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CHAPTER 8: FILTER REALIZATION AND EXPERIMENTAL RESULTS
the modulation index, to verify the consistency of the filter behaviour. Three values for
the modulation index have been chosen: the lower one has experimentally been found
in such a way that it will grant the minimum current but still will allow the motor
rotation, the higher value has been set to be equal to 0.85 that is close to the theoretical
maximum value for this type of modulation, plus a middle value chosen between these
two.
8.3.1 Input emissions
This section illustrates that the output filter has no actual influence on the input emis-
sions neither improvement or deterioration for both DM and CM. A first set of figures
show the measured input EMI while supplying the converter with an input supply at
115V, 400Hz. The input emission are compared before and after the filter insertion for
the two output frequencies generated by the converter: 50Hz and 100Hz. Fig. 8.2 and
Fig. 8.3 report the DM emissions while Fig. 8.4 and Fig. 8.5 plot the CM ones.
I [dBµA]
70
60
50
40
30
20
10
0
−10
0.1 1 10
Frequency [MHz]
w/o filter
With filter
Limit
Figure 8.2: Comparison of Measured input DM emissions: without and with output
I [dBµA]
70
60
50
40
30
20
10
0
EMI filter (115V-400Hz to 80V-50Hz)
−10
0.1 1 10
Frequency [MHz]
w/o filter
With filter
Limit
Figure 8.3: Comparison of Measured input DM emissions: without and with output
EMI filter (115V-400Hz to 80V-100Hz)
104