Method for classifying electrical sheet
View Patent ↗A method for classifying electrical sheet is produced. The electrical sheet is used to produce an electrical machine and is available in the form of a strip roll wherein a magnetic flux that changes over time and that causes a shape change of the strip roll and magnetic losses is produced in the strip roll using an excitation winding fed by a feeding device, the shape change and/or the magnetic losses are measured using a measuring device and the measurement signal obtained is fed to an evaluation device, and the evaluation device categorizes the electrical sheet in regard to noise emission and/or magnetic losses using the measurement signal.
1. A method for classifying electric sheet steel which is used for producing an electrical machine and is in the form of a strip-wound coil, comprising:
producing a magnetic flux that changes over time and that causes a change in the shape of the strip-wound coil and magnetic losses in the strip-wound coil by means of an excitation winding fed by a feeding device;
measuring the change in shape and/or the magnetic losses by means of a measuring device and the measurement signal obtained in the process is supplied to an evaluation device; and
using the measurement signal by the evaluation device to categorize the electric sheet steel with regard to noise emission and/or magnetic losses.
2. The method as claimed in claim 1 , wherein the measuring device comprises a sensor device which is arranged on an end face of the strip-wound coil.
3. The method as claimed in claim 2 , wherein the sensor device is formed by an acceleration sensor.
4. The method as claimed in claim 3 , wherein the acceleration sensor generates a measurement signal which is converted in the evaluation device into a speed signal which is then broken down into frequency components.
5. The method as claimed in claim 4 , wherein a fast Fourier transformation is carried out in the evaluation device.
6. The method as claimed in claim 5 , wherein the excitation winding is fed with a sinusoidal input terminal voltage of predeterminable frequency and of predeterminable amplitude.
7. The method as claimed in claim 6 , wherein the predeterminable frequency is 50 Hz.
8. The method as claimed in claim 6 , wherein the predeterminable frequency 60 Hz.
9. The method as claimed in claim 6 , wherein the magnetic flux is predefined in a technically relevant range between 0.5 T and 2 T steps where T is the unit Tesla.
10. The method as claimed in claim 9 , wherein the magnetic flux is in 0.1 T steps wherein T is the unit Tesla.
11. The method as claimed in claim 10 , wherein only speed amplitudes of the integral multiples of the predefined frequency are used for the categorization of the electric sheet steel.
12. The method as claimed in claim 11 , wherein the speed amplitudes are standardized to a width unit of the strip-wound coil.
13. The method as claimed in claim 12 , wherein the width is 1 m.
14. The method as claimed in claim 12 , wherein a mean value is formed in the evaluation device from spectral speed amplitudes according to a first formula:
V
_
j
=
1
M
∑
i
=
1
M
v
j
,
i
Wherein v i,j are the spectral speed amplitudes,
wherein V j . . . is the mean speed at frequency j,
wherein M . . . is the number of sensors, and
wherein j . . . is the j'th frequency component (e.g. 100 Hz comp.).
15. The method as claimed in claim 14 , wherein for each frequency component of the fast Fourier analysis an averaged sound power level is formed according to a second formula:
L W,j =10· C j ·log( V j ) 2
wherein
C j is an interface factor.
16. The method as claimed in claim 15 , wherein a total sound power level and an A-rated total sound power level are calculated in the evaluation device using a third formula:
L
W
=
10
·
log
(
∑
j
=
1
N
10
0
,
1
*
L
W
,
j
)
wherein N is the number of 50 Hz multiples,
according to a fourth formula:
L
WA
=
10
·
log
(
∑
j
=
1
N
10
0
,
1
*
(
L
W
,
j
-
A
j
)
)
wherein A j is an A-rating at frequency f j .
17. The method as claimed in claim 16 ,
wherein the measuring device comprises a measuring loop which detects the magnetic flux density in the strip-wound coil as a measured value, and,
wherein the measured value is supplied to the evaluation device.
18. The method as claimed in claim 17 , wherein the calculated relative total sound power level and spectral components and measured values of the magnetic flux density are stored in a storage device of the evaluation device.
19. The method as claimed in claim 18 , wherein a loss value is calculated in the evaluation device for one value respectively of a magnetic flux density in the strip-wound coil and is stored in the storage device.