ABB ACS880-17, Hardware Manual

Page: 76 / 244

76 Guidelines for planning the electrical installation
Additional data for calculating the rise time and the peak line-to-line voltage
If you need to calculate the actual peak voltage and voltage rise time considering the
actual cable length, proceed as follows:
•
Peak line-to line voltage: Read the relative Û
LL
/ U
N
value from the diagram below and
multiply it by the nominal supply voltage ( U
N
).
•
Voltage rise time: Read the relative values Û
LL
/ U
N
and (du/dt)/ U
N
from the diagram
below. Multiply the values by the nominal supply voltage ( U
N
) and substitute into
equation t = 0.8 · Û
LL
/(du/dt).
Selecting the power cables

General rules
Select the input power and motor cables according to local regulations:
•
Select a cable capable of carrying the drive nominal current. See section Ratings
(page 171 ) for the rated currents, and section Typical cable sizes (page 78 ) for typical
cable sizes.
•
Select a cable rated for at least 70 °C maximum permissible temperature of conductor
in continuous use. For US, see
Additional US requirements , page 81 .
•
The inductance and impedance of the PE conductor/cable (grounding wire) must be
rated according to permissible touch voltage appearing under fault conditions (so that
the fault point voltage will not rise excessively when a ground fault occurs).
•
600 V AC cable is accepted for up to 500 V AC. 750 V AC cable is accepted for up to
600 V AC. For 690 V AC rated equipment, the rated voltage between the conductors
of the cable should be at least 1 kV.
Use symmetrical shielded motor cable (see page 80 ). Ground motor cable shields 360° at
both ends. Keep the motor cable and its PE pigtail (twisted shield) as short as possible to
reduce high-frequency electromagnetic emissions.
I Motor cable length
Û
LL
/ U
N
Relative peak line-to-line voltage
(du/dt)/ U
N
Relative du/dt value
Note : Û
LL
and du/dt values are approximately 20% higher with resistor braking.
100 200 300
0.0
0.5
1.0
1.5
2.0
2.5
3.0
l (m)
du/dt
U
N
-------------(1/

s)
Û
LL
/ U
N