ABB FOCH, Hardware Manual, Page: 14 / 38

where
= energy loss in the d u/dt filter E
= 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. C
= average intermediate circuit DC voltage of the drive = approximately 1.35 · U
N
U
dc
= drive supply voltage. U
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
thmax
) and energy dissipation ( E
max
)
values for the d u/dt filters. The filter will not overheat when these values are not
exceeded (and proper cooling is arranged).
E
max
(mJ)
I
thmax
1)
(A)
d u/dt filter type
200 289 FOCH0260-70
280 230
100 289 FOCH0260-72
140 230
260 445 FOCH0320-50
340 361
130 445 FOCH0320-52
170 361
120 720 FOCH0610-70
180 560
260 445
85 880 FOCH0875-70
95 820
115 725
1) In temperatures above +40 °C (+104 °F) and/or altitudes above 1000 m (3281 ft), derate the I
thmax
values as instructed
on page 28 .
￭
Calculation example
An FOCH0610-70 d
u/dt 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
th1
= 105 A.
• 250 m MCMK 3×70+35, C = 0.65 microF/km, I
th2
= 148 A.
• 300 m MCMK 3×120+70, C = 0.8 microF/km, I
th3
= 210 A.
The total capacitance of the motor cables is
C = 0.1 × 0.6 0.25 × 0.65 0.3 × 0.8 microF = 463 nF.
14 Selecting the d u/dt filter