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
A rotor magnet ring testing device
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Lohokare Yogesh and Virendrakumar S Kori, both of Crompton Greaves Ltd, AMDTC, Global R & D Centre, Bhaskara, Kanjur Marg (East), Mumbai 400 042, India, both Indian Nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a rotor magnet ring testing device. BACKGROUND OF THE INVENTION
A rotor magnet ring of a motor is tested (for magnetization) by generating back emf in a stator of the motor and measuring it. The amount of back emf so generated is the test result. Usually, the back emf is generated by rotating a rotor of the motor by means of an external drive motor coupled mechanically therewith. Such testing of the rotor magnet ring is only possible after the entire motor is assembled. For example, in a BLDC (brushless direct current) fan motor, testing of the rotor magnet ring therein is only possible after assembling the entire BLDC fan motor including the end shields. The external drive motor is coupled mechanically with the rotor end shield for rotating it for generating back emf in the stator. If the back emf so generated is indicative of the rotor magnet ring being faulty (magnetization not as required), it is usually required to be replaced. Replacing the rotor magnet ring involves disassembling and reassembling the entire BLDC fan motor which is tedious, cumbersome and time consuming. It is therefore desirable to test the magnetic ring beforehand without actually installing it into the motor. DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a rotor magnet ring testing device comprising a drive motor vertically disposed and mounted in a support frame at the base thereof, a ring holder dimensioned and profiled to receive and hold a rotor magnet ring to be tested and mounted on the drive motor shaft, a stepper motor mounted at the top of the support frame with the stepper motor shaft depending down coaxially with the drive motor shaft and a wound stator matching with the wound

stator to be used with the rotor magnet ring and dimensioned and profiled to be disposed within the rotor magnet ring located in the ring holder and connected to the stepper motor shaft through a stator raising and lowering means to lower the wound stator into and raise the wound stator from the ring holder.
According to a preferred embodiment, the support frame comprises a base plate having the drive motor mounted thereon, a pair of upright side plates spaced apart from each other and mounted on the base plate and a top plate mounted at the top of the side plates. The ring holder comprises a cup shaped member having a hollow hub depending down from the bottom centre thereof and fitted over the drive motor shaft and rotatably held in a first support plate disposed above the drive motor shaft and mounted to the side plates. The cup-shaped member comprises a step at the inner circumference thereof to locate the rotor magnet ring thereagainst and a retainer ring for retaining the rotor magnet ring in the cup-shaped member in position. The stepper motor is mounted on the top plate with the shaft thereof rotatably held in a second support plate disposed below the top plate and mounted to the side plates. The stator raising and receiving means comprises a sleeve engaged over the stepper motor shaft in thread engagement therewith and having the wound stator shaft fitted to the lower end of the sleeve.
These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig 1 is an isometric view of a rotor magnet ring testing device according to a preferred embodiment.
Fig 2 is an exploded view of a rotor magnet ring testing device according to a preferred embodiment.

Figs 1 and 2 respectively depict an isometric and exploded view of a rotor
magnet ring testing device. According to a preferred embodiment, the rotor magnet
ring is designed to be used in a BLDC fan motor and various components of the
testing device are designed/calibrated accordingly. The testing device comprises a
support frame 1, a drive motor 2, a ring holder 3, a wound stator 4, a stepper motor 5
and a stator raising and lowering means. The support frame comprises a base plate 6,
a pair of upright side plates (7 & 8) spaced apart from each other and mounted on the
base plate 6 and a top plate 9 mounted at the top of the side plates (7 & 8). On the
base plate 6 of the support frame 1 the drive motor 2 is vertically mounted for rotating
the ring holder 3 mounted on a first support plate 10 disposed above a drive motor
shaft 11 of the drive motor 2. According to a preferred embodiment, the ring holder 3
comprises a cup shaped member having a hollow hub 12 depending down from its
center. The hollow hub 12 is fitted on the drive motor shaft 11 and held rotatably
(through bearings 13) on the first support plate 10. The cup-shaped member
comprises a step 14 at its inner circumference for locating the rotor magnet ring 15
thereagainst and a retainer ring 16 for retaining the rotor magnet ring 15 in the cup
shaped member in its position. The cup member or the ring holder 3 in general may
be further adapted to accommodate other components as required in a rotor of an
actual motor in which the rotor magnet ring is to be used. Similarly, the wound stator
4 is provided matching with the wound stator to be used with the rotor magnet ring 15
being tested. The wound stator 4 is adapted to be held within the ring holder 3, raised
therefrom and lowered therein selectively by means of a stepper motor 5 and a stator
raising and lower means. The stepper motor 5 is mounted on the top plate 9 of the
support frame 1 such that its stepper motor shaft 17 is held coaxially with the drive
motor shaft 11 and rotatably (through bearings 18) within a second support plate 19

disposed below the top plate 9 and mounted to the side plates (7 & 8) of the support frame 1. The stator raising and lowering means comprises a sleeve 20, a top end of which is thread engaged over the stepper motor shaft 17 and a lower end connected to a wound stator shaft 21 of the wound stator 4. Upon rotation of the stepper motor shaft 17, the sleeve 20 moves upwards or downwards on account of its thread engagement with the stepper motor shaft 17 thereby raising or lowering the wound stator 4 connected therewith. Lead wires (not shown) from the wound stator are connected to a back emf measuring device (not shown).
For testing the rotor magnet ring 15, it is first placed on the step 14 of the cup-shaped member (or ring holder 3) by a user. The retainer ring 16 is subsequently placed on the edges of the cup-shaped member (or ring holder 3). Thereafter, the stepper motor 5 is rotated to descend (actuate downstream movement of the sleeve 20 over the stepper motor shaft 17 in thread engagement therewith) the wound stator into the cavity of the cup-shaped within the rotor magnet ring 15 upto a pre-determined position and held in such position. The drive motor 2 is then actuated to rotate the ring holder 3 at a pre-determined speed. While the ring holder 3 is being rotated, back emf is induced within the wound stator 4 which is measured by the back emf measuring device connected to the lead wires of the wound stator 4. Thereafter, the drive motor 2 is signalled off and the stepper motor 5 is signalled to ascend (actuate upstream movement of the sleeve 20 over the stepper motor shaft 17 in thread engagement therewith) the wound stator 4 at a pre-determined position. The retainer ring 16 and the rotor magnet ring 15 is subsequently removed from the ring holder 3 by the user. The above process is repeated for a different rotor magnet ring (of the same lot).
According to the invention, the testing device facilitates a quick, easy and hassle free testing of the rotor magnet ring without having to actually install it in the

actual motor in which it is to be used. Thus a lot of production time and resources are saved in removing and replacing the rotor magnetic ring should the rotor magnet ring be detected faulty.
It will be apparent to a person skilled in the art that the shape of the ring holder, profile therein for receiving and holding the rotor magnet ring and other design parameters may vary according to the design parameters of the actual rotor in which the rotor magnet ring is to be held. Similar limitation will also apply to the wound stator.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the scope of the invention as defined in the appended claims.

I/We claim:
1. A rotor magnet ring testing device comprising a drive motor vertically disposed and mounted in a support frame at the base thereof, a ring holder dimensioned and profiled to receive and hold a rotor magnet ring to be tested and mounted on the drive motor shaft, a stepper motor mounted at the top of the support frame with the stepper motor shaft depending down coaxially with the drive motor shaft and a wound stator matching with the wound stator to be used with the rotor magnet ring and dimensioned and profiled to be disposed within the rotor magnet ring located in the ring holder and connected to the stepper motor shaft through a stator raising and lowering means to lower the wound stator into and raise the wound stator from the ring holder.
2. The testing device as claimed in claim 1, wherein the support frame comprises a base plate having the drive motor mounted thereon, a pair of upright side plates spaced apart from each other and mounted on the base plate and a top plate mounted at the top of the side plates.
3. The testing device as claimed in claim 1 or 2, wherein the ring holder comprises a cup shaped member having a hollow hub depending down from the bottom centre thereof and fitted over the drive motor shaft and rotatably held in a first support plate disposed above the drive motor shaft and mounted to the side plates.
4. The testing device as claimed in claim 3, wherein the cup-shaped member comprises a step at the inner circumference thereof to locate the rotor magnet ring thereagainst and a retainer ring for retaining the rotor magnet ring in the cup-shaped member in position.

5. The testing device as claimed in anyone of claims 1 to 4, wherein the stepper motor is mounted on the top plate with the shaft thereof rotatably held in a second support plate disposed below the top plate and mounted to the side plates.
6. The testing device as claimed in anyone of claims 1 to 5, wherein the stator raising and receiving means comprises a sleeve engaged over the stepper motor shaft in thread engagement therewith and having the wound stator shaft fitted to the lower end of the sleeve.