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11.5 Mains Contactor / Fuses
To select suitable mains contactor and fuses for the power connection, a
selection table is available. Note the inrush current of the selected
contactor.
Computing phase current on the mains
To select a suitable mains contactor and fuses for the power connections
it is necessary to rst compute the phase current I
N at the mains.
The mains-side phase current I
N is determined out of the mains
connecting power S
AN
.
Select the mains connecting power in the list or compute it according to
the following formula. With multiple controllers, add the individual powers.
k

60
2
MITTELEFF
ZWD
Ï€
nM
P =
P
ZWD
: required DC bus continuous power in W
M
EFF
: rms torque in Nm
n
MITTEL
: mean speed in min-1
k: factor for motor and controller eciency = 1.25 (MKD, MHD)
Fig. 11-4: Computing DC bus power
FPS 
ZWDN1
=
S N1: connected load in VA
P
ZWD : DC bus continuous power in W
F: connected load factor
F=2.8 for single-phase feed
F for three-phase feed see page 11-9:
"Factor F for Computing the Connected Load"
Fig. 11-5: Computing mains connected load
Single-phase load:
N1
N1
N1
U
S
= I
Three-phase load:
3U
S
= I
N1
N1
N1

IN1: mains-side phase current in A
S
N1: connected load in VA
U
N1: voltage between phases of the mains in V
Fig. 11-6: Computing mains-side phase current
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