ABB ACS880-604LC, Hardware Manual

Page: 25 / 104

50 s of rest). If the actual braking cycle does not correspond to the reference cycle, you
have to calculate the maximum allowed braking power as shown below.
1. Braking energy transferred during any ten minute period must be less than or equal to
the energy transferred during the reference braking cycle:
n P
br
t
br
˜ ˜
P
brmax
100 s
˜ d
where:
Number of braking pulses during a ten minute period n
Maximum allowed braking power (kW) P
br
Braking time (s) t
br
Maximum braking power for a reference cycle (kW) P
brmax
2. The braking power must not exceed the rated maximum value P
brmax
:
P
br
P
brmax
d
Example 1
The duration of braking cycle is 30 minutes. The braking time is 15 minutes.
Result: If the braking time exceeds ten minutes, the braking is considered continuous. The
allowed continuous braking power is 10 percent of the maximum braking power (
P
brmax
).
Example 2
The duration of a braking cycle is three minutes. The braking time is 40 seconds.
1.
„
P
br
<
P
brmax
· 100 s
4 · 40 s
=
0.625 · P
brmax
„
P
brmax
t
P
br
600 s
t
br
T = Duration of braking cycle
2. P
br
< P
brmax
OK.
Result: The maximum allowed braking power for the cycle is 62% of the rated value given
for the reference cycle.
Planning the installation 25