Lenze 8400 - Manual (Page 253)

Braking operation
Braking operation with external brake resistor
Selection of the brake resistors
8

253 EDS84ASC552 EN 9.1
8.2.4 Selection of the brake resistors
The recommended Lenze brake resistors are adapted to the corresponding controller (with
regard to 150 % of regenerative power). They are suitable for most of the applications.
For special applications, e.g. centrifuges, the brake resistor must meet the following
criteria:
Brake resistor Application
Criterion With active load With passive load
Continuous braking power
[W]
≥ P
max
⋅ η
e
⋅ η
m
⋅
t
1
t
zykl
≥
P
max
⋅ η
e
⋅ η
m
2
⋅
t
1
t
zykl
Heat quantity [Ws] ≥ P
max
⋅ η
e
⋅ η
m
⋅ t
1 ≥
P
max
⋅ η
e
⋅ η
m
2
⋅ t
1
Resistance []
R
min
≤ R ≤
U
DC
2
P
max
⋅ η
e
⋅ η
m
Active load Can start to move independent of the drive
(e.g. unwinder)
Passive load Can stop independent of the drive
(e.g. horizontal travelling drives, centrifuges, fans)
V
DC
[V] Brake chopper switching threshold from C0174
P
max
[W] Maximum occurring braking power determined by the application

e
Electrical efficiency (controller + motor)
Guide value: 0.54 (0.25 kW) ... 0.85 (11 kW)

m
Mechanical efficiency (gearbox, machine)
t
1
[s] Braking time
t
cycl
[s] Cycle time = time between two successive braking processes (= t
1
+ dead time)
R
min
[] Minimum permissible brake resistance (see rated data of the integrated brake chopper)