Lenze EVF9383 - Manual (Page 427)

Braking operation
Brake operation with external brake resistor
Selection of the brake resistors
12
12.1
12.1.1
l
12.1−1 EDSVF9383V EN 7.1−04/2012
12.1 Brake operation with external brake resistor
Larger moments of inertia or longer generator−mode operation require an
external brake resistor. It converts mechanical brake energy into heat.
The brake transistor integrated into the controller switches the external
brake resistor in addition when the DC−bus voltage exceeds a threshold. It
can thus be avoided that the controller sets pulse inhibit in the event of an
"overvoltage" and forces the drive to coast to standstill. External brake
resistors ensure braking operation at any time.
12.1.1 Selection of the brake resistors
The suitable brake resistor must meet the following criteria:
Brake resistor Application
Criteria with active load with passive load
Continuous braking power
[W]
w P
max
@ h
e
@ h
m
@
t
1
t
zykl
w
P
max
@ h
e
@ h
m
2
@
t
1
t
zykl
Thermal capacity [Ws]
w P
max
@ h
e
@ h
m
@ t
1
w
P
max
@ h
e
@ h
m
2
@ t
1
Resistance [ W]
R
min
v R v
U
DC
2
P
max
@ h
e
@ h
m
Field Description
Active load Can move without being influenced by the controller (e.g.
unwinders)
Passive load Decelerates to standstill without influence of the controller
(e.g. horizontal traversing drives, centrifuges, fans)
V
DC
[V] Threshold for brake transistor
P
max
[W] Max. brake power determined by the application
IMPORTANT:
With EVF9381−EV, EVF9382−EV, EVF9383−EV only calculate
with P
max
/2 since these devices dissipate the brake energy
evenly via master and slave. If the brake power is lower, the
brake energy can also be dissipated via the master or the
slave; use P
max
for the calculation.
h
e
Electrical efficiency (controller + motor)
Guide value: 0.94
h
m
Mechanical efficiency (gearbox, machine)
t
1
[s] Braking time
t
cycl
[s] Cycle time = time between two braking processes
(= t1 + break)
R
min
[ W] Lowest permissible brake resistance (see rated data for the
integrated brake transistor)