Title of Invention	"AN INTEGRATED DEVICE FOR TEMPERATURE RISE TESTES ON INDUCTION MOTORS BY APPLYING MIXED FREQUENCY"
Abstract	This invention relates to an integrated device for temperature rise tests on induction motors by applying mixed frequency to assess the temperature rise of induction motors on load comprising a main supply of 50 Hz (1) connected to and supplying a main voltage V1 set slightly less than the rated voltage of the motor (3) under test and to an auxiliary variable frequency supply unit (2) which is connected to the motor (3) under test and supplying a field of 40 Hz and auxiliary voltage V2 and an ammeter (A) and voltmeter (V) and two Wattmeters (W1, W2) provided in the line between said auxiliary variable frequency supply (2) and the motor (3) under test characterized in that both the voltages, auxiliary (V2) and the main (V1) are adjusted by simulating the full load conditions in the motor without actually loading the motor by maintaining the following relation V2=(V-V1)x f2 fi Where V is voltage read by the voltmeter (V) and is the rated voltage of motor V1 is the voltage of the main source V2 is the voltage of auxiliary supply f1 is the frequency of main supply and f2 is the frequency of the auxiliary supply, the temperature rise of the motor being carried out through resistance method.

Title of Invention

"AN INTEGRATED DEVICE FOR TEMPERATURE RISE TESTES ON INDUCTION MOTORS BY APPLYING MIXED FREQUENCY"

Abstract

This invention relates to an integrated device for temperature rise tests on induction motors by applying mixed frequency to assess the temperature rise of induction motors on load comprising a main supply of 50 Hz (1) connected to and supplying a main voltage V1 set slightly less than the rated voltage of the motor (3) under test and to an auxiliary variable frequency supply unit (2) which is connected to the motor (3) under test and supplying a field of 40 Hz and auxiliary voltage V2 and an ammeter (A) and voltmeter (V) and two Wattmeters (W1, W2) provided in the line between said auxiliary variable frequency supply (2) and the motor (3) under test characterized in that both the voltages, auxiliary (V2) and the main (V1) are adjusted by simulating the full load conditions in the motor without actually loading the motor by maintaining the following relation V2=(V-V1)x f2 fi Where V is voltage read by the voltmeter (V) and is the rated voltage of motor V1 is the voltage of the main source V2 is the voltage of auxiliary supply f1 is the frequency of main supply and f2 is the frequency of the auxiliary supply, the temperature rise of the motor being carried out through resistance method.

Full Text	This invention relates to an integrated device for temperature rise tests on induction motors by applying mixed frequency to assess the temperature rise of induction motors on load. PRIOR ART At present motors, particularly induction motors are tested by back to back method in a test bed. The present trend is to go for higher unit size of motors rather than more nos of motors coupled together. Load testing of large motors at works is difficult. There are disadvantages associated with the present back to back method of testing of motors. One of the main disadvantages is that it is not possible to load test vertical motors in a vertical position as the loading mechanisms in test bed are of horizontal orientation. Another disadvantages associated with the present system of back to back testing of motors is that quite often two similar machines are not available at a time which delays the test till a second machine is made available, as in the existing system of synchronizing the test for heat run can be performed only with two coupled similar rated motors of the same category. Yet another disadvantage associated with the present system of back to back testing of motors is that a lot of time is consumed in the process of assembly, erection and alignment of two motors as need in case of back to back toad test. Still another disadvantages associated with the present system of back to back testing of motors is that it requires manufacturing time and cost of the test coupling and other coupling accessories for the test. SUMMARY OF THE INVENTION Therefore, the main objection of the present invention is to propose a device for temperature rise tests which is simple and can be performed on single motor i.e. there is no need of an identical second motor as in the case of conventional back to back test. Another object of the present invention is to propose a device for temperature rise tests which is particularly suited for heat run test of vertical motors including squirrel cage and slip-ring types induction motors which is otherwise not possible by conventional method. Yet another object of the present invention is to propose a device for temperature rise test which does not occupy the valuable area of test bed unnecessarily for a longer period because alignment and coupling of other machines are not involved. Still another object of the present invention is to propose a device for temperature rise test which increases the test plant capacity because the actual power needed for testing is much less than the rating of the machine under test. According to the present invention there is provided an integrated device for temperature rise tests on induction motors by applying mixed frequency to assess the temperature rise of induction motors on load replacing the standard method of back-to-back testing of said motors comprising a main supply of 50 Hz connected to an supplying a main voltage V1 set slightly less than the rated voltage of the motor under test and to an auxiliary variable frequency supplying unit which is connected to the motor under test and supplying a filed of 40 Hz and auxiliary voltage V2 and an ammeter (A) and voltmeter (V) and two Wattmeters (W1, W2) provided in the line between said auxiliary variable frequency supply and the motor under test, the voltages, auxiliary (V2) and the main (V1i) are adjusted by simulating the full load conditions in the motor without actually loading the motor by maintaining the relation such as herein described. The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to the non-limiting exemplary embodiments of the invention represented in the accompanying drawings: Figure 1 is a schematic diagram of the device, Figure 2 is a graph showing torque to speed at 40 Hz and 50 Hz source. DETAIL DESCRIPTION OF THE INVENTION According to the invention it is made possible to perform temperature rise test for full load condition in the uncoupled condition provided similar conditions are simulated. These conditions in the motor when it is delivering full load are that it is drawing full load current and consequently full load stator and rotor copper losses, magnetic losses and F & W losses corresponding to full load speed provided it is possible to pass the full load current throuh the stator and rotor and also create the required magnetic losses at rated speed without actually loading the motor then it means that the full load conditions in the motor has been simulated. To explain the background and the concept of the invention we may imagine a situation when two motors of equal rating are mechanically coupled, out of which one is supplied with 50 Hz. source and other with 40 Hz, Motor supplied with 50 Hz sources will try to run at a speed corresponding to 50 Hz while the other with 40 Hz sources will try to run at a speed corresponding to 40 Hz and since both of them are mechanically coupled as the whole system (mechanical) will run at one speed and that will be some intermediate speed between corresponding speeds of 50 Hz and 40 Hz. Therefore, for the motor which is supplied with 50 Hz source, its speed is less than the corresponding synchronous speed, hence it will act as motor while the other one while is supplied with 40 Hz source, its speed being mote than its corresponding synchronous speed will act as generator. It is further explained with respect to the graph of Figure 2. If instead of feeding the differential frequency supplies to different motors mechanically coupled, one motor being fed simultaneously with two different, frequency supplies in series. Assume the system is linear so that superimposition theorem can safely be applied. Firstly the 50 Hz source is short circuited and motor is running on 40 Hz source only, hence it will run at a speed corresponding to 40 Hz. Then 40 Hz. source is short circuited and the motor is running on 50 Hz source only, when it will run at a speed corresponding to 50 Hz. When both of these sources are simultaneously applied then during stating of both fields (40 Hz source field & 50 Hz souce field) are producing motoring torque and motor starts accelerating and as soon as it crosses the speed corresponding to synchronous Speed of 40 Hz field then 40 Hz source starts producing generating torque while that 50 Hz source - still producing motoring torque hence while the net accelerating torque will go on reducing and motor starts running at speed where motoring torque from 50 Hz field is equal to the generating torque from 40 Hz speed as indicated in Fig 1 i.e. on intermediate speed corresponding to 50 Hz & 40 Hz when the motor will draw power from 50 Hz source and will feed it back to 40 Hz source. At this operating point A it indicates that the 40 Hz source is acting as a load on the motor. Test Procedure : a) Connection is made as shown in Figure 1. b) First adjust the excitation of auxiliary variable frequency supply generator (2) such that its terminal voltage is zero. c) Apply the voltage (V1) of main supply say of 50 Hz and adjust the voltage (V1) a bit lesser than the voltage of (V) of motor (3), for example if rated voltage of motor is 3.3 kV then adjust the main supply voltage (V1 ) to around 3.0 kV only. d) As the motor (3) reaches near to its rated speed then increase the excitation of auxiliary generator (2) (say of 40 Hz). As the excitation of auxiliary generator ( 2) is increased the current shown by ammeter (A) will increase. e) Now adjust both the voltages, auxiliary (V~) and main (V1 ) in such a way that the following relation is maintained. V2 = (V - V])x 12 Fl Where V is voltage read by the voltmeter (V)- rated voltage of motor. V1 - voltage of main source. V9 - voltage of auxiliary supply f1 - frequency of main supply f2 - auxiliary supply. The voltage at motor terminal to be maintained equal to the rated voltage of motor. f) Readings shown by ammeter (A), Voltmeter (V) and that by wattmeters (W1, W2) will be on oscillating one. Hence the adjustment to be made as given above should be done in such a way that V being the maximum value read by Voltmeter (V) is rated voltage of motor and the main current shown by ammeter (A) is the rated current of motor. g) Read the wattmeter (W1,W2) readings to give the motor losses. The invention is herein illustrated by an example of the test result as in the following table showing temperature rise of identical motors by the present mixed frequency method and by the existing back to back method. (Table Removed) The test result found above for the present invention is quite comparable with the existing back to back test method. The invention described hereinabove is in relation to a non-limiting embodiment and as defined by the accompanying claims. WE CLAIM; 1. An integrated device for temperature rise tests on induction motors by applying mixed frequency to assess the temperature rise of induction motors on load replacing the standard method of back-to-back testing of said motors comprising a main supply of 50 Hz (1) connected to an supplying a main voltage V1 set slightly less than the rated voltage of the motor (3) under test and to an auxiliary variable frequency supplying unit (2) which is connected to the motor (3) under test and supplying a filed of 40 Hz and auxiliary voltage V2 and an ammeter (A) and voltmeter (V) and two Wattmeters (W1, W2) provided in the line between said auxiliary variable frequency supply (2) and the motor (3) under test, the voltages, auxiliary (V2) and the main (V1) are adjusted by simulating the full load conditions in the motor without actually loading the motor by maintaining the relation such as herein described. 2. An integrated device for temperature rise tests on induction motors by applying mixed frequency substantially as herein described with reference to accompanying drawings.

Full Text

This invention relates to an integrated device for temperature rise tests on induction motors by applying mixed frequency to assess the temperature rise of induction motors on load.
PRIOR ART
At present motors, particularly induction motors are tested by back to back
method in a test bed.
The present trend is to go for higher unit size of motors rather than more nos
of motors coupled together. Load testing of large motors at works is
difficult.
There are disadvantages associated with the present back to back method of testing of motors.
One of the main disadvantages is that it is not possible to load test vertical motors in a vertical position as the loading mechanisms in test bed are of horizontal orientation.
Another disadvantages associated with the present system of back to back testing of motors is that quite often two similar machines are not available at a time which delays the test till a second machine is made available, as in the existing system of synchronizing the test for heat run can be performed only with two coupled similar rated motors of the same category.

Yet another disadvantage associated with the present system of back to back testing of motors is that a lot of time is consumed in the process of assembly, erection and alignment of two motors as need in case of back to back toad
test.
Still another disadvantages associated with the present system of back to back testing of motors is that it requires manufacturing time and cost of the test coupling and other coupling accessories for the test.
SUMMARY OF THE INVENTION
Therefore, the main objection of the present invention is to propose a device for temperature rise tests which is simple and can be performed on single motor i.e. there is no need of an identical second motor as in the case of conventional back to back test.
Another object of the present invention is to propose a device for temperature rise tests which is particularly suited for heat run test of vertical motors including squirrel cage and slip-ring types induction motors which is otherwise not possible by conventional method.
Yet another object of the present invention is to propose a device for temperature rise test which does not occupy the valuable area of test bed unnecessarily for a longer period because alignment and coupling of other machines are not involved.
Still another object of the present invention is to propose a device for temperature rise test which increases the test plant capacity because the actual power needed for testing is much less than the rating of the machine under test.

According to the present invention there is provided an integrated device for temperature rise tests on induction motors by applying mixed frequency to assess the temperature rise of induction motors on load replacing the standard method of back-to-back testing of said motors comprising a main supply of 50 Hz connected to an supplying a main voltage V1 set slightly less than the rated voltage of the motor under test and to an auxiliary variable frequency supplying unit which is connected to the motor under test and supplying a filed of 40 Hz and auxiliary voltage V2 and an ammeter (A) and voltmeter (V) and two Wattmeters (W1, W2) provided in the line between said auxiliary variable frequency supply and the motor under test, the voltages, auxiliary (V2) and the main (V1i) are adjusted by simulating the full load conditions in the motor without actually loading the motor by maintaining the relation such as herein described.

The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to the non-limiting exemplary embodiments of the invention represented in the accompanying drawings:
Figure 1 is a schematic diagram of the device, Figure 2 is a graph showing torque to speed at 40 Hz and 50 Hz source.
DETAIL DESCRIPTION OF THE INVENTION
According to the invention it is made possible to perform temperature rise test for full load condition in the uncoupled condition provided similar conditions are simulated.
These conditions in the motor when it is delivering full load are that it is drawing full load current and consequently full load stator and rotor copper losses, magnetic losses and F & W losses corresponding to full load speed provided it is possible to pass the full load current throuh the stator and rotor and also create the required magnetic losses at rated speed without actually loading the motor then it means that the full load conditions in the motor has been simulated.

To explain the background and the concept of the invention we may imagine a situation when two motors of equal rating are mechanically coupled, out of which one is supplied with 50 Hz. source and other with 40 Hz, Motor supplied with 50 Hz sources will try to run at a speed corresponding to 50 Hz while the other with 40 Hz sources will try to run at a speed corresponding to 40 Hz and since both of them are mechanically coupled as the whole system (mechanical) will run at one speed and that will be some intermediate speed between corresponding speeds of 50 Hz and 40 Hz. Therefore, for the motor which is supplied with 50 Hz source, its speed is less than the corresponding synchronous speed, hence it will act as motor while the other one while is supplied with 40 Hz source, its speed being mote than its corresponding synchronous speed will act as generator.
It is further explained with respect to the graph of Figure 2. If instead of feeding the differential frequency supplies to different motors mechanically coupled, one motor being fed simultaneously with two different, frequency supplies in series. Assume the system is linear so that superimposition theorem can safely be applied. Firstly the 50 Hz source is short circuited and motor is running on 40 Hz source only, hence it will run at a speed corresponding to 40 Hz. Then 40 Hz.

source is short circuited and the motor is running on 50 Hz source only, when it will run at a speed corresponding to 50 Hz. When both of these sources are simultaneously applied then during stating of both fields (40 Hz source field & 50 Hz souce field) are producing motoring torque and motor starts accelerating and as soon as it crosses the speed corresponding to synchronous Speed of 40 Hz field then 40 Hz source starts producing generating torque while that 50 Hz source - still producing motoring torque hence while the net accelerating torque will go on reducing and motor starts running at speed where motoring torque from 50 Hz field is equal to the generating torque from 40 Hz speed as indicated in Fig 1 i.e. on intermediate speed corresponding to 50 Hz & 40 Hz when the motor will draw power from 50 Hz source and will feed it back to 40 Hz source. At this operating point A it indicates that the 40 Hz source is acting as a load on the motor.
Test Procedure : a) Connection is made as shown in Figure 1.

b) First adjust the excitation of auxiliary variable
frequency supply generator (2) such that its terminal
voltage is zero.
c) Apply the voltage (V1) of main supply say of 50 Hz and
adjust the voltage (V1) a bit lesser than the voltage
of (V) of motor (3), for example if rated voltage of motor
is 3.3 kV then adjust the main supply voltage (V1 ) to
around 3.0 kV only.
d) As the motor (3) reaches near to its rated speed then
increase the excitation of auxiliary generator (2)
(say of 40 Hz). As the excitation of auxiliary generator
( 2) is increased the current shown by ammeter (A) will
increase.
e) Now adjust both the voltages, auxiliary (V~) and main
(V1 ) in such a way that the following relation is
maintained.
V2 = (V - V])x 12
Fl Where V is voltage read by the voltmeter (V)- rated voltage
of motor.
V1 - voltage of main source. V9 - voltage of auxiliary supply f1 - frequency of main supply f2 - auxiliary supply.

The voltage at motor terminal to be maintained equal to the rated voltage of motor.
f) Readings shown by ammeter (A), Voltmeter (V) and that by wattmeters (W1, W2) will be on oscillating one. Hence the adjustment to be made as given above should be done in such a way that V being the maximum value read by Voltmeter (V) is rated voltage of motor and the main current shown by ammeter (A) is the rated current of motor.
g) Read the wattmeter (W1,W2) readings to give the motor losses. The invention is herein illustrated by an example of the test result as in the following table showing temperature rise of identical motors by the present mixed frequency method and by the existing back to back method.

(Table Removed)
The test result found above for the present invention is quite comparable with the existing back to back test method.
The invention described hereinabove is in relation to a non-limiting embodiment and as defined by the accompanying claims.

WE CLAIM;
1. An integrated device for temperature rise tests on induction
motors by applying mixed frequency to assess the temperature
rise of induction motors on load replacing the standard method
of back-to-back testing of said motors comprising a main
supply of 50 Hz (1) connected to an supplying a main voltage V1
set slightly less than the rated voltage of the motor (3) under
test and to an auxiliary variable frequency supplying unit (2)
which is connected to the motor (3) under test and supplying a
filed of 40 Hz and auxiliary voltage V2 and an ammeter (A) and
voltmeter (V) and two Wattmeters (W1, W2) provided in the line
between said auxiliary variable frequency supply (2) and the
motor (3) under test, the voltages, auxiliary (V2) and the main
(V1) are adjusted by simulating the full load conditions in the
motor without actually loading the motor by maintaining the
relation such as herein described.
2. An integrated device for temperature rise tests on induction
motors by applying mixed frequency substantially as herein
described with reference to accompanying drawings.

Documents:

937-del-2001-abstract.pdf

937-del-2001-claims.pdf

937-del-2001-correspondence-others.pdf

937-del-2001-correspondence-po.pdf

937-del-2001-description (complete).pdf

937-del-2001-form-1.pdf

937-del-2001-form-19.pdf

937-del-2001-form-2.pdf

937-del-2001-form-3.pdf

937-del-2001-gpa.pdf

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Patent Number

216962

Indian Patent Application Number

937/DEL/2001

PG Journal Number

13/2008

Publication Date

31-Mar-2008

Grant Date

20-Mar-2008

Date of Filing

10-Sep-2001

Name of Patentee

BHARAT HEAVY ELECTRICALS LTD,

Applicant Address

BHEL HOUSE,SIRI FORT,NEW DELHI- 110 049,INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	RAVI PRATAP SINGH	C/O ALL OF BHARAT HEAVY ELECTRICALS LIMITED,(A GOVERNMENT OF INDIA UNDERTAKING),SWITCH GEAR DIVISION,RAMACHANDRA PURAM,HYDERABAD-500 032,INDIA

PCT International Classification Number

G01R 31/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA