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 testing device to check the back emf rating of a magnet ring to be used in a rotor.
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road. Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Deepak Kamble and Anirudha Bharnuke, Crompton Greaves Ltd, Kanjur Marg, Mumbai 400042, Maharashtra, India, both Indian Nationals
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
The present invention relates to a back emf testing device of a magnet ring that goes in to a rotor. This invention is an improvement in, or a modification of the "main invention" described and claimed in 1090/MUM/2010 titled "A testing device for testing performance of a rotor under dynamic conditions".
BACKGROUND OF THE INVENTION
Testing of rotors is a mandatory pre-requisite to rotors prior to their installation with motors. The testing of rotors or magnetic rotors is primarily done so as to determine whether parameters of rotors are in line with the standard parameters (for on-load conditions) or, if any unacceptable deviations have occurred. Deviation from the standard parameters is quite imminent in rotors that are manufactured at one location and transported to a distant location as the standard parameters set during manufacturing may change due to mishandling during transportation.
One of the important parameters in checking of a rotor is the back emf that can be generated by a permanent magnetic ring that is present within the rotor. Even a slight deviation from the standard back emf rated parameter could result in the actual performance of the rotors being greatly hampered. There are few conventional testing devices available currently. however, those do not determine the back emf generated by the rotor during on-load conditions before the rotors are assembled with the motor.

For example, one of the conventional testing devices uses that check rotors uses a probe to check only the flux density of the rotors. There are standard B/H graphs that indicate the proportional back emf generated by the rotor magnet for a measured value of flux density. However such a method of measuring back emf using conventional testing devices tends to be inaccurate. Thus there is a need for a testing device that tests the back emf of the rotors during on-load conditions to determine actual performance of the rotors.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention a testing device for testing the back EMF rating of a magnetic ring to be used in a rotor of a BLDC motor, the device comprising of a base; a pair of upstanding fixed plates mounted to the base and positioned in spaced apart relationship with each other; a rotor housing capable of holding the magnetic ring, the rotor housing mounted to one of the fixed plates for rotation about a horizontal axis and having its inner surface adapted to removably hold the rotor; a BLDC motor mounted linearly adjacent to the rotor housing and capable of rotating the rotor housing along the horizontal axis; a locking means for locking the rotor in the rotor housing; an upstanding slidable plate for mounting a stator and an electronic controller connected to the stator, the slidable plate adapted to describe guided forward and backward linear movement between the fixed plates; and a guiding device, mounted to other of the fixed plates and connected to the slidable plate to linearly move the slidable plate and the stator forward and backward.

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 a perspective view of a testing device showing a stator and a rotor in an open configuration according to an embodiment of the present invention;
FIG. 2 is an exploded view of a testing device of FIG.1
Figure 2 is a perspective view of a testing device showing a stator and a rotor in an closed configuration according to an embodiment of the present invention;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a perspective view of a testing device 100 according to an embodiment of the present invention. The testing device 100 includes a base 102 and a pair of fixed plates, hereinafter referred to as a first fixed plate 104 and a second fixed plate 106, fixedly mounted to the base 102. The base 102 has a length, a width, and a thickness defining the base 102. Both the first fixed plate 104 and the second fixed plate 106 are mounted in upstanding orientation to the base 102. Preferably, both the first fixed plate 104 and the second fixed plate 106 are mounted adjacent to a first end 108 and a second end 110, respectively, of the base 102. The first end 108 and the second end 110 define the length of the base 102.

The first fixed plate 104 has a rotor housing 112 mounted to an inner surface 114 of the first fixed plate 104 and is rotatably engaged therewith. The rotor housing 112 is defined by a generally hollow cylindrical body 116 having an inner surface 118 and an outer surface 120 and rotatable about its horizontal axis with respect to the first fixed plate 104. Preferably, as shown in FIG. 2 that shows an exploded view of the testing device 100, the rotor housing 112 is rotatably engaged to the rotor shaft of a BLDC motor 170 rotor shaft 122 and a pair of bearings having a spacer positioned therebetween. The rotor shaft of the BLDC motor 170 is coupled to the first fixed plate 104 by a screw or by a nut bolt arrangement. The pair of bearings and the spacer allows the rotor housing 112 to be coupled to the rotor shaft of BLDC motor 170.
As shown in FIG. 1, the rotor housing 112 also holds a magnetic ring 130 that is securely mounted to the inner surface 118 of the rotor housing 112. Preferably, the magnetic ring 130 has a plurality of equal opposite (North-South) poles therein. As an outer diameter of the magnetic ring 130 is smaller than inner diameter of the rotor housing 112, the magnetic ring 130 is easily fitted to the rotor housing 112 and securely mounted to the inner surface 118 thereof. In another embodiment of the present invention, a locking nut 132 that removably engages the inner surface 118 of the rotor housing 112 to lock the magnetic ring 130 against the rotor housing 112. Preferably, the inner surface 118 of the rotor housing 112 has a groove 134 formed on the inner surface 118 of the rotor housing 112. Further, the locking nut also has a plurality of cut portions formed on an outer surface of the locking nut 132. Preferably, the groove 134 is circular in shape extending along the inner surface 118 of the rotor housing 112 to accommodate shape of the rotor housing 112, which is generally circular in shape.

Each of the cut portions 136 of the locking nut 132 detachably engages a corresponding groove 134 so as to lock the locking against the rotor housing 112. As the rotor 130 is positioned behind the locking nut 132 within the rotor housing 112, due to this locking of the locking nut 132, the magnetic ring 130 is securely positioned within the rotor housing 112. On removal of the locking nut 132, the magnetic ring 130 is easily removed from the rotor housing 112. In other embodiments of the present invention, other means and mechanisms to lock the magnetic ring 130 against the rotor housing 112 are also envisaged within the scope of the present invention.
As shown in FIG. 1, a slidable plate 138 is slidably disposed between the first fixed plate 104 and the second fixed plate 106. The slidable plate 138 is disposed in upstanding orientation between the first fixed plate 104 and the second fixed plate 106 and is movable therebetween. Further, a guiding device is also mounted in between the first fixed plate 104 and the second fixed plate 106 so as to slidably mount the slidable plate 138 thereon. Preferably, the guiding device includes a pair of guide rods 140 fixedly mounted adjacent to the two upstanding edges, respectively, of the first fixed plate 104 and the second fixed plate 106. As seen from FIGS. 2 and 3, each of the guide rods 140 have a sliding bush 142 slidably adapted thereon. Mounting position of the pair of guide rods 140 is such that the rotor housing 112 is substantially positioned in between the pair of guide rods 140.
Further, as shown in FIGS. 1-3, the slidable plate 138 has a pair of holes 144 formed therein to receive a corresponding guide rod 140 therein. Each of the pair of guide rods 140 is

received within a corresponding pair of holes 144 in such a manner that each of the each of the sliding bushes 142 of the pair of guiding rods is fixedly attached to each of the pair of holes 144. This allows the slidable plate 138 to move over the guide rods 140 thereby allowing the slidable plate 138 to move between the first fixed plate 104 and the second fixed plate 106. Furthermore, the pair of holes 144 is provided adjacent to a bottom edge 146 of the slidable plate 138 so that when the slidable plate 138 is received within the pair of guide rods 140 a small gap is maintained between the base 102 and a bottom edge 146 of the slidable plate 138. This gap ensures that the slidable plate 138 is freely movable on the pair of guide rods 140.
The slidable plate 138 has a stator 148 fixedly mounted thereto. Preferably, the stator 148 is a wound stator that is coupled to the second fixed plate 106 by a stator shaft 150 and a bush 152 (FIGS. 1 and 2). An outer diameter of the stator 148 is smaller than an inner diameter of the rotor 130 so that the stator 148 is received within the rotor housing 112. The testing device 100 is used to test the magnetic ring 130 of a brushless direct current (BLDC) external rotor motor by calculating the amount of back emf that is inducable by the magnetic ring 130. As seen in FIG. 1, an electronic controller, which is preferably a PCB, is also mounted to the slidable plate 138 and positioned on a back side 156 of the stator 148. The electronic controller 154 is electrically connected with the stator 148 to provide necessary electrical power to the stator 148. The electronic controller 154 derives power from an external power source (not shown).

Referring to FIGS. 1-3, an outer surface 158 of the second fixed plate 106 has a cylinder 160 that has a reciprocating shaft 162 therein. As seen in FIG. 2, the second fixed plate 106 has a hole 164 that receives the reciprocating shaft 162. Further, the reciprocating shaft 162 passes completely through the second fixed plate 106 and is connected to a back surface 166 of the slidable plate 138. Preferably, the reciprocating shaft 162 is connected to an adapter 168 that is connected to the back surface 166 of the slidable plate 138. Further, it is also known by virtue of the cylinder operation that the reciprocating shaft 162 is subjected to a forward and a backward stroke. This forward and backward stroke gets transferred in the form of linear motion to the slidable plate 138.
Thus, as the slidable plate 138 is freely movable on the pair of guide rods 140, the slidable pfate 138 linearly moves forward and backward in correspondence with the forward and backward strokes exerted on the reciprocating shaft 162. This allows the reciprocating shaft 162 to describe a guided forward and backward linear motion between the first fixed plate 104 and the second fixed plate 106. Preferably, the cylinder 160 used to perform the guided motion of the slidable plate 138 is a pneumatic cylinder. However, in other embodiments of the present invention, hydraulic cylinders may also be used and be considered within the scope of the present invention.
As shown in FIGS. 1 and 3, when the cylinder 160 exerts a forward stroke on the reciprocating shaft 162, the slidable plate 138 linearly moves forward towards the first fixed plate 104. Due to this linear movement, the stator 148 approaches the rotor housing 112 thereby allowing the stator 148 to be oriented with the magnetic ring 130 in closed

configuration. When the cylinder 160 exerts a full stroke on the reciprocating shaft 162, the slidable plate 138 is further moved linearly towards the rotor housing 112 thereby positioning the stator 148 within the rotor housing 112. The closed configuration of the stator 148 and the rotor 130 is shown in FIGS. 3. On the contrary, when the cylinder 160 exerts a backward stroke, the slidable plate 138 linearly moves backward from the first fixed plate 104 allowing the stator 148 to be linearly moved away from the magnetic ring 130. This allows the stator 148 to be positioned in open configuration with respect to the magnetic ring 130 (See FIG.
!)■
Once the stator 148 and the rotor 130 are in closed configuration with respect to each other, the magnetic ring 130 is rotated within the housing 112. When the BLDC motor 170 is switched in to a working condition and the rotating motion of the shaft is transferred to the rotor housing 112 that is rotatable along the horizontal axis. As the rotor housing 112 rotates, the magnetic ring 112 also rotates around the stator 148.
Due to the rotation of the magnetic ring 130, a certain amount of emf is induced in the stator 148. The emf may vary depending upon the speed with which the motor 170 rotates. For magnetic rings that typically go into rotors, there are well known charts that are available that let designers know the necessary amount of emf (in volts) induced in a stationary winding for variable speeds (in rotations per minute) of magnetic materials.
In order to check the performance of magnetic rings, the BLDC motor 170 can be rotated at different speeds and the emf induced for each of those speeds can be tabulated. The actual

performance of the magnetic 130 is determined by comparing the obtained values with the standard set of values as indicated by the well known charts and calculating the extent of deviation between the two values set. So, by determining the actual performance of the magnetic ring 130. appropriate decision relating to rejecting the magnetic ring 130 is easily taken.
For example, if the magnetic ring 130 does not cause enough induced emf in the stator 148 rotate then during test, then the possibility of the magnetic ring 130 having some abnormality (for eg a hair crack) is very high and as a result the magnetic rings 130 can be immediately rejected. Thus, such magnetic rings 130 being accidently assembled within the rotors is avoided resulting in substantial saving of time, cost, and labor. Another benefit of the various embodiments of the present invention is that the testing machine gives all the performance data without assembling the rotor with the actual motor.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

We Claim:
1. A testing device for testing the back EMF rating of a magnetic ring to be used in a rotor of
a motor, the device comprising:
abase; a pair of upstanding fixed plates mounted to the base and positioned in spaced apart relationship with each other;
a rotor housing capable of holding the magnetic ring, the rotor housing mounted to one of the fixed plates for rotation about a horizontal axis and having its inner surface adapted to removabfy hold the rotor;
a motor mounted linearly adjacent to the rotor housing and capable of rotating the rotor housing along the horizontal axis;
a locking means for locking the rotor in the rotor housing;
an upstanding slidable plate for mounting a stator and an electronic controller connected to the stator, the slidable plate adapted to describe guided forward and backward linear movement between the fixed plates; and
a guiding device mounted to other of the fixed plates and connected to the slidable plate to linearly move the slidable plate and the stator forward and backward.
2. The testing device according to claim 1, wherein the guiding device includes a pair of
guide rods mounted between the pair of fixed plates, the guide rods allowing the slidable
plate to move backward and forward thereon.

3. The testing device according to claim 1, further comprising a cylinder connected to an outer surface of one of the fixed plates, the cylinder having a reciprocating shaft passing through the fixed plate to operably engage the slidable plate for providing guided forward and backward linear movement to the slidable plate.
4. The testing device according to claim 3, wherein the slidable plate linearly moves forward towards one of the fixed plates for positioning the stator within the rotor housing when the reciprocating shaft exerts a forward stroke.
5. The testing device according to claim 4, wherein the stator is disposed within the rotor housing when the reciprocating shaft exerts a forward stroke on the slidable plate to allow the slidable shaft to linearly move forward towards the fixed plate having the rotor housing mounted thereto.
6. The testing device according to claim 5, wherein the stator is disposed in spaced apart relationship with the rotor housing when the reciprocating shaft exerts a backward stroke on the slidable.
7. The testing device according to claim 1, wherein the locking means comprises of a locking nut having a having a plurality of cut portions formed therein, each of the plurality of cut portions removably engaging a corresponding groove formed within the inner surface of the rotor housing.

8. The testing device according to claim I, wherein the rotor housing is rotatably mounted to a rotor housing shaft that rotatably engages one of the fixed plates.