GB2047130A - Method of assembling stator core of electric machine inside the housing thereof - Google Patents

Abstract

A method of assembling a stator core 1 of an electric machine inside the housing 2 thereof comprises securing of resilient coupling ribs 3 with their springing portions 6 to the housing, the springing portions of the ribs being previously urged against core supporting portions 5 of the ribs up to an elastic deformation state by means of detachable clamping members (bolts 7 in holes 8) (Figures 2,3), assembling of core segments on the core supporting portions 5 of the resilient coupling ribs 3, compressing of the core segments, securing them under compression to the ribs, and removing of the detachable clamping members when the core is secured to the resilient coupling ribs. The resilience of ribs 3 is provided by slots 4. <IMAGE>

Description

SPECIFICATION Method of assembling stator core of electric machine inside the housing thereof The present invention relates to electric machines and more particularly to methods of assembling a stator core of an electric machine inside the housing thereof. Most advantageously the invention can be used in large electric machines, such as turbo generators.

According to the invention there is proposed a method of assembling a stator core of an electric machine inside the housing, comprising securing of resilient coupling ribs having springing portions and core supporting portions to the housing with their springing portions, assembling of core segments on the core supporting portions of the ribs, compressing of the core segments and securing them under compression to the ribs, wherein according to the invention, prior to securing the resilient coupling ribs to the housing, their springing portion are urged against the core supporting portions up to an elastic deformation state by means of detachable clamping members which are removed when the core segments are secured to the resilient coupling ribs.

The proposed method of assembling a stator core of an electric machine on resilient coupling ribs previously pressed up to a state of elastic deformation provides a tight fit of the core on the ribs, since, when the clamping members are removed, the springing portions of the ribs tend to straighten, thus providing a constant pressing of the ribs against the core. The tight fit of the core on the resilient coupling ribs eliminates developing of clearances between the ribs and the core during operation of the electric machine, which leads to decrease in wear of the ribs and in noise of the operating machine.

The invention is further explained by a detailed description of its embodiment with reference to the accompanying drawings, in which: Figure 1 shows a stator core of an electric machine, assembled inside the housing, longitudinal section.

Figure 2 is an eniarged view of the resilient coupling rib for supporting the stator core, shown in Figure 1, inside the housing, in accordance with the invention, and Figure 3 shows a cross section along the line Ill-Ill of Figure 2.

A core 1 (Figure 1) of a stator of an electric machine is supported in a housing 2 by means of resilient coupling ribs 3 extending in parallel to the stator axis and equally spaced around the periphery of the core 1 to compress it symmetrically. The coupling ribs 3 have longitudinaily milled through slots 4 imparting resilience to the ribs 3 and forming in the body of the rib 3 a core supporting, or radially inner portion 5, and a springing, or radially outer portion 6.

Assembling to the core 1 of the stator inside the housing 2 of the electric machine, according to the invention, is erformed as follows. Initially, the springing portions 6 of the ribs 3 are urged by means of detachable clamping members towads the core supporting portions 5 up to a state of elastic deformation. Such clamping members in the described embodiment of the invention are bolts 7 (Figure 2) which are positioned into bores 8 drilled in the ribs 3, the bores 8 having threaded portions only in the core supporting portion 5 of the ribs 3. The springing portions 6 of the ribs 3 are bent and displaced towards the core supporting portions 5.

To provide the urging of the spring portions 6 of the ribs 3 towards the core supporting portions 5 other kinds of detachable clamping members can be used, such as clamps, which are mounted on the sides of the ribs 3 along their slot portions. In that case there is no need in drilling the threaded bores 8 intheribs3.

The resilient ribs 3 accommodating the bolts 7 are secured with their springing portions 6 to annular walls 9 (Figure 1 ) of the housing 2 by means of, e.g., joint angles 10 and weldings 11. Then, at one end face of the housing 2 a clamping plate 13 is mounted on cylindrical threaded end portions 12 of the ribs 3 and is secured by nuts 14.

The core supporting portions 5 of the ribs 3 are provided with keys 15 (Figure 3) of dovetail type arranged along the length of the segments of the core 1 (Figure 1), said keys facing the stator axis. A certain number of segments of the core 1 are mounted on said keys, the segments having appropriate slots (not shown) to receive the keys. The segments of the core 1 are then compressed under specific pressure of 10 to 12 kg/sq cm. Furtheron, on the ribs 3 are similarly mounted in succession and compressed other parts of the segments of the core 1 until the whole of the core is assembled, the specific pressure being increased with every compression.

At the other end of the housing 2 a second clamping plate 13 is mounted on the threaded portions 12 of the ribs 3, and a final compression of the segments of the core 1 together with the clamping plate 13 is carried out, the specific pressure being in the range from 17 to 20 kg/sq cm. The segments of the core 1 are secured under pressure to the ribs 3 by the nuts 14.

Then the bolts 7 (Figure 2) are screwed out from the ribs 3. To gain access to the bolts 7 in the assembled core 1 (Figure 1) the annular walls 9 of the housing 2 are provided with openings 16.

After the bolts 7 are removed, the ribs 3 secured to the walls 9 (Figure 1) of the husing 2 tend to straighten the slot 4 and to displace in radial direction towards the stator axis, as a result of which the coe supporting portions 5 of the ribs 3 are forced against the bottoms of the slots (not shown) of the segments of the core 1, esigned to receive the dovetail keys 15 (Figure 3), and provide a tight fit of the core 1 (Figure 1) on the ribs 3. A tight fit of the core 1 on the ribs 3 ensures a uniform functioning of the ribs 3 during operation of the electric machine.

The amount of pressing of the ribs 3 against the core 1 and the respective bending of the springing portions 6 of the ribs 3 are chosen so as, from the one hand, to provide an elastic deformation of the springing portions 6 of the ribs 3 and, from the other hand, to eliminate the loosening of the ribs 3 during operation of the electric machine.

Thus, due to pre-stressing of the springing portions 6 of the ribs 3 to elastic deformation state by means of the detachable clamping members 7 (Figure 2) prior to fixing the ribs 3 inside the housing 2 (Figure 1 ) and removal of the clamping members 7 (Figure 2) after securing the core 1 inside the housing 2, a tight fit of the ribs 3 in the core 1 is provided, thus preventing the core 1 from loosening of the fit during operation of the electric machine and resulting in an increase in the electric machine, reliability.

Claims (4)

1. A method of assembling a stator core of an electric machine inside the housing thereof, comprising securing of resilient coupling ribs having springing portions and core supporting portions to the housing with their springing portions, assembling of core segments on the core supporting portions of the ribs, compressing of the core segments and securing them under compression to the ribs, wherein prior to securing the resilient coupling ribs to the housing, their springing portions are urged against the core supporting portions up to an elastic deformation state by means of detachable clamping members which are removed when the core segments are secured to the resilient coupling ribs.

2. A method of assembling a stator core of an electric machine inside the housing thereof performed substantially as hereinbefore described with reference to the accompanying drawings.

3. An electric machine having a stator core assembled according to claim 1 or claim 2.

4. An electric machine as claimed in claim 3 and substantially as herein described with reference to the accompanying drawings.