WO2013135312A2

WO2013135312A2 - High speed magnetoelectric synchronous motor

Info

Publication number: WO2013135312A2
Application number: PCT/EP2012/066001
Authority: WO
Inventors: Nikolajs Levins; Jānis DIRBA; Ludmila LAVRINOVIČA; Vladislavs PUGAČEVS
Original assignee: Rīgas Tehniskā Universitāte; Fizikālās Enerģētikas Institūts
Priority date: 2012-03-13
Filing date: 2012-08-16
Publication date: 2013-09-19
Also published as: WO2013135312A3; LV14509A; LV14509B

Abstract

The invention relates to electrical engineering industry, more specifically, to high speed magnetoelectric synchronous motors. The offered motor contains an external rotor (1) with prismatic permanent magnets (2, 3, 4, 5) and a slotted stator (6) with slots (8) and m-phase winding (9) in the slots (8); the stator (6) being separated from the rotor (1) by an air gap (7); the prismatic permanent magnets (2, 3, 4, 5) are fixed in spaces between the poles (10, 11, 12, 13) at an angle from 10º to 15º against tangent planes (14) of the rotor's (1) inner surface in places (15), where spaces between the poles (10, 11, 12, 13) come out in the airgap (7), wherein magnetization direction of the magnets (2, 3, 4, 5) is perpendicular to the edges of spaces between the poles (10, 11, 12, 13). The air gap (7) between the stator (6) and rotor (1) has its narrowest parts in front of the centre of the poles (10, 11, 12, 13), but the widest – in front of the edges of the poles (10, 11, 12, 13), wherein the width (δ) of the air gap (7) depends on the arc angular size (α) secant from pole centre to the point under consideration at the boundary between the poles.

Description

HIGH SPEED MAGNETOELECTRIC SYNCHRONOUS MOTOR

Technical Field The invention relates to electrical engineering industry, more specifically, to electrical motors, which can be used in home appliances, including electric tools. This motor can be compatible with actuating mechanism, for example, electric hand plane.

Background Art

There are known AC or DC commutator motors used in electric tools (WO 2005/109611 Al, RU 2005101715 A). Commutator brush assembly of such motors does not allow ensuring sufficiently high level of operational reliability and long product life.

There are known synchronous motors with permanent magnets (CN 202014145 U and LV 13924 B). However fixing of magnets in the known solutions is not safe enough, especially in high speed motors.

There is known synchronous motor with prismatic-shaped permanent magnets placed in a concave poles and being magnetized in the radial direction (LV 14335 B). Permanent magnets used are expensive. Their fixing is not secure enough, and the location does not allow improvement of quality of the magnetic field in the air gap. Motors with such magnet position have increased vibration and stator losses.

Disclosure of Invention The aim of the invention is overcoming drawbacks of the prior art solutions, in particular, the motor specific torque increase as well as reduction of vibration and manufacturing cost.

The aim is achieved by the proposed high speed magnetoelectric synchronous motor containing an external rotor having small number of poles with prismatic permanent magnets and a slotted stator with m-phase anchor winding; the stator being separated from the rotor by an air-gap. According to the invention the prismatic permanent magnets are being placed in spaces between the poles, at a 10-15 degrees angle against tangent planes of the rotor inner surface, the tangent planes being set in places, where the spaces between the poles come out in air-gap. Magnetization direction of the magnets is perpendicular to the edges of spaces between the poles.

Reduction of vibration is achieved by creating uneven air-gap between the stator and rotor of the motor. The width (δ) of the air gap is defined according to the expression:

⁵ = ^_ndn sec(pa),

where is the minimum air-gap under the centre of the pole;

p is the number of pole pairs;

a is the angle of an arc from the centre of the pole to the point under consideration.

Brief Description of Drawings

Fig. 1 is a schematic top cross section view of the proposed motor,

Fig. 2 is a diagram of the air-gap and magnetic induction changes under the pole.

The invention is further described by Fig. 1 and Fig. 2.

High speed magnetoelectric synchronous motor contains an external rotor 1 (according to one embodiment - four-pole rotor) with prismatic permanent magnets 2, 3, 4, 5 and a slotted stator 6. The rotor 1 is separated from the slotted stator 6 by an air gap 7. M- phase winding 9, for example two-phase, is placed in the stator slots 8.

The magnets 2-5 are mounted in the spaces between the poles 10-13. The magnets are mounted at an angle γ from 10° to 15° against the tangent planes 14 of the rotor's 1 inner surface in the places 15, where spaces between the poles come out in the air-gap 7. Magnetization direction of the magnets 2-5 is perpendicular to the edges of spaces between the poles 10-13.

The air gap 7 between the stator 6 and rotor 1 of the motor is uneven. The narrowest parts of the air gap 7 are in front of the centre of the poles 10-13, but the widest - in front of the edges of the poles 10-13. In Fig. 1 the uneven air gap 7 is shown at one pole 13 by the dashed line 16. According to the invention, the width (δ) of the air gap 7 depends on the arc angular size a secant from pole centre to the point under consideration at the boundary between the poles: δ = δ^ sec( pa), where δ^ is the minimum air-gap under the centre of the pole; p is the number of pole pairs; a is the angle of an arc from the centre of the pole to the point under consideration.

In the centre of each pole 10-13 there is non-magnetic space 17 with an opening width equal to the stator slot 8 opening width.

The motor works as follows. When the supply voltage is applied to the stator 6 winding 9, m-phase current flows in the winding 9 and creates a rotating magnetic field. As a result of the interaction between the magnetic field and poles 10-13, electromagnetic torque is generated and the rotor 1 begins to rotate. The proposed motor can also work as a brushless DC motor, in this case the m-phase windings 9 are switched using signals from the rotor position sensor.

As shown in Fig. 1, the magnets 2-5 are fixed slantwise in the spaces between the poles 10-13.

Since each magnet 2-5 in such a location serves for two poles, the number of magnets can be decreases almost twice. As a result the permanent magnet and the entire motor's production costs are decreasing. The total motor's weight is also decreasing and hence increases the specific moment.

Use of the uneven air gap 7 having increasing width from the pole's centre to the pole's edges according to the expression δ = δ _η sec( pa), decreases high-order harmonics of the magnetic field and approximates the magnetic flux density distribution in the air-gap 7 to a sinusoidal function, which is not distorted by the transverse reaction of the anchor due to non-magnetic space 17 in the centre of each pole 10-13. This also increases the specific torque (Fig. 2).

The slantwise arrangement of the magnets 2-5 in the spaces between the poles 10- 13 allows to increase reliability and simplify magnet mounting, e.g. by means of glue.

Claims

1. A high speed magnetoelectric synchronous motor, containing an external rotor (1) with prismatic permanent magnets (2, 3, 4, 5) fixed in spaces between poles (10, 11, 12, 13) and a slotted stator (6) with slots (8) and m-phase winding (9) in the slots (8); the stator (6) being separated from the rotor (1) by an air gap (7), characterized in that the prismatic permanent magnets (2, 3, 4, 5) are fixed in spaces between the poles (10, 11, 12, 13) at an angle from 10° to 15° against tangent planes (14) of the rotor's (1) inner surface in places (15), where spaces between the poles (10, 11, 12, 13) come out in the air-gap (7), wherein magnetization direction of the magnets (2, 3, 4, 5) is perpendicular to the edges of spaces between the poles (10, 11, 12, 13).

2. The motor according to claim 1, characterized in that the air gap (7) between the stator (6) and rotor (1) is uneven - has its narrowest parts in front of the centre of the poles (10, 11, 12, 13), but the widest - in front of the edges of the poles (10, 11, 12, 13), wherein the width (δ) of the air gap (7) depends on the arc angular size a secant from pole centre to the point under consideration at the boundary between the poles according to the formula:

⁵ = ^ndn sec(pa),

where is the minimum air-gap under the centre of the pole;

p is the number of pole pairs;