15-10 Calculations Rexroth IndraDrive
DOK-INDRV*-SYSTEM*****-PR02-EN-P
15.2 Calculations for Mains Connection
Calculating Mains-Side Phase Current
To select an appropriate mains contactor and the appropriate fusing of
the power connection, the mains-side phase current
IN has to be
calculated before.
The mains-side phase current I
N is determined from the mains connected
load S
LN
.
For max. mains connected load see technical data of the drive controllers
or calculate according to formula below and formulas contained in
appendix. For several drive controllers add the individual mains
connected loads.
k
60
π
2nM
=P
MITTELEFF
DC
⋅
⋅⋅⋅
P
DC
: required DC bus continuous power [W]
M
EFF
: effective torque [Nm]
n
MITTEL
: average speed [min-1]
k: factor for motor and controller efficiency = 1,25 (MKD, MHD)
Fig. 15-25: Calculating the DC bus power
ϕ cos
P
=S
DC
LN
SLN: mains connected load [VA]
P
DC: DC bus continuous power [W]
Fig. 15-26: Calculating the mains connected load
single-phase connection:
N1
N1
N1
U
S
= I
three-phase connection:
3U
S
= I
N1
N1
N1
⋅
IN1: mains-side phase current [A]
S
N1: mains connected load [VA]
U
N1: voltage between phases of mains [V]
Fig. 15-27: Calculating the mains-side phase current
Calculating the Inrush Current
DC(Start)
LN
INE
R
*U
=I
2
∑
=
EIN
EinGesamt
II
IEin: inrush current of respective device [A]
I
EinGesamt: total inrush current in A (relevant value for fusing)
U
LN: mains input voltage
R
DC(Start)
: softstart resistor of the device (see respective technical data)
Fig. 15-28: Calculating the inrush current
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