Method and apparatus for monitoring the condition of electromechanical systems
A method, apparatus and computer program for monitoring the condition of electromechanical systems in which electrical rotating machinery is used. The method includes measuring current and/or voltage signals, measuring an angular position of a rotating shaft of interest of the electromechanical systems or estimating the value of discrete angular position of a rotating shaft, synchronizing the current and/or voltage signals to the scaled angular displacement of the rotating shaft, dividing the synchronous electrical signals into intervals corresponding to each completed rotation of the rotating shaft, averaging a number of intervals of synchronous electrical signals to obtain an average synchronous electrical signal, extracting characteristic data of the magnitude from the values of the average synchronous electrical signal, and comparing the extracted characteristic data with a threshold limit to alarm the user when the limit is exceeded.
1. A method for monitoring the condition of an electromechanical system comprising the steps of:
measuring current and/or voltage signals of an electromechanical system,
measuring an angular position of a rotating shaft of interest of the electromechanical systems or estimating the value of discrete angular position of a rotating shaft of interest of the electromechanical system,
synchronizing the current and/or voltage signals to the scaled angular displacement of the rotating shaft,
dividing the synchronous electrical signals into intervals corresponding to each completed rotation of the rotating shaft,
averaging a number of intervals of synchronous electrical signals to obtain an average synchronous electrical signal, wherein the averaging of M intervals of synchronous electrical signals corresponding to M complete rotations of the rotation shaft is obtained from the average of the synchronous electrical signals ( Y ), consisting of M averaged values of the electrical signals y n which is calculated from the formula
y
_
n
=
1
M
∑
m
=
1
M
y
m
,
n
,
for
n
=
1
,
2
,
…
,
N
,
where y m,n is the synchronous electrical signal values at sampling point n in interval m, where N is a number of sampling points for every complete rotation of the rotating shaft of the electromechanical system, and where M is a number of averages to be performed,
extracting characteristic data of the magnitude from the values of the average synchronous electrical signal,
comparing the extracted characteristic data of the magnitude with a threshold which is given as a limit, and
indicating an alarm to the user when the limit is exceeded.
2. A method according to claim 1 , wherein a kurtosis S of the average synchronous electrical signals represents the characteristic data of the magnitude from the values of the average synchronous electrical signal and is calculated according to the formula:
S
=
1
N
∑
n
=
1
N
(
y
_
n
-
∑
n
=
1
N
y
_
n
)
2
.
3. An apparatus for monitoring the condition of electromechanical systems comprising:
means for measuring current and/or voltage signals of an electromechanical system,
means for measuring an angular position of a rotating shaft of interest of the electromechanical systems or means for estimating the value of discrete angular position of a rotating shaft of interest of the electromechanical system,
means for synchronizing current and/or voltage signals to a scaled angular displacement of the rotating shaft,
means for dividing the synchronous electrical signals into intervals corresponding to each completed rotation of the rotating shaft,
means for averaging a number of intervals of synchronous electrical signals, wherein the averaging of M intervals of synchronous electrical signals corresponding to M complete rotations of the rotation shaft is obtained from the average of the synchronous electrical signals ( Y ), consisting of M averaged values of the electrical signals y n which is calculated from the formula
y
_
n
=
1
M
∑
m
=
1
M
y
m
,
n
,
for
n
=
1
,
2
,
…
,
N
,
where y m,n is the synchronous electrical signal values at sampling point n in interval m, where N is a number of sampling points for every complete rotation of the rotating shaft of the electromechanical system, and where M is a number of averages to be performed,
means for extracting from the values of the average synchronous electrical signals, a characteristic data of the magnitude, and comparing the extracted characteristic data of the magnitude with a threshold which is given as a limit,
means for comparing the extracted characteristic data of the magnitude with a threshold which is given as a limit, and
means for indicating an alarm to the user when the limit is exceeded.
4. An apparatus according to claim 3 wherein means for synchronizing current and/or voltage signals to a scaled angular displacement of the rotating shaft, means for dividing the synchronous electrical signals into intervals corresponding to each completed rotation of the rotating shaft, means for averaging a number of intervals of synchronous electrical signals, means for extracting from the values of the average synchronous electrical signals, a characteristic data of the magnitude, and comparing the extracted characteristic data of the magnitude with a threshold which is given as a limit are implemented in a synchronous averaging module of a computer device.
5. The apparatus according to claim 4 , wherein a kurtosis S of the average synchronous electrical signals represents the characteristic data of the magnitude from the values of the average synchronous electrical signal and is calculated according to the formula:
S
=
1
N
∑
n
=
1
N
(
y
_
n
-
∑
n
=
1
N
y
_
n
)
2
.
6. A computer program for monitoring the condition of electromechanical systems, which computer program is loadable in and executable on a data processing unit of a computer device and which computer program performs when being executed by the data processing unit of the computer device, wherein the computer program performs a method comprising
measuring current and/or voltage signals of an electromechanical system,
measuring an angular position of a rotating shaft of interest of the electromechanical systems or estimating the value of discrete angular position of a rotating shaft of interest of the electromechanical system,
synchronizing the current and/or voltage signals to the scaled angular displacement of the rotating shaft,
dividing the synchronous electrical signals into intervals corresponding to each completed rotation of the rotating shaft,
averaging a number of intervals of synchronous electrical signals to obtain an average synchronous electrical signal, wherein the averaging of M intervals of synchronous electrical signals corresponding to M complete rotations of the rotation shaft is obtained from the average of the synchronous electrical signals ( Y ), consisting of M averaged values of the electrical signals y n which is calculated from the formula
y
_
n
=
1
M
∑
m
=
1
M
y
m
,
n
,
for
n
=
1
,
2
,
…
,
N
,
where y m,n is the synchronous electrical signal values at sampling point n in interval m where N is a number of sampling points for every complete rotation of the rotating shaft of the electromechanical system, and where M is a number of averages to be performed,
extracting characteristic data of the magnitude from the values of the average synchronous electrical signal,
comparing the extracted characteristic data of the magnitude with a threshold which is given as a limit, and
indicating an alarm to the user when the limit is exceeded.
7. The computer program according to claim 6 , wherein a kurtosis S of the average synchronous electrical signals represents the characteristic data of the magnitude from the values of the average synchronous electrical signal and is calculated according to the formula:
S
=
1
N
∑
n
=
1
N
(
y
_
n
-
∑
n
=
1
N
y
_
n
)
2
.