FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003 As amended by the Patents
(Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
3-Phase slip ring motor
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR
Chatterjee Chayan, Crompton Greaves Limited, Machines 7 Division, D-5, Industrial Area MPAKVN, Mandideep - 462 046, Madhya Pradesh, India, an Indian national
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a 3-phase slip ring motor
BACKGROUND OF THE INVENTION
Slip ring motors are a class of AC induction motors having slip rings connected to the ends of the rotor windings. Slip rings are also called rotary electrical interfaces, rotating electrical connectors, collectors, swivels or electrical rotary joints. Slip ring motors are used to continuously transmit electrical power, signal or data from a stationary source to a rotating source or vise versa. Slip ring motors are available in a variety of configurations and termination types and find applications both as high tension and low tension motors. Slip ring motors are used, for instance, in fibrizors of sugar mills, various types of crushes and pumps, compressors, presses, belt conveyors, drive mechanisms or induced or forced draft fans.
A slip ring motor comprises a rotor mounted on a shaft and rotatably disposed within a stator. The shaft is rotatably held in a pair of end shields fitted at the ends of the stator and comprises a hollow tubular member having a plurality of radial ribs extending from the tubular member in radially spaced apart relationship with one another. A star and delta connection ring is disposed over the reinforcing ring. A rotor core is disposed over and mounted to the star and delta connection ring and is having rotor windings and jumper windings. The rotor windings are connected to the star and delta connection ring by rotor winding connection cables. The motor also comprises a pair of slip rings disposed outside the non-drive end of the shaft and mounted on the shaft and the jumper windings are connected to the slip rings by jumper winding

connection cables. The jumper winding connection cables extend over the star and delta connection ring and underneath the reinforcing ring and further extend through the space between each pair of adjacent radial ribs. The jumper winding connection cables extend through the hollow space in the tubular member via radial holes in the tubular member. In such a construction of the motor, the jumper winding connection cables are loose and sagging in the space between every two radial ribs. During operation of the motor due to rotation of the rotor, the jumper winding connection cables are subjected to vibration and rub against the edges of the star and delta connection ring and reinforcing ring and sidewalls of the radial holes in the tubular member. As a result, the insulation of the jumper winding connection cables get damaged and the cables are required to be replaced periodically thereby increasing the running cost of the motor. Failure to replace the cables in time may lead to shorting and damage the rotor and motor and reduce the life thereof.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a 3-phase slip ring motor comprising a rotor mounted on a shaft, wherein the shaft comprises a hollow tubular member having a plurality of radial ribs extending from the tubular member in radially spaced apart relationship with one another, a reinforcing ring mounted over the outer ends of the radial ribs and a star and delta connection ring disposed over the reinforcing ring and the rotor comprises a rotor core disposed over and mounted to the star and delta connection ring and having rotor windings and jumper windings, the rotor windings being connected to the star and delta connection ring by rotor winding connection cables and the jumper windings being connected to the slip rings by jumper winding

connection cables and wherein each of the jumper winding connection cables extends over the star and delta connection ring and underneath the reinforcing ring and through the space between each pair of adjacent radial ribs and through the hollow space in the tubular member via radial holes in the tubular member and wherein each of the jumper connection cables is supported in the space between each pair of adjacent radial ribs on a support means disposed between and fixed to each pair of adjacent radial ribs.
The following is a detailed description of the invention with reference to the accompanying drawings, in which the sole Fig 1 is a side or end view of the rotor of a 3-phase slip ring motor according to an embodiment of the invention. As illustrated in Fig 1 of the accompanying drawings, the rotor 1 is mounted on a shaft 2 which comprises a hollow tubular member 3 having a plurality of radial ribs 4 extending from the tubular member in radially spaced apart relationship with one another. A reinforcing ring 5 is mounted over the outer ends of the radial ribs. 6 is a star and delta connection ring disposed over the reinforcing ring. A rotor core 7 is disposed over and mounted to the star and delta connection ring with bracings 8 and is having rotor windings 9 and jumper windings 10. The rotor windings are connected to the star and delta connection ring by rotor winding connection cables (not shown). The jumper windings are connected to the slip rings of the motor (not shown) by jumper winding connection cables 11. Each of the jumper winding connection cables extends over the star and delta connection ring and underneath the reinforcing ring and through the space between each pair of adjacent radial ribs and through the hollow space 12 in the tubular member via radial holes 13 in the tubular member. Each of the jumper connection cables is supported between each pair of radial ribs on a metallic

support rod 14 disposed between and fixed to each pair of radial ribs. The metallic rod is insulated with an insulating material and is preferably mild steel rod. The jumper connection cables are tied to the rods with an insulating material wire or tape 15.
As the jumper winding connection cables are supported and resting on the support rods and held in position by tying with the insulating material wire or tape, they are not loose and sagging in the spaces between pairs of adjacent radial ribs. Therefore, during operation of the motor the jumper winding connection cables do not vibrate and rub against the edges of the star and delta connection ring and reinforcing ring and sidewalls of the radial holes in the tubular member of the shaft. As a result damage to the jumper winding connection cables is prevented. There is no need for periodic replacement of the cables. Running cost of the motor is reduced. Shorting of the cables is avoided and life and reliability of the cables, rotor and motor are increased.
The jumper winding connection cables may be supported in the space between pairs of adjacent radial ribs by support means of different construction and configuration. Instead of being supported on a single support rod, each of the jumper connection cables may be supported on two or more support rods in the space between every pair of adjacent radial ribs. The jumper winding connection cables may extend over the reinforcing ring instead of underneath the reinforcing ring. Such variations in the construction and configuration of the motor of the invention are obvious to a person skilled in the art and are to be construed and understood to be within the scope of the invention.

We Claim:
1. A 3-phase slip ring motor comprising a rotor mounted on a shaft, wherein the shaft comprises a hollow tubular member having a plurality of radial ribs extending from the tubular member in radially spaced apart relationship with one another, a reinforcing ring mounted over the outer ends of the radial ribs and a star and delta connection ring disposed over the reinforcing ring and the rotor comprises a rotor core disposed over and mounted to the star and delta connection ring and having rotor windings and jumper windings, the rotor windings being connected to the star and delta connection ring by rotor winding connection cables and the jumper windings being connected to the slip rings by jumper winding connection cables and wherein each of the jumper winding connection cables extends over the star and delta connection ring and underneath the reinforcing ring and through the space between each pair of adjacent radial ribs and through the hollow space in the tubular member via radial holes in the tubular member and wherein each of the jumper connection cables is supported in the space between each pair of adjacent radial ribs on a support means disposed between and fixed to each pair of adjacent radial ribs.
2. The slip ring motor as claimed in claim 1, wherein the support means comprises at least one metallic rod disposed between and fixed to each pair of radial ribs and insulated with an insulating material and the jumper connection cable is supported on the rod and tied to the rod with an insulating material wire or tape.

3. The slip ring motor as claimed in claim 2, wherein the metallic rod is mild
steel rod,