EP3084954A2

EP3084954A2 - Electric motor

Info

Publication number: EP3084954A2
Application number: EP14830717.6A
Authority: EP
Inventors: Carlos Josè CEVA
Original assignee: GaMa Srl
Current assignee: GaMa Srl
Priority date: 2013-12-19
Filing date: 2014-12-19
Publication date: 2016-10-26
Also published as: WO2015092759A3; ITMI20132144A1; AR100301A1; WO2015092759A2

Abstract

An electric motor, comprises a stator (2) provided with stator windings (4), a rotor (3) provided with rotor windings (5) and electronic means for electronic switching. Advantageously said rotor windings define inductive elements for causing a rotor voltage drop (AVR) in the current circulating therein with respect to the supply voltage (VM) supplied thereto, said electronic means for electronic switching operating electrically in series with said rotor windings to work at a voltage (Vs) corresponding to the voltage (VM) with which said rotor windings (5) are supplied decreased by said rotor voltage drop (AVR), thereby allowing the use of low voltage electronic switching means.

Description

'Electric Motor'

DESCRIPTION

The present invention refers to an electric collector motor, particularly an electric collector motor for actuating the fan of an electrical apparatus such as a hair dryer apparatus and the like.

According to a further aspect, the present invention moreover refers to a method for managing the operation of an electric collector motor.

For the sake of simplicity, the present description is written in a non-limiting manner considering an electric motor that is intended to be used in a hair dryer apparatus.

As it is known, hair dryer apparatuses foresee, inside a containment body, for there to be electrical heating resistances that are positioned in an air duct, as well as a fan, which is actuated by an electric motor so as to ensure that, in the aforementioned duct, there is a suitable continuous flow of air that, after having been sucked from outside the hair dryer apparatus, is made to transit through said air duct before being discharged through an outlet opening.

In the aforementioned air duct the sucked air flow is heated by the aforementioned electrical resistances, which are generally made up of one or more resistive metal wires that are positioned in the aforementioned air duct. The dimensioning of the electrical resistances and the determination of their operation temperature are carried out by duly keeping the correct dynamic conditions of use, that is to say by considering the air flow rate that during normal operation of the hair dryer apparatus transits in the aforementioned air duct and therefore hits the electrical resistances positioned there, ensuring that there is the continuous cooling through heat loss.

In the aforementioned hair dryer apparatus, the fan is positioned in the rear part of the containment body, so that the electric motor is downwind with respect to the fan itself.

Usually, the fans used are of the centrifuge type or of the axial type, underlining that centrifuge fans are generally used in hair dryer apparatus intended for professional use, in which it is foreseen for universal motors to be used provided with stator and rotor windings that make it possible for there to be a direct supply of power from the mains but require the presence of suitable electrical and/or electronic components, for example condensers, which are suitable for operating with high voltage, in the order of 370- 400 Volts, thus being moreover penalised in terms of weight and bulk of the motor. The use of this type of motor is thus not very popular in hair dryer apparatus for home use which must have very small dimensions.

On the other hand, fans of the axial type are used in hair dryer apparatuses for use at home in combination with a continuous current motor. This type of motor requires a power supply circuit made up of a voltage-drop resistance branch and a diode bridge for rectifying from alternating current to continuous current .

With respect to the aforementioned universal motors, continuous current motors are cheaper, have much smaller dimensions and weigh less, even though all this is obtained at the expense of its lifetime. In particular, the thing that penalises the lifetime of collector motors the most is the problem of the sparking of the switching brushes .

Particularly for electrical apparatuses intended for an intense use over an extended time period, for example hair dryer apparatuses for professional use, the use of brushless motors has been proposed, with three-phase technology, considering the performance that such motors can offer, also in terms of lifetime. In particular, these motors foresee the replacement of the mechanical switch with a MOSFET circuit, i.e. with an electronic switch, which, when suitably driven by a generator circuit, provides for carrying out the switching necessary in order to produce the rotation of the magnetic field and therefore of the rotor.

On the other hand, the use of the aforementioned brushless motors is not particularly suitable for small household appliances that require being gripped and moved manually by the user. This is because the components that are implemented in such motors define a considerable increase in terms of weight and bulk of a brushless motor with respect to the other types of motors. Essentially, this is because these motors require:

- having to rectify the mains voltage, which makes it necessary to use high voltage power supply condensers, which are very bulky in addition to costly and

- an even number of pairs of high voltage mosfet which, having to operate with voltages of up to 400 Volts foreseen inside such motors, necessarily have high bulk and are quite costly.

For this purpose it is necessary to highlight that the use of condensers on the power supply in inlet, in order to lower the working voltage at which the mosfets operate is not particularly advantageous and does not solve the problems. This depends on the fact that the power supply condensers to be used at the inlet with high voltage foreseen must necessarily be large and therefore costly. Moreover, these types of condensers can lead way to undesired malfunctioning that can cause such condensers to explode.

Considering what has been described above, it is clear how nowadays there is a strong need to have electric motors that perform better in terms of lifetime and performance, despite having smaller dimensions and weight so as to be easily housed even inside small household appliances such as a hair dryer apparatus and the like.

The problem forming the basis of the present invention is that of devising an electric collector motor which has structural and functional characteristics such as to satisfy the aforementioned need, at the same time avoiding the drawbacks mentioned with reference to the prior art.

Such a drawback is solved with an electric collector motor in accordance with claim 1.

According to a further aspect such a drawback is solved also with a method for managing the operation of an electric collector motor in accordance with claim 10.

Further characteristics and advantages of the electric motor according to the present invention shall become clearer from the following description of a preferred embodiment thereof, given as an indication and not for limiting purposes, with reference to the attached figures, in which:

- figure 1 shows the wiring scheme of a single phase electric motor according to the invention,

- figure 2 shows the wiring scheme of a two phase electric motor according to the invention and

- figure 3 represents a partial perspective view of the stator of the motor according to the invention with some laminations of the stator pack that are exploded .

With reference to the attached figures, the electric motor according to the present invention is generally indicated with reference numeral 1.

More specifically, the electric motor 1 is a motor that is intended for being used in a hair dryer apparatus [not illustrated] so as to set in rotation a fan for sucking air, being it moreover possible to foresee the use of such a motor in small household appliances of other kinds. The hair dryer apparatus comprises a containment body inside which an air duct extends between an air suction opening and a sucked air discharge opening.

Inside the aforementioned air duct there is a suction fan that is actuated by the aforementioned electric motor 1 arranged downstream of the suction fan .

Such a suction fan, when it is set in rotation by the electric motor 1, is suitable for generating an air flow inside the aforementioned containment body between the suction opening and the discharge opening.

Inside the aforementioned air duct, more precisely between the electric motor 1 and the aforementioned air discharge opening, there are electric heating means, for example made up of one or more resistive metal wires, which are suitable for generating the amount of heat necessary in order to heat the transiting flow in the aforementioned duct and being expelled through the aforementioned air discharge opening.

Concerning now the electric motor 1, this comprises :

- a stator 2;

a rotor 3 that is rotatably supported in rotation inside said stator 2 ; stator windings 4 associated with the stator 2 so as to generate a stator magnetic field;

- rotor windings 5 that are associated with the rotor 3 for generating a rotor magnetic field, as well as

- electronic means for electronic switching 7.

Advantageously, the aforementioned rotor windings

5 and the aforementioned stator windings 4 define inductive elements for causing a rotor voltage drop AV_R and, respectively, a stator voltage drop AV_S in the current circulating therein with respect to the supply voltage V_M with which said rotor windings 5 and said stator windings 4 are supplied and:

the aforementioned electronic means for electronic switching operate in electrical series with the aforementioned rotor windings 5 to be supplied with the current flowing through said rotor windings 5 and thus to operate at a voltage V_s corresponding to the voltage V_M with which said rotor windings 5 are supplied decreased by said rotor voltage drop AV_R, thereby allowing the use of low voltage electronic switching means or, alternatively,

the aforementioned electronic means for electronic switching operate in electrical series with the aforementioned stator windings 4 so as to be supplied with the current flowing through said stator windings 4 and to thus operate at a voltage V_s corresponding to the voltage V_M with which said stator windings (4) are supplied decreased by the aforementioned stator voltage drop AV_S, thereby allowing the use of low voltage electronic switching means .

Preferably, the aforementioned rotor windings 5 that are associated with the rotor 3 are supplied in alternating current AC from the electric mains at a predetermined mains voltage V_M through unswitched wiping contacts, whereas the aforementioned electronic means for electronic switching carry out an electronic switching of the current for said stator windings 4 that are associated with the stator 2.

Preferably, the aforementioned rotor windings 5 that are associated with the rotor 3 are directly supplied in alternating current AC from the electric mains at the predetermined mains voltage V_M through unswitched wiping contacts, without therefore foreseeing there to be condensers or other elements for reducing the voltage applied to the inlet of said rotor windings 5.

The aforementioned electronic means for electronic switching 7 reverse the stator magnetic field in a manner corresponding to every cyclical reversal of the rotor magnetic field defined by the phase inversions of the supply current coming from the mains with which the rotor windings 5 are supplied.

With reference to the aforementioned electronic means for electronic switching it is worth highlighting that these comprise transistor switching means 7, preferably MOSFET.

With reference to the motor 1 that is illustrated in figure 1, it is worth highlighting that it is of the single phase type and it foresees a pair of MOSFETs for a single phase synchronous mode.

figure 2 refers to a two phase using two pairs of MOSFET for a two phase synchronous modality.

In accordance with the invention, the method for managing the operation of an electric motor of the type that has been previously described comprises the steps of:

- supplying the aforementioned rotor windings 5 that are associated with the rotor 3 at a predetermined mains voltage V_M so as to generate a rotor magnetic field;

- supplying the aforementioned stator windings 4 that are associated with the stator 2 at a predetermined mains voltage V_M so as to generate a stator magnetic field,

in which:

- the rotor windings 5 define inductive elements for causing a rotor voltage drop AV_R in the current circulating therein with respect to supply voltage V_M supplied thereto and

- the stator windings 4 define inductive elements for determining a stator voltage drop AV_S in the current circulating therein with respect to supply voltage V_M supplied thereto,

and in which:

- the electric motor 1 comprises electronic means for electronic switching that operate in electrical series with the aforementioned rotor windings 5 to be supplied with the current flowing through said rotor windings 5 and thus for operating at a voltage V_s corresponding to the voltage V_M with which said rotor windings 5 are supplied decreased by the rotor voltage drop AV_R, thereby allowing the use of low voltage electronic switching means or, alternatively,

said electric motor (1) comprises electronic means for electronic switching that operate in electrical series with said stator windings 4 for being supplied with the current flowing through said stator windings 4 and thus for operating at a voltage V_s corresponding to the voltage V_M with which said stator windings 4 are supplied decreased by said stator voltage drop AV_S, thereby allowing the use of low voltage electronic switching means.

Preferably, in accordance with the embodiment illustrated in the schemes of figures 1 and 2, the aforementioned rotor windings 5 that are associated with said rotor 3 are supplied in alternating current AC from the electric mains to a predetermined mains voltage V_M through unswitched wiping contacts and the aforementioned electronic means for electronic switching carry out an electronic switching of current for said stator windings 4 that are associated with the stator 2.

Preferably, the aforementioned electronic means for electronic switching 7 carry out a cyclical reversal of the stator magnetic field in a manner corresponding to each cyclical reversal of the rotor magnetic field determined by the phase reversals of the supply current coming from the mains with which the rotor windings 5 are supplied.

Preferably, the aforementioned stator windings 4 associated with the stator 2 are directly supplied in alternating current AC from the electric mains to the predetermined mains voltage V_M. From what has been described above, the motor according to the invention, just like the method according to the invention for managing an electric motor, make it possible to satisfy the previously highlighted requirement.

Indeed, the motor according to the invention makes it possible to satisfy the aforementioned requirement by using a mixed system, in which the rotor supply brushes define unswitched wiping contacts that are capable of carrying out only the function of electrically connecting/supplying the rotor windings, since the switching is carried out by a pair of mosfets for a single phase synchronous modality or by many pairs of mosfets for motors with many phases.

The technical solution that is implemented in the electric motor 1 according to the invention:

- makes it possible to achieve a considerable reduction of electronic components, and

does not require the use of electronic components sized to operate with high operation voltage, since the rotor winding, provides for reducing the voltage towards the electronic circuit arranged downstream in electrical series.

In accordance with the embodiment shown in figure 3, the stator 2 is formed by a plurality of stator laminations 21 that are assembled together so as to form a stator pack.

Such stator laminations 21 have a perimeter profile comprising perimeter projecting portions 22 and perimeter recessed portions 23 with respect to the axis of the stator 2. Advantageously, at least two stator laminations 21 of said stator pack are positioned so that for first perimeter projections 22 of a first stator lamination 21 there are corresponding perimeter recesses 23 of a second stator lamination, said first perimeter projections 22 of the first stator lamination 21 define a perimeter finning in said stator pack to increase the heat dissipation.

Preferably, the contiguous stator laminations 21 of said stator pack are positioned so that first perimeter projections 22 of a stator lamination correspond to perimeter recesses 23 of the contiguous stator lamination 23, substantially as represented in figure 3.

In the operation of the electric motor according to the invention, since the rotor windings are not subjected to the work of the switching mosfet, but are freely set in series with the circuit of the mains at 50 or 60Hz, perform the dual function of dropping the voltage and of generating the rotor magnetic field. This magnetic field will obviously be alternated like the main power supply, but it is necessary to consider that, as previously described, the driving circuit of the MOSFET provides, at the same time, for cyclically reversing also the stator field, which provides for the rotation of the magnetic field, as well as the reversal of the polarity of the mains frequency. The main advantages that can be achieved with the electric motor according to the invention are:

- it is not necessary for there to be electronic components that are suitable for operating with high voltage;

- the rotor part operates in alternating current, therefore it is not required for there to be any large stabilising condenser;

- the wiping contacts for supplying the rotor, do not carry out the switching function, avoiding the drawback of the limited lifetime over time and

- the structural simplification carried out makes it possible to integrate the electronic parts inside the motor without the bulk of the motor being penalised.

Of course, a man skilled in the art, with the purpose of satisfying contingent and specific requirements, can carry out numerous modifications and variants to the electric motor described above, all moreover belonging to the scope of protection of the invention as defined by the following claims.

So, for example, it is possible to foresee an electric motor with many phases, for example with a three phase electric motor, just like it is possible to make a motor having more than two magnetic poles.

^■k * * * * * *

Claims

1. An electric motor, comprising:

- a stator (2 ) ;

- a rotor (3) rotatably supported to rotate in said stator (2);

- stator windings (4) associated with said stator

(2) for generating a stator magnetic field;

- rotor windings (5) associated with said rotor

(3) for generating a rotor magnetic field;

- electronic means for electronic switching,

characterized in that:

said rotor windings (5) and said stator windings (4) define respective inductive elements for causing a rotor voltage drop (AV_R) and respectively a stator voltage drop (AV_S) in the current circulating therein with respect to the supply voltage (V_M) supplied thereto,

wherein :

- said electronic means for electronic switching operate electrically in series with said rotor windings (5) to be supplied with the current flowing through said rotor windings (5) , to work at a voltage (V_s) corresponding to the voltage (V_M) supplied to said rotor windings (5) decreased by said rotor voltage drop (AV_R) , thereby allowing the use of low voltage electronic switching means or, alternatively,

- said electronic means for electronic switching operate electrically in series with said stator windings (4) to be supplied with the current flowing through said stator windings (4), to work at a voltage (V_s) corresponding to the voltage (V_M) supplied to said rotor windings (5) decreased by said stator voltage drop (AV_S) , thereby allowing the use of low voltage electronic switching means.

2. An electric motor as claimed in claim 1, wherein:

- said rotor windings (5) associated with said rotor (3) are supplied with an alternating current AC from the mains at a predetermined mains voltage (V_M) through unswitched wiping contacts;

- said electronic means for electronic switching provide electronic switching of current for said stator windings (4) associated with said stator (2).

3. A motor as claimed in claim 1 or 2, wherein said rotor windings (5) associated with said rotor (3) are directly supplied with an alternating current AC from the mains at a predetermined mains voltage (V_M) through unswitched wiping contacts.

4. A motor as claimed in any of claims 1 to 3, wherein said electronic means for electronic switching (7) reverse the stator magnetic field in accordance with each cyclic reversal of the rotor magnetic field, as caused by the phase reversals of the mains supply current supplied to the rotor windings (5).

5. A motor as claimed in claim 1, wherein said stator windings (4) associated with said stator (2) are directly supplied with an alternating current AC from the mains at a predetermined mains voltage (V_M) .

6. A motor as claimed in any of claims 1 to 5, wherein said electronic means for electronic switching include transistor switch means (7).

7. An electric motor as claimed in claims 1 to 5, wherein said electronic means for electronic switching include MOSFET (7) .

8. A multi-pole electric motor as claimed in any of claims 1 to 7, wherein:

- said stator (2) is made up of a plurality of stator laminations (21) assembled together into a stator pack;

- said stator laminations (21) have a perimeter profile comprising projecting perimeter portions (22) and recessed perimeter portions (23) , and

- at least two stator laminations (21) of said stator pack are in such positions that first perimeter projections (22) of a first stator lamination (21) correspond to perimeter recesses (23) of a second stator lamination (21) , said first perimeter projections (22) of said first stator lamination (21) defining perimeter fins in said stator pack for increased heat dissipation.

9. A multi-pole electric motor as claimed in claim 8, wherein contiguous stator laminations (21) of said stator pack are in such position that first perimeter projections (22) of a stator lamination (21) correspond to perimeter recesses (23) of the contiguous stator lamination (21).

10. A method of operation of an electric motor, comprising the steps of:

- providing an electric motor as claimed in any of claims 1 to 9,

- powering said rotor windings (5) associated with said rotor (3) with a preset voltage (V_M) for generating a rotor magnetic field;

- powering said stator windings (4) associated with said stator (2) with a preset voltage (V_M) for generating a stator magnetic field,

characterized in that:

said rotor windings (5) define inductive elements for causing a rotor voltage drop (AV_R) in the current circulating therein with respect to the supply voltage (V_M) supplied thereto and said stator windings (4) define inductive elements for causing a stator voltage drop (AV_S) in the current circulating therein with respect to the supply voltage (V_M) supplied thereto,

wherein :

- said electric motor (1) comprises electronic means for electronic switching which operate electrically in series with said rotor windings (5) to be supplied with the current flowing through said rotor windings (5) and to work at a voltage (V_s) corresponding to the voltage (V_M) supplied to said rotor windings (5) decreased by said rotor voltage drop (AV_R) , thereby allowing the use of low voltage electronic switching means or, alternatively,

- said electric motor (1) comprises electronic means for electronic switching which operate electrically in series with said stator windings (4) to be supplied with the current flowing through said stator windings (4) to work at a voltage (V_s) corresponding to the voltage (V_M) supplied to said stator windings (4) decreased by said stator voltage drop (AV_S) , thereby allowing the use of low voltage electronic switching means.

11. A method as claimed in claim 10, wherein:

12. A method as claimed in claim 10 or 11, wherein said rotor windings (5) associated with said rotor (3) are directly supplied with an alternating current AC from the mains at the predetermined mains voltage (V_M) through unswitched wiping contacts.

13. A method as claimed in claim 10, wherein said stator windings (4) associated with said stator (2) are directly supplied with an alternating current AC from the mains at a predetermined mains voltage (V_M) .

14. A method as claimed in any of claims 10 to 13, wherein said electronic means for electronic switching (7) provide cyclic reversal of the stator magnetic field in accordance with each cyclic reversal of the rotor magnetic field, as caused by the phase reversals of the mains supply current supplied to the rotor windings ( 5 ) .