and rotor 3. Because of this force of attraction, the stator 2 tends to undergo deflection.
The stator 2 is rigidly secured to the machine frame 6 by bolts at mounting points 7, 7', 7''. The stator tends to undergo deflection especially between the mounting points, and thus the rigid mounting points 7, 7', I'1 can be regarded as the zero points of deflection. Fig. 4b represents the deflection of a straight- ened-out stator 2 between the rigid mounting points, assuming that the force effect Q acting on the stator is uniformly distributed. The amplitude of the deflection reaches its maximum value vmax at the halfway center 1/2 of the distance 1 between mounting points, and the amplitude is roughly consistent with the equation:
-o*ι4
384*£*i\ where the symbol E represents the module of elasticity of the stator and the symbol Iy represents the square moment of the stator.
In practice, the force effect Q between the mounting points is generally non-uniformly distributed, and therefore the position and/or magnitude of the deflection amplitude also varies.
Since the local attractive force exerted on the stator 2 varies temporally as a function of the speed of ro- tation of the magnetic field, the amplitude of stator deflection also varies in accordance with the speed of rotation of the magnetic field. This cyclic variation of the deflection results in deflection vibration of the stator. Fig. 3 visualizes certain possible first- and second-order deflection vibration modes 12, 13. In the second-order vibration mode 13, the vibration frequency is twice as high as in the first-order vibration mode 12. Deflection vibration produces noise which radiates to the surroundings; the vibration is also transmitted via the mounting points 7, V, I1' to the machine frame 6 and further to the mechanical structures connected with the machine. To damp the vibration, a damper 9 made of rubber is fitted in the space 8 between mounting points 7, T between stator and machine frame. The machine frame 6 is provided with a machined cutout 11, in which the damper is fitted. The function of the cutout is to shape-lock the damper 9 in position; if necessary, the stator 2 can also be provided with a corresponding machined cutout. The thicknesses of the damper 9 is so designed that the damper is pressed against the stator back iron 10, being thus mechanically connected both to the stator back iron 10 and to the machine frame 6. When the attractive force produced by the rotating magnetic field begins to decrease and the deflected stator 2 conse- quently begins to straighten out, the damper 9 exerts an effect opposing the motion caused by the change in deflection, thereby damping the deflection vibration.
The electric machine in Fig. 1, too, comprises a damper 9 fitted between fixing points 7, V between stator and machine frame to damp .deflection vibration of the stator 2. The fixing points 7, 7' are located in the stator back iron in an area 10 corresponding to an area on the opposite side of the stator that is substantially immediately adjacent to the air gap 4 unidirectional with the rotational axis. The dampers can be fitted between the fixing points e.g. in the manner illustrated in Fig. 2. In the space 8 between fixing points 7, 7', I1' there thus also remains be- tween fixing point 7, 7', 7'' and damper 9, 9' an empty space, which functions as a cooling air channel. The stator 2 is cooled by the air flowing in the channel, so the stator winding 5 can be designed for a larger current. The damper 9 can also be fastened both to the stator 2 and to the machine frame 6. In this case, the damper to be placed in the space between stator and machine frame can be so designed that, when the stator 2 is bending in the direction away from the machine frame, the damper 9 tends to stretch, applying a pulling force between the stator 2 and the machine frame 6, and when the stator 2 is bending towards the machine frame 6, the damper 9 tends to be compressed, correspondingly applying a pushing force between the stator 2 and the machine frame 6. Securing the damper 9 in this manner is advantageous especially when the stator mounting points 7, 7' form a single support mounting in respect of deflection of the stator 2.
Fig. 4a represents a discoid elevator motor 1, in which a damper according to the invention can be fit- ted e.g. in the manner illustrated in the embodiment examples of Figs. 1 - 3. Depicted in the figure are a machine frame 6 , and a stator 2 provided with a stator winding 5. The stator 2 is secured to the machine frame via separate mounting points 7, 7' along the whole length of the stator ring. The figure also shows a cutout 11, machined between mounting points 7, 7', where a damper 9 is placed.
The elevator motor 1 according to Fig. 5 differs from the one presented in Fig. 4 in that the damper 9 has been fitted to be connected between the stator end winding 14 and the machine frame 6.
It is obvious to a person skilled in the art that the invention is not limited to the above-explained em- bodiments describing the invention by way of example, but that many variations and different embodiments of the invention are feasible within the scope of the inventive concept defined in the attached claims.

Claims

1. Arrangement for damping vibration in an electric machine (1) , said electric machine having a stator (2) and a rotor (3) with an air gap (4) fitted between them, and said stator having a magnetizing winding (5) for generating a temporally variable magnetic field in the said air gap (4) between stator and rotor, and said stator being rigidly secured to a machine frame (6) via at least two different mounting points (7, 7', 7"), characterized in that a damper is fitted between the stator (2) and the machine frame (6) , for damping deflection vibration of the stator (2) .
2. Arrangement according to claim 1, characterized in that the damper (9) is fitted in the space (8) between the mounting points (7, 7', I1'), between the stator (2) and the machine frame (6) .
3. Arrangement according to claim 1 or 2 , character- ized in that the aforesaid air gap (4) between stator and rotor is at least in part of the electric machine unidirectional with the rotational axis of the electric machine, and that the stator magnetizing winding (5) is adapted to generate a temporally varying magnetic field in the said air gap substantially unidirectional with the rotational axis, and that the stator (2) is rigidly secured to the machine frame (6) via at least two different mounting points (7, 7', I'1), said mounting points being located on the stator back iron in an area (10) such that the area corresponding to it on the opposite side of the stator is adjacent to the aforesaid air gap substantially unidirectional with the rotational axis.
4. Arrangement according to any one of the preceding claims, characterized in that the damper (9) is adapted to be mechanically connected both to the sta- tor back iron (10) and to the machine frame (6) .
5. Arrangement according to any one of the preceding claims, characterized in that the damper (9) is adapted to be mechanically connected to the stator back iron (10) at the point of stator deflection between the aforesaid mounting points (7, 7', 1' ') .
6. Arrangement according to any one of the preceding claims, characterized in that the electric machine comprises only one stator (2) and only one rotor (3) .
7. Apparatus Arrangement according to any one of the preceding claims, characterized in that the damper (9) is made of elastic material.
8. Arrangement according to any one of the preceding claims, characterized in that the space (8) between the aforesaid mounting points, between the stator and the machine frame, is provided with a cooling air channel for cooling the stator (2) and/or damper (9) .
9. Arrangement according to any one of the preceding claims, characterized in that the machine frame (6) and/or the stator back iron (10) comprise/comprises a machined portion forming a place (11) where the damper (9) is fitted.
10. Arrangement according to any one of the preceding claims, characterized in that the damper is arranged to apply a damping force to the stator back iron, said damping force acting in a substantially perpendicular direction relative to the surface of the stator back iron.
11. Arrangement according to any one of the preceding claims, characterized in that the damper (9) is adapted to be connected between the stator end-winding (14) and the machine frame (6)..
12. Method for damping vibration in an electric machine (1) , said method comprising: - fitting a stator (2) and a rotor (3) in the electric machine so that an air gap (4) is formed between the stator and rotor
- fitting in the stator a magnetizing winding (2) for producing a temporally varying magnetic field in the said air gap (4) between the stator and rotor
- securing the stator (2) rigidly to the machine frame (6) via at least two different mounting points (7, 7', I'1) characterized in that
- a damper (9) is fitted between the stator (2) and the machine frame (6) to damp deflection vibration of the stator.
13. Method according to claim 12, characterized in that
- the damper (9) is adapted to be mechanically connected both to the stator back iron (10) and to the machine frame (6) .
14. Method according to claim 12 or 13, characterized in that
- the damper (9) is adapted to be mechanically connected to the stator back iron (10) at the point of stator deflection between the aforesaid mounting points (7, 7' , 7' ' ) .
15. Method according to any one of claims 12 - 14, characterized in that
- a damping force is applied to the stator back iron (10) by means of the damper (9) in a sub- stantially perpendicular direction relative to the surface of the stator back iron.
PCT/FI2009/000095 2008-12-01 2009-11-10 Solution for damping vibration in an electric machine Ceased WO2010063869A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20080644 2008-12-01
FI20080644A FI122752B (en) 2008-12-01 2008-12-01 Solution for vibration damping in electrical machinery

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WO2010063869A1 true WO2010063869A1 (en) 2010-06-10

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WO (1) WO2010063869A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2873637A1 (en) 2013-11-13 2015-05-20 Kone Corporation A hoisting machine, an elevator assembly, and improvement in vibration damping of a hoisting machine and in an elevator assembly

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1416371A (en) * 1972-01-24 1975-12-03 Gen Electric Dynamoelectric machine
US6091177A (en) * 1999-03-22 2000-07-18 Siemens Westinghouse Power Corporation Spring mounting for an electric generator

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1416371A (en) * 1972-01-24 1975-12-03 Gen Electric Dynamoelectric machine
US6091177A (en) * 1999-03-22 2000-07-18 Siemens Westinghouse Power Corporation Spring mounting for an electric generator

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2873637A1 (en) 2013-11-13 2015-05-20 Kone Corporation A hoisting machine, an elevator assembly, and improvement in vibration damping of a hoisting machine and in an elevator assembly
CN104627796A (en) * 2013-11-13 2015-05-20 通力股份公司 Hoisting machine, an elevator assembly, and improvement in vibration damping of a hoisting machine and in an elevator assembly
US10071883B2 (en) 2013-11-13 2018-09-11 Kone Corporation Hoisting machine with vibrating damping and an elevator assembly

Also Published As

Publication number Publication date
FI20080644A0 (en) 2008-12-01
FI122752B (en) 2012-06-29
FI20080644L (en) 2010-06-02

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