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
An electronic device and a method for sensing the operational status and electrical parameters of an induction motor
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030,
Maharashtra, India, an Indian Company
INVENTORS
MYLAVARAPU Ramamoorty, PASUMARTHI Umamahesh and PARDESHI Suraj Kumar, all of Crompton Greaves Limited, Electronic Development Centre, CG Global R&D, Kanjurmarg (East), Mumbai 400042, Maharashtra, India, all 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 an electronic device and a method for sensing the operational status and electrical parameters of an induction motor.
BACKGROUND OF THE INVENTION
Induction motors are generally used in heavy duty applications like roller mills or air blowers. Sensing of operational status of an induction motor like running condition or stalled, locked or blocked condition and electrical parameters of an induction motor like current drawn, power factor or voltage across the motor is extremely important to ensure healthy operation of the motor and to take timely remedial action and prevent damage to the motor and breakdown of the motor. Operational status of the motor is generally sensed by a sensor unit comprising an intelligent electronic device and ah optical sensor mounted around the motor shaft. The intelligent electronic device comprises a data logger connected to the optical sensor and to a real time controller. The electronic device also comprises a first analog to digital converter connected . to the real time controller and to the stator windings of the motor. The electronic device also comprises a second analog to digital converter connected to the real time controller and to a voltage transformer which is connected to the stator windings of the motor. The real time controller is also connected to a digital display. During operation of the motor, the optical sensor gives a voltage pulse output for every revolution of the motor shaft. The data logger senses the output pulse and gives a proportionate digital signal to the real time controller. The current transformer senses the current drawn by the motor and the respective analog to digital converter converts the current into a proportionate digital signal and outputs the signal to the real time controller. The voltage transformer senses the voltage across the motor and the respective analog

to digital converter converts the voltage into a proportionate analog signal and outputs the signal to the real time controller. Based on the inputs from the data logger and analog to digital converters, the real time controller computes the electrical parameters of the motor and signals the operational status of the motor and drives the display to indicate such parameters and operational status of the motor on a real time basis. In the blocked or stalled condition of the motor, the optical sensor will not give any pulse output and based on this the real time controller senses the locked, blocked or stalled condition of the motor.
A main disadvantage of the above sensor unit is that the optical sensor requires a protective housing and a mounting arrangement for mounting the optical sensor with the housing around the motor shaft. Because of the optical sensor and associated housing and mounting arrangement, the sensor unit is expensive. Besides mounting of the optical sensor with the housing around the motor shaft using the mounting arrangement is quite difficult and cumbersome. Further in case the optical sensor misses any revolution of the motor which does sometimes happen, the display becomes erratic. Therefore, the sensor unit is not very reliable.
OBJECTS OF THE INVENTION
An object of the invention is to provide an electronic device for sensing the operational status
and electrical parameters of an induction motor, which device is simple in construction and
economical.
Another object of the invention is to provide an electronic device for sensing the operational status and electrical parameters of an induction motor, which device is very accurate and reliable.

Another object of the invention is to provide a method for sensing the operational status and electrical parameters of an induction motor, which method is easy and convenient to carry out.
Another object of the invention is to provide a method for sensing the operational status and electrical parameters of an induction motor, which method is very accurate and reliable.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided an electronic device for sensing the operational status and electrical parameters of an induction motor, the device comprising a current transformer and a voltage transformer connected to the stator windings of the motor, a first analog to digital converter connected to the current transformer and to a real time controller, a second analog to digital converter connected to the voltage transformer and to the real time controller, a high precision analog to digital converter connected to the current and voltage transformers and to the real time controller and a digital display connected to the real time controller.
According to the invention there is also provided a method for sensing the operational status and electrical parameters of an induction motor, the method comprising sensing the current drawn by the motor and the voltage across the motor and computing the electrical parameters and operational status of the motor based on the current drawn by the motor and the voltage across the motor and displaying the operational status and electrical parameters of the motor.

The following is a detailed description of the invention with reference to the accompanying drawings, in which the sole Fig 1 is a block diagram of the electronic device according to an embodiment of the invention. The electronic device 1 as illustrated in Fig 1 of the accompanying drawings comprises a current transformer 2 and a voltage transformer 3 connected to the stator windings of the motor 4. A first and second analog to digital converters 5 and 6 are connected to the current transformer and voltage transformer, respectively and a high precision analog to digital converter 7 is connected to the current and voltage transformers. All the analog to digital converters are connected to a real time controller 8 which is connected to a digital display 9. The current transformer senses the current drawn by the motor and the respective analog to digital converter converts the current into a proportionate digital signal and outputs the digital signal to the real time controller. The voltage transformer senses the voltage across the motor and the respective analog to digital converter converts the voltage into a proportionate analog signal and outputs the signal to real time controller. Based on the outputs from the first and second analog to digital converters the real time controller computes the electrical parameters of the induction motor like current drawn, power factor or voltage across the motor and indicate the same on the display. The current and voltage across the motor are collected by the analog to digital converter 7 and based on the outputs from the analog to digital converter 7, the real time controller computes or signals the operational status of the motor like running or blocked, stalled or locked condition of the motor and indicate the same on the display. The invention eliminates the optical sensor and associated protective housing and mounting arrangement. As a result, the cost of the device is reduced and construction of the device is simplified. The computation of operational status of the motor on real time basis is very accurate and therefore

the device is reliable. The method of the invention is also very easy and convenient to carry out ' and accurate and reliable.

We claim :
1) An electronic device for sensing the operational status and electrical parameters of an induction motor, the device comprising a current transformer and a voltage transformer connected to the stator windings of the motor, a first analog to digital converter connected to the current transformer and to a real time controller, a second analog to digital converter connected to the voltage transformer and to the real time controller, a high precision analog to digital converter connected to the current and voltage transformers and to the real time controller and a digital display connected to the real time controller.
2) A method for sensing the operational status and electrical parameters of an induction motor, the method comprising sensing the current drawn by the motor and the voltage across the motor and computing the electrical parameters and operational status of the motor based on the current drawn by the motor and the voltage across the motor and displaying the operational status and electrical parameters of the motor.