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14 Selecting the d u /d t filter
where
= energy loss in the d u /d t filter
E
C
= total capacitance of the motor cable(s), ie, the product of the capacitance/length value
given in the cable catalogue and the length of the motor cable. In case of several motor
cables, the total capacitance is the sum of the individual cable capacitances.
U
= average intermediate circuit DC voltage of the drive = approximately 1.35 · U
dc
U
= drive supply voltage.
N
•
The current flow through the filter is not higher than the maximum allowed value
given in subsection maximum values table below.
Maximum values table
￭
This table gives maximum allowed rms current ( I
values for the d u /d t filters. The filter will not overheat when these values are not
exceeded (and proper cooling is arranged).
d u /d t filter type
FOCH0260-70
FOCH0260-72
FOCH0320-50
FOCH0320-52
FOCH0610-70
FOCH0875-70
1) In temperatures above +40 °C (+104 °F) and/or altitudes above 1000 m (3281 ft), derate the I
on page 28.
Calculation example
￭
An FOCH0610-70 d u /d t filter has been selected for a drive which supplies three motors
with the following cables in parallel:
•
100 m MCMK 3×50+16, C = 0.6 microF/km, I
•
250 m MCMK 3×70+35, C = 0.65 microF/km, I
•
300 m MCMK 3×120+70, C = 0.8 microF/km, I
The total capacitance of the motor cables is
C = 0.1 × 0.6 microF + 0.25 × 0.65 microF + 0.3 × 0.8 microF = 463 nF.
) and energy dissipation ( E
thmax
1)
I
(A)
thmax
289
230
289
230
445
361
445
361
720
560
445
880
820
725
= 105 A.
th1
= 148 A.
th2
= 210 A.
th3
N
)
max
E
(mJ)
max
200
280
100
140
260
340
130
170
120
180
260
85
95
115
values as instructed
thmax
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