Selection Of The Brake Resistors - Lenze 8400 Hardware Manual

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
Criterion
Continuous braking power
[W]
Heat quantity [Ws]
Resistance []
Active load
Passive load
V [V]
DC
P [W]
max

e

m
t [s]
1
t [s]
cycl
R []
min
EDS84ASC552 EN 10.0
Braking operation with external brake resistor
With active load
≥ P ⋅ η
max
≥ P ⋅ η
max
Can start to move independent of the drive
(e.g. unwinder)
Can stop independent of the drive
(e.g. horizontal travelling drives, centrifuges, fans)
Brake chopper switching threshold from C0174
Maximum occurring braking power determined by the application
Electrical efficiency (controller + motor)
Guide value: 0.54 (0.25 kW) ... 0.85 (11 kW)
Mechanical efficiency (gearbox, machine)
Braking time
Cycle time = time between two successive braking processes (= t
Minimum permissible brake resistance (see rated data of the integrated brake chopper)

Braking operation
Selection of the brake resistors
Application
t
1
⋅ η
⋅
e m
t
zykl
⋅ η ⋅ t
e m
1
2
U
DC
R ≤ R ≤
min
P ⋅ η ⋅ η
max e m
With passive load
t
P ⋅ η ⋅ η
max e m
1
≥ ⋅
t
2
zykl
P
⋅ η ⋅ η
max e m
⋅ t
≥
1
2
+ dead time)
1
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