WO2019144203A1

WO2019144203A1 - Stator with ventilation ducts for electric machine

Info

Publication number: WO2019144203A1
Application number: PCT/BG2018/000037
Authority: WO
Inventors: Encho Nikolov Popov
Original assignee: Almott Ood
Current assignee: Almott Ood
Priority date: 2018-01-24
Filing date: 2018-10-04
Publication date: 2019-08-01
Anticipated expiration: 2020-07-24
Also published as: BG67198B1; BG112668A

Abstract

The stator with ventilation ducts for an electric machine finds application in generators and electric motors whereas provides increased power and reduces their temperature without increasing the dimensions of the electric machine. The stator (9) includes a stator pack (10) with a plurality of slots (11), formed on its inner surface in which a winding (12) is laid. Concentrically over the winding (12), at least one circle ventilation ducts (13, 21) is formed which have over 50% increased area of their internal surface due to their shaping as a hollow four-walled body made up of two pairs of opposing walls (a1, a2 and b1, b2). Each of these pairs of opposing walls (a1, a2 and b1, b2) of each ventilation duct (13, 21) is formed of alternately one after the other oval concave (23) and convex (22) surfaces with total amplitude (A), which does not exceed 2 mm.

Description

STATOR WITH VENTILATION DUCTS FOR ELECTRIC MACHINE

TECHNICAL FIELD

The invention relates to a stator with ventilation ducts for an electric machine with increased power with cooling by a fan, designed to work as an alternator for charging storage batteries, as ah induction motor, as an electric motor for vehicles propulsion, as servomotors.

PRIOR ART

A stator with axial ventilation ducts mounted in alternator with air cooling by a fan is known [1], including stator pack with multiple slots on its inner surface in which a winding is laid over which at least one circle ventilation ducts is concentrically formed.

This solution has the disadvantage that the power of the electric machine with such a stator is reduced and its life is shortened. This is due to the fact that the area of the internal heat release surface of the air ducts is limited, thereby heat transfer from stator pack to the air passing through the ducts is limited, which leads to that the temperature of the working parts of the electric machine is increased. The increase of heat release surface by magnification the diameter of the ductc is limited as it leads to an increase in the dimensions of the electric machine. Furthermore, the increase in the diameter of the ventilation ducts leads to reducing the movement speed of the passing air. As a result of reduced airspeed, the coefficient of heat transfer from the surface of the ventilation ducts is reduced.

SUMMARY OF THE INVENTION

The aim of invention is to increase the power of the electric machine and reduce the temperature without increasing of its dimensions.

The aim of invention is solved by a stator with ventilation ducts for an electric machine including a stator pack with multiple slots on its internal surface in which a winding is laid over which at least one circle ventilation ducts is concentrically formed. According to the invention, each ventilation duct is formed as a hollow four-wall body made up of two pairs of opposing walls al, a2 and bl, b2. Each of these pairs of opposing walls al, a2 and bl, b2 of each ventilation duct is formed by alternating one after the other oval concave and convex surfaces that have in axial direction local radii R2 greater than 0.3 mm. Amplitude value A of the sum of the height hi of the convex surface and the height h2 of the concavity of the concave surface is less than 2 mm. The concave and convex surfaces located on two opposite walls of the ventilation holes are formed so that against each concave surface on one of the walls al, bl of the duct there is a corresponding convex surface on the other opposite wall a2, b2. Every two adjacent walls al, a2 and bl, b2 of each ventilation duct at the point of contact forms a chute with a radius R1 less than 2 mm.

It is possible, in transitions between convex and concave duct surfaces planar surfaces with radial size X which is less than 0.5 mm to be shaped.

It is possible that the stator pack to be enveloped by a housing, whose inner surface acts as one of the walls b2 of the duct from the outermost circle of ventilation ducts toward the winding.

An advantage of the stator with ventilation ducts for electric machine according to the invention is the increased power of the electric machine and its reduced temperature without increasing of its dimensions, due to the fact that the area of the formed cooling surface of the ducts towards the smooth cylindrical surface of the known closest technical solution is increased by over 50% without duct sizes to be increased and without the speed of air movement in the ventilation ducts to be reduced. So, at saved cooling ducts sizes the dimensions of the electrical machine in which the stator according to the invention is built in are not increased.

Another advantage is, that the small sizes and mutual location of the concave and convex surfaces of the duct walls, practically, do not necessitate an increase in the cross dimension of the yoke of the stator pack, or the dimensions of the electric machine. Thus, the magnetic resistance of the stator is practically not increased compared to the yoke with smooth cylindrical ducts. As a result of that, the temperature of the parts of the electric machine has been reduced and the power of the electric machine has been increased without increasing the dimensions of the electrical machine as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

Fig.l represents a longitudinal section of the electric machine with a stator with ventilation ducts according to the invention with one circle ventilation ducts formed in the yoke of the stator pack.

Fig.2 represents a cross-section of a stator set without a housing according to the invention with one circle ventilation ducts.

Fig.3 represents a cross-section of a stator set with ventilation ducts with housing according to the invention with two circles of ventilation ducts.

Fig.4 represents cut-out of a cross section of a stator set with ventilation ducts without housing according to the invention with one circle ventilation ducts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 shows an alternator with a stator with ventilation ducts, according to the invention, comprising a shaft 1 supported by a front bearing 2 and rear bearing 3 in front end bell 4 and rear end bell 5. Attached to shaft 1 rotor 6 is fixed. To the end bells, a front exciter 7 and rear exciter 8 are fastened.

In another embodiment of the invention not shown in FIG. 1, the exciter may be mounted in the rotor.

Between the end bells 4 and 5 a stator set 9 is pressed. The stator set 9 includes a stator pack 10. On the inner surface of the stator pack 10, a plurality of slots 11 is formed in which a winding 12 is laid. In the stator pack yoke 10 air cooling ducts 13 are formed through which air 14 is driven by a fan 15. The alternator is connected to a storage battery by terminals 16 and 17.

Figure 2 is a cross-sectional view of a stator set 9 with stator pack 10 for an electric machine according to the invention, with one concentric circle of air-cooling ducts 13.

Figure 3 is a cross-sectional view of a stator set 18 with a housing 19, in which a stator pack 20 is stationary secured. In the stator pack 20 two concentric circles of air-cooling ducts, according to the invention are formed. They are a first concentric circle of ventilation ducts 13 located above the winding 12 and a second concentric circle ventilation ducts 21 located above the first concentric circle ducts and directly below the housing 19. Fig. 4 shows the structure of the cooling surface in the ventilation ducts according to the invention in a partial cut-out of the stator set 9 with one concentric circle of ventilation ducts 13, according to the invention. Each ventilation duct 13 is formed as a hollow four- all body made up of two pairs of opposing walls al, a2 and bl, b2. Each of these pairs of opposing walls al, a2 and bl, b2 of each ventilation duct 13 is formed by alternately one after the other oval concaves 23 and convex 22 surfaces which in the axial direction have local radii R2 greater than 0.3 mm, and amplitude value A of the sum of the height hi of the convex surface

22 and the height h2 of the concavity of the concave surface 23 is less than 2 m . The concave

23 and convex 22 surfaces located on two opposing walls of the ventilation holes 13 are formed so that against each concave surface 23 on one of the walls al, bl of the duct 13 is a corresponding convex surface 22 on the other opposite wall a2, b2. Each two adjacent walls al, a2 and bl, b2 of each ventilation duct 13 at the point of contact form a chute with a radius R1 less than 2 mm.

As an embodiment of the invention, in the transition zones from the concaves 23 to the convexities 22 planar surfaces of lengths X are formed.

It is possible for the stator pack 10 to be enveloped immovably by a housing 1, the inner surface of which acts as one of the walls b2 of the duct from the outermost toward the winding 12 circuit of ventilation ducts 21.

USE OF THE INVENTION

The stator with ventilation ducts 13, 21 according to the invention, is used as it is embedded in an electric machine. The electric machine comprises a shaft 1 with rotor 6 immovably fixed to the shaft 1. In the rotor 6 exciter 7, 8 is built-in.

It is possible that the exciters are fixed to the front 4 and rear 5 end bells of the electric machine. The shaft 1 is supported by front 2 and rear 3 bearings in front 4 and rear 5 end bells. Between the front 4 and the rear 5 end bells a stator 9 with ventilation ducts 13, 21 is pressed according to the invention. Stator 9, according to the invention, has improved cooling due to the structure of the ventilation ducts 13, 21. As a consequence of the improved cooling, the power of the electrical machine is increased, and the temperatures are reduced.

EXPERIMENTAL RESULTS RECEIVED BY SAMPLE INVESTIGATION REALISING THE INVENTION The invention has experimented with an alternator 535A, 28Y. The comparison was made with a previous version of the same alternator with a stator with two concentric circles whose ventilation ducts are formed according to Fig. 4, hut with smooth inner surfaces of the ducts. After changing only the tool, with which the ventilation ducts are punched in order to be manufactured according to the invention, the temperature of the stator winding 12 is reduced by 18°C. After experimenting with another embodiment, while preserving the previous winding temperature, the current is increased by 9% (48 A).

CITED DOCUMENTS

1. DELSTAR-HD ALTERNATOR-400 SERIES, www.DIXIE ELECTRIC.COM

Claims

1. Stator with ventilation ducts for an electric machine including a stator pack with multiple slots on its internal surface in which a winding is laid over which at least one circle ventilation ducts is concentrically formed, characterized in that each ventilation duct (13, 21) is formed as a hollow four- wall body made up of two pairs of opposing walls (al, a2 and bl, b2) and each of these pairs of opposing walls (al, a2 and bl, b2) of each ventilation duct (13, 21) is formed by alternating one after the other oval concaves (23) and convex (22) surfaces that have in axial direction local radii (R2) greater than 0.3 mm, and amplitude value (A) of the sum of the height (hi) of the convex surface (22) and the height (h2) of the concavity of the concave surface (23) is less than 2 m whereas concavities (23) and convex (22) surfaces located on the two opposite walls of the ventilation holes (13, 21) are formed in such a way that against each concave surface (23) on one of the walls (al, bl) of the duct (13, 21) there is a corresponding convex surface (22) on the other opposite wall (a2, b2), and every two adjacent walls (al, a2 and bl, b2) of each ventilation duct at the point of contact forms a chute with a radius (Rl) less than 2 mm.

2. Stator with ventilation ducts for an electric machine according to claim 1, wherein in the transition zones from the convex (22) to the concave (23) surfaces of the duct (13, 21) are formed planar surfaces with radial size (X) which is less than 0,5 him.

3. Stator with ventilation ducts for an electric machine according to claims 1 and 2, wherein the stator pack (10) is enveloped stationary by a housing (19), whose inner surface acts as one of the walls (b2) of the duct from the outermost circle of ventilation ducts (21) toward the winding (12).