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 fixture for testing the wound stator of an external rotor motor


APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
Inventors
Kamble Deepak Gajanan and Saple Chandrashekhar Rajaram, both of Crompton Greaves Limited, Speciality Products Centre (SPC), CG Global R&D Center, Kanjurmarg (East), Mumbai 400 042, 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
This invention relates to a fixture for testing the wound stator of an external rotor motor.
The external rotor motor referred to in the specification includes external rotor brushless DC motor or external rotor AC induction motor.
BACKGROUND OF THE INVENTION
An external rotor motor like an external rotor brushless DC motor or an external rotor AC induction motor comprises a wound stator and a rotor disposed over and rotatably held around the stator defining a clearance with the stator. After assembly of the motor if the motor is found to malfunction due to stator faults, the motor will have to be disassembled to locate and rectify the stator faults. Due to stator faults arising from defects like winding errors, the problems that are encountered are, for instance, the motor will not achieve the rated speed or the rotor will not rotate in the desired direction. Disassembling the motor after assembly for the purpose of locating and rectifying stator faults and reassembling the motor is not only cumbersome and difficult to carry out but also time consuming and as a result productivity is also reduced. There is, therefore, need for a fixture for testing the performance of the wound stator of an external rotor motor like an external rotor brushless DC motor or an external rotor AC induction motor prior to assembling the motor so as to avoid problems that will arise from assembling a motor with a faulty stator and disadvantages associated with such problems.
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OBJECTS OF THE INVENTION
An object of the invention is to provide a fixture for testing the performance of the wound stator of an external rotor motor so as to avoid in advance possible malfunctioning of the motor due to stator faults post assembly of the motor and disadvantages arising from stator faults.
Another object of the invention is to provide a fixture for testing the performance of the wound stator of an external rotor motor, which fixture is simple in construction and easy and convenient to operate and is cost effective.
Another object of the invention is to provide a fixture for testing the performance of the wound stator of an external rotor motor, which fixture is flexible and versatile.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a fixture for testing the wound stator of an external rotor motor, which is an external rotor brushless DC motor and the fixture comprises a rotor holder rotatably mounted on a vertical shaft, the upper end of the rotor holder being adapted to hold an equivalent external rotor and the rotor holder having a speed indicator fixed on the outer surface thereof, the lower end of the vertical shaft being mounted on a base and the upper end of the vertical shaft being adapted to locate the wound stator of the motor to be tested, the wound stator being disposed within the equivalent external rotor defining a clearance with the equivalent external rotor, locking means provided at the upper end of the vertical shaft for locking the wound stator in position at the upper end of the vertical shaft and a hall
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sensor holding arm laterally extending from the vertical shaft and having a hall sensor mounted at the distal end thereof facing the rotor.
According to the invention there is also provided a fixture for testing the wound stator of an external rotor motor, which is an external rotor AC induction motor and the fixture comprises a rotor holder rotatably mounted on a vertical shaft, the upper end of the rotor holder being adapted to hold an equivalent external rotor and the rotor holder having a speed indicator fixed on the outer surface thereof, the lower end of the vertical shaft being mounted on a base and the upper end of the vertical shaft being adapted to locate the wound stator of the motor to be tested, the wound stator being disposed within the equivalent external rotor defining a clearance with the equivalent external rotor and locking means provided at the upper end of the vertical shaft for locking the wound stator in position at the upper end of the vertical shaft.
The following is a detailed description of the invention with reference to the accompanying drawings, in which
Fig 1 is an isometric view of the fixture for testing the wound stator of an external rotor brushless DC motor according to an embodiment of the invention;
Figs 2 and 3 are a cross sectional view and an exploded view of the fixture of Fig 1;
Fig 4 is an isometric view of the fixture for testing the wound stator of an external rotor AC induction motor according to an embodiment of the invention; and
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Figs 5 and 6 are a cross sectional view and an exploded view of the fixture of Fig 4.
The fixture 1 for testing the wound stator of an external rotor brushless DC motor as illustrated in Figs 1 to 3 of the accompanying drawings comprises a cupshaped rotor holder 2 having a hub 3 at the centre thereof extending into the cupshaped holder. The cupshaped holder is rotatably mounted on a vertical shaft 4 by a pair of spaced bearings 5, 6 located between the hub and the vertical shaft. 7 is a spacer provided over the vertical shaft between the bearings in order to maintain the spacing between the bearings. 8 is a speed indicator such as a reflector strip fixed on the outer surface of the cupshaped holder. The mouth of the cupshaped holder is provided with a step 9 to removably locate an equivalent external rotor 10 of the motor (not shown) whose wound stator 11 is to be tested. The step at the mouth of the cupshaped holder allows the rotor to be easily located at the mouth of the cupshaped holder and easily removed from the mouth of the cupshaped holder. Therefore equivalent external rotors of different ratings and sizes also can be located at the mouth of the rotor holder. The lower end of the shaft is removably mounted on a base 12 with a screw 13 which is tightened in a screw hole 14 provided in the base and a threaded screw hole 15 provided at the lower end of the vertical shaft, respectively. The head of the screw is accessible through an access hole 16 at the bottom of the base. The screw head is flush with the bottom of the base so that the screw does not create any problem for locating the base on a surface. Because of the flush fit of the screw head at the bottom of the base, the base also looks aesthetically good. 17 is a spacer provided over the vertical shaft between the bottom bearing and the base so as to maintain the spacing between the cupshaped holder and the base. The upper end of the vertical shaft is provided with a step 18 to removably locate the wound stator pack 11 to be tested.
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The wound stator pack is located against the step 18 and disposed within the equivalent external rotor 10 defining a clearance 19 with the rotor. 20 is a key engaged in a keyway 21 formed at the inner diameter of the wound stator and a corresponding keyway 22 formed at the upper end of the vertical shaft so as to hold the wound stator in position and prevent rotational movement of the wound stator about the shaft. 23 is a spacer disposed over the upper end of the vertical shaft and engaged against the wound stator. 24 is a lock nut engaged over the threaded upper end of the vertical shaft in thread engagement therewith. The stator pack is locked in position by tightening the lock nut 24 against the spacer. Because of the use of the spacer 24 wound stators of various sizes can be mounted at the upper end of the vertical shaft by changing the spacer. Therefore, the spacer 24 and step 9 at the mouth of the rotor holder 2 provide flexibility and versatility to the fixture to mount wound stators of varying sizes and to mount equivalent rotors of varying sizes, respectively. 25 is a hall sensor holding arm integrally formed with the spacer 24 and laterally extending from the spacer. 26 is a hall sensor mounted on a hall sensor holder 26 which in turn is mounted at the distal end of the hall sensor holding arm in holes 28 at the distal end of the arm 25. The hall sensor faces the rotor. During testing of the wound stator, the windings of the stator are connected to a power supply through a VAW (Voltage Ampere Wattage) meter (not shown). The VAW meter is also connected to an electronic motor controller (not shown). A speed sensor instrument like tachometer (not shown) is positioned in front of the fixture and is also connected to the electronic motor controller. The hall sensor is also connected to the motor controller. The power supply is switched on and the voltage across the windings and current passing through the windings and current consumed by the windings are input into by the electronic motor controller via the VAW meter. Speed of rotation of the
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cupshaped holder and hence that of the rotor is also input into the motor controller via the tachometer. The hall sensor output pulses are also monitored by the motor controller to determine whether the stator windings are being energised.The sensed values of voltage, current and current consumption and speed of rotation are compared with the rated values stored in the motor controller so as to determine the state and health of the wound stator.
The fixture 29 for testing the performance of the wound stator of an external rotor AC induction motor as illustrated in Figs 4 to 6 of the accompanying drawings comprises an equivalent external rotor 30 located against the step 9 at the mouth of the rotor holder. It does not require the hall sensor, hall sensor holder and the hall sensor holding arm as in the case of the fixture of Figs 1 to 3. During testing of the wound stator, the speed of rotation of the equivalent external rotor and voltage across the windings, current through the windings and current consumed by the windings are sensed by the motor controller through the tachometer and VAW meter and compared with the rated values to determine the sate and health of the wound stator.
According to the invention, the fixture facilitates testing of the performance of the wound stator of an external rotor motor like external rotor brushless DC motor or external rotor AC induction motor to determine in advance the state and health of the wound stator so as to avoid problems that will arise from assembling the motor with a faulty stator and disadvantages associated with such problems. The fixture of the invention is simple in construction and easy and convenient to operate and is cost effective. It is also flezxible to accommodate different sizes of wound stators and equivalent external rotors.
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The equivalent external rotor holder configuration and construction can be different. The equivalent rotor holder can be rotatably mounted on the vertical shaft in a different manner. The lower end of the vertical shaft need not be detachable from the base. It can also be detachably mounted on the base in a different manner. The base can be of a different geometry or configuration. The wound stator can be detachably mounted at the upper end of the vertical shaft in a different manner. The locking means for the wound stator pack can be different. The equivalent external rotor can be detachably mounted at the mouth of the rotor holder in a different manner. The hall sensor holding arm need not be integrally formed with the spacer 23. Such variations of the invention are obvious to those skilled in the art and should be construed and understood to be within the scope of the invention.
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We claim
1) A fixture for testing the wound stator of an external rotor motor, which is an external rotor brushless DC motor and the fixture comprises a rotor holder rotatably mounted on a vertical shaft, the upper end of the rotor holder being adapted to hold an equivalent external rotor and the rotor holder having a speed indicator fixed on the outer surface thereof, the lower end of the vertical shaft being mounted on a base and the upper end of the vertical shaft being adapted to locate the wound stator of the motor to be tested, the wound stator being disposed within the equivalent external rotor defining a clearance with the equivalent external rotor, locking means provided at the upper end of the vertical shaft for locking the wound stator in position at the upper end of the vertical shaft and a hall sensor holding arm laterally extending from the vertical shaft and having a hall sensor mounted at th$ distal end thereof facing the rotor.
2) The fixture as claimed in claim 1, wherein the rotor holder is a cupshaped holder and the mouth of the cupshaped holder is adapted to removably locate the equivalent external rotor.
3) The fixture as claimed in claim 2, wherein the Cupshaped holder comprises a hub at the centre thereof extending into the cupshaped holder and the cupshaped holder is rotatably mounted on the vertical shaft by a piiir of spaced bearings located between the hub and the vertical shaft.
4) The fixture as claimed in anyone of claims 1 to 3, wherein the lower end of the vertical shaft is removably mounted on the base with a screw tightened in a screw
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hole provided in the base and a threaded screw hole provided at the lower end of the vertical shaft with the head of the screw being accessible through an access hole at the bottom of the base, the screw head being flush with the bottom of the base.
5) The fixture as claimed in any one of claims 1 to 4, wherein the upper end of the vertical shaft is provided with a step to removably locate the would stator.
6) The fixture as claimed in any one of claims 1 to 5, wherein the locking means comprises a key engaged in a keyway formed at the inner diameter of the wound stator and a corresponding keyway formed at the upper end of the vertical shaft, a spacer disposed over the upper end of the vertical shaft and engaged against the wound stator and a lock nut engaged over the upper end of the vertical shaft in thread engagement therewith and tightened on the spacer and wherein the hall sensor holding arm is integrally formed with the spacer.
7) The fixture as claimed in any one of claims 1 to 6, wherein the speed indicator is a reflector strip.
8) A fixture for testing the wound stator of an external rotor motor, which is an external rotor AC induction motor and the fixture comprises a rotor holder rotatably mounted on a vertical shaft, the upper end of the rotor holder being adapted to hold an equivalent external rotor and the rotor holder having a speed indicator fixed on the outer surface thereof, the lower end of the vertical shaft being mounted on a base and the upper end of the vertical shaft being adapted to locate the wound stator of the motor to be tested, the wound stator being disposed within the equivalent external
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rotor defining a clearance with the equivalent external rotor and locking means provided at the upper end of the vertical shaft for locking the wound stator in position at the upper end of the vertical shaft.
9) The fixture as claimed in claim 8, wherein the rotor holder is a cupshaped holder and the mouth of the cupshaped holder is adapted to removably locate the equivalent external rotor.
10) The fixture as claimed in claim 9, wherein the cupshaped holder comprises a hub at the centre thereof extending into the cupshaped holder and the cupshaped holder is rotatably mounted on the vertical shaft by a pair of spaced bearings located between the hub and the vertical shaft.
11) The fixture as claimed in anyone of claims 8 to 10, wherein the lower end of the vertical shaft is removably mounted on the base with a screw tightened in a screw hole provided in the base and a threaded screw hole provided at the lower end of the vertical shaft with the head of the screw being accessible through an access hole at the bottom of the base, the screw head being flush with the bottom of the base.
12) The fixture as claimed in any one of claims 8 to 11, wherein the upper end of the vertical shaft is provided with a step to removably locate the would stator.
13) The fixture as claimed in any one of claims 8 to 12, wherein the locking means comprises a key engaged in a keyway formed at the inner diameter of the wound stator and a corresponding keyway formed at the upper end of the vertical
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shaft, a spacer disposed over the upper end of the vertical shaft and engaged against the wound stator and a lock nut engaged over the upper end of the vertical shaft in thread engagement therewith and tightened on the spacer.
14) The fixture as claimed in any one of claims 8 to 13, wherein the speed indicator is a reflector strip.
Dated this 22nd day of December 2008

(Jose M A)
ofKhaitan&Co
Agent for the Applicants
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