SQUIRREL CAGE ROTOR

Abstract

A squirrel cage rotor, is made up of a shaft, a rotor laminated core with rotor bars which are arranged in the interior, and short-circuiting rings with clearances through which the bar ends of the rotor bars extend out of the rotor laminated core. The rotor bars, on their surface, at least partially have an electrical insulation layer, wherein the electrical insulation layer is cohesively connected only to the surface of the rotor bars. The squirrel cage rotor is intended, in particular, for use in an asynchronous machine.

Claims

1. Squirrel cage rotor for an asynchronous machine, comprising a shaft, a rotor laminated core with rotor bars which are arranged in the interior, and short-circuiting rings with clearances through which the bar ends of the rotor bars extend out of the rotor laminated core, characterized in that the rotor bars, on their surface, at least partially have an electrical insulation layer, and in that the electrical insulation layer is cohesively connected only to the surface of the rotor bars.

2. Squirrel cage rotor according to claim 1, characterized in that at least one part of a short-circuiting ring consists of a disk stack which is constructed in a layered manner from disks with clearances.

3. Squirrel cage rotor according to claim 2, characterized in that the bar ends are electrically conductively joined to the disk stack of a short-circuiting ring.

4. Squirrel cage rotor according to claim 1, characterized in that the thickness of the insulation layer on the surface of a rotor bar is between 0.05 and 0.25 mm.

5. Squirrel cage rotor according to claim 1, characterized in that the surface portions of the bar ends, which extend out of the rotor laminated core, of the rotor bars do not have an electrical insulation layer.

6. Squirrel cage rotor according to claim 1, characterized in that only the radially outer and/or the radially inner surface area portions of a rotor bar have an electrical insulation layer.

7. Squirrel cage rotor according to claim 1, characterized in that the electrical insulation layer consists of an adhesive tape with a thickness of 0.05 to 0.15 mm.

8. Squirrel cage rotor according to claim 1, characterized in that the electrical insulation layer consists of a polyimide adhesive tape.

9. Squirrel cage rotor according to claim 1, characterized in that the rotor bars exhibit torsion about a longitudinal axis which runs through the surface area center of gravity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Exemplary embodiments of the invention will be explained in more detail with reference to the schematic drawings.

[0034] In said drawings:

[0035] FIG. 1 schematically shows a side view of a squirrel cage rotor,

[0036] FIG. 2 shows a view of a rotor bar with an application apparatus,

[0037] FIG. 3 shows an oblique view of a ready-to-install rotor bar with a partially applied insulation layer,

[0038] FIG. 4 shows an oblique view of a rotor bar with a partial insulation layer which is interrupted in the longitudinal axis, and

[0039] FIG. 5 shows a front view of a twisted rotor bar.

DETAILED DESCRIPTION

[0040] Parts which correspond to one another are provided with the same reference symbols throughout the figures.

[0041] FIG. 1 schematically shows a side view of a squirrel cage rotor 1. In this state, the rotor laminated core 3 is positioned on the shaft 2, combined with two short-circuiting rings 5 with clearances 51 which terminate the rotor laminated rotor 3 at the end side. A plurality of rotor bars 4 are arranged in the interior of the laminated core 3 and the short-circuiting rings 5. The bar ends 41 of the rotor bars 4 protrude into clearances 51 of the short-circuiting rings 5 and terminate flush with the respectively outermost disk 6 of the disk stack 7. In this case, a disk stack 7 consists of four disks 6 which have joining gaps for cohesive connection of the short-circuiting rings 5. A joining connection 8, for example by welding or soldering, is realized in the joining gap.

[0042] FIG. 2 shows a view of a rotor bar 4 with an application apparatus 100 for an insulation layer 10. In this case, said application apparatus is an automatic application apparatus 100 for a polyimide adhesive tape reservoir which is located on adhesive tape rollers 101. Automatic unrolling of the adhesive tape from the adhesive tape rollers 101 takes place at a constant feed rate. The tensile force which is caused by the feeding of the adhesive tape which adheres to the semifinished product ensures the tape is autonomously pulled off from its respective adhesive tape roller 101 in the process. A possible way of matching the adhesive tape as insulation layer 10 to the shape of the rotor bar 4, without air pockets or similar faults which have a negative effect on the adhesive strength occurring here, has also been found.

[0043] Rotated pressure-application rollers 102 which are matched to the profile of the rotor bar 4 serve in order to guide the adhesive tape onto the rotor bar without faults. To this end, the radii and special shapes of a rotor bar 4 have been made as negative profiles in contact-pressure rollers 102 composed of plastic. In this case, the rollers are mounted such that they are driven by the feeding of the tape. Therefore, the coating is applied with as little material consumption as possible by the previously supplied adhesive tape. However, in order to stick the tape to the bar, pneumatic grippers can also be used for series production. A gripper of this kind given comprehensive insulation coating is outstandingly suitable particularly for the straight side faces of the rotor bar.

[0044] The adhesive tape can therefore be applied along a section of the rotor bar without the formation of bubbles. In this case, it is advantageous to optimize the coating with adhesive tape in respect of material used by way of only the radii of the rotor bar having adhesive applied. Here, the contact resistance is sufficiently high both when the rotor is vertical and when the rotor is horizontal.

[0045] FIG. 3 shows an oblique view of a ready-to-install rotor bar 4 with a partially applied insulation layer 10 over the entire length. This variant consists in coating the entire rotor bar 4 with the adhesive tape only at the curved surface regions.

[0046] FIG. 4 shows an oblique view of a rotor bar with a partial insulation layer 10 which is interrupted in the longitudinal axis. For the purpose of partial coating of the rotor bar, the adhesive tape is applied as insulation layer 10 only in sections, depending on the length to be coated of the rotor bar 4. The uncoated regions serve, in particular in the region of the bar ends 41, for the subsequent welding process and do not have to be treated further.

[0047] FIG. 5 shows a front view of a twisted rotor bar 4. Stack transverse currents can occur, in particular, on squirrel cage rotors which are produced in a slanted manner. This slanted arrangement is achieved by way of the entire laminated core being twisted about its rotation axis. On account of this process, the slots of the laminated core are also twisted, this in turn leading to a rotor bar also having to be matched thereto, that is to say likewise twisted. The view illustrated in FIG. 5 of a rotor bar 4 intended for a slanted squirrel cage rotor clearly shows torsion about the longitudinal axis A which runs through the surface area center of gravity. Knowledge about the behavior of the coating in the event of twisting of the bar is important specifically in respect of series production. Said information is used to make a decision as to whether the coating can be applied before twisting or whether this process has to take place after said twisting. A polyimide adhesive tape coating can also be applied after torsion of the rotor bar of far beyond 10, as is often customary in the case of the production of turned rotors, without faults, air pockets or cracks. Further checking of the contact resistance also shows that the adhesive tape continues to satisfy its insulation properties.

[0048] Preferred process sequences, from amongst which coating of the rotor bar is advantageous, are:

[0049] 1. after cleaning/before stamping

[0050] 2. after stamping/before twisting

[0051] 3. after twisting.

[0052] The particularly preferred time at which a coating process is integrated into the production operation is between cleaning and stamping to the desired length.

List of Reference Symbols

[0053] 1 Squirrel cage rotor

[0054] 2 Shaft

[0055] 3 Rotor laminated core

[0056] 4 Rotor bar

[0057] 41 Bar end

[0058] 5 Short-circuiting ring

[0059] 51 Clearance

[0060] 6 Disk

[0061] 7 Disk stack

[0062] 8 Joining connection

[0063] 10 Insulation layer

[0064] 100 Application apparatus

[0065] 101 Adhesive tape roller

[0066] 102 Pressure-application roller

[0067] A Longitudinal axis