Inrush Current Impulse - REXROTH EcoDrive Cs Project Planning Manual

6-6
Mains and Supply Voltage Connection

Inrush Current Impulse

Computing Inrush Current
Impulse
Numerical example
Reducing inrush current
When the power supply (mains voltage) is switched on, the DC bus
capacitors are first charged via the softstart resistance. This causes a
current impulse when switching on that falls off at increasing DC bus
voltage.
I : inrush current of unit in A
Ein
I : total inrush current in A (value relevant for fusing)
EinGesamt
U : mains input voltage
N1
R : softstart resistance of unit (see relevant technical data)
Softstart
Fig. 6-7: Computing inrush current
Note: To compute the inrush current take all the units connected to
the mains voltage into account.
4 DKC02.3-W0012 drive controllers are connected to a mains connection.
R = 4.7 Ohm (see technical data)
Softstart
U = 264 V (max. allowed mains input voltage)
N1
I = 79.4 A
EIN
total inrush current: I
Note : This inrush current, however, is only of short duration,
because the time constant of the RC element with
T = R x C
Softstart
(T = 2...4 ms)!
For 100 W, 200 W, and 400 W drive controllers: To reduce the inrush
current you can connect our accessories SUP-E05-DKC*CS-SURGEP to
the drive controller at terminal X2 (see chapter 10, page 10-18). This
accessories contains an NTC thermistor (33 Ohm at 25 °C; 19.6 Ohm at
40 °C) to reduce the inrush current.
Risk of damage by heat!
⇒ 400 W drive controllers (DKCxx.x-012) that are
operated with SUP-E05-DKC*CS-SURGEP may
only be operated with a maximum power of 70% .
CAUTION
With higher load the NTC thermistor gets too hot.
Note: For 750 W drive controllers the SUP-E05-DKC*CS-SURGEP
is not suitable.
Rexroth EcoDrive Cs Drives
U * 2
N1
I =
E in
R
Softstart
∑
=
I I
Ein EinGesamt
= 317.6 A
EinGesamt
is within a range of milliseconds
Zwischenkreis
DOK-ECODR3-DKC**.3-CS*-PR02-EN-P