●
be converted into dissipation heat via the braking resistor integrated in
the drive controller or the additional braking resistor
or
●
be stored as energy in the drive controllers and possibly available addi‐
tional capacitors and reused for following acceleration processes. This
reduces the power dissipation generated in the control cabinet and low‐
ers the energy consumption.
The following applies to successful use of additional capacitors to avoid un‐
necessary power dissipation in the control cabinet:
W
R,Anlage
Generated regenerative power of the installation
W
ZW,Geräte
Storable energy of the DC bus capacitors
Fig.15-17:
Condition to Avoid Power Dissipation From the Regenerative Power
Additional Capacitors as Energy
Stores
Many acceleration and deceleration processes are typical for applications
with servo drives (e.g. nibbling machines or roll feeds). This is why it can be
useful for such applications to connect additional capacitors to the DC bus of
the drive controllers. This provides the following advantages:
●
For drive controllers without mains regeneration function, this prevents
the braking resistor in the drive controller from being switched on when
the drives brake. The dissipation heat in the control cabinet is consider‐
ably reduced.
●
The energy stored in the DC bus capacitors can be used for accelera‐
tion. The energy demand of the installation is reduced.
Storable Energy in DC Bus
The specific energy absorption capacity of the drive controllers can be deter‐
mined with the formula below.
W
DC
Storable energy in DC bus
C
DC
DC bus capacitance in device [F]
C
DCext
External DC bus capacitance [F]
U
R_DC On
Braking resistor switch-on threshold
U
DC
DC bus voltage
Fig.15-18:
Storable Energy in DC Bus
The additional capacitor has to be sized in such a way that it can store the
rotary drive energy:
U
R_DC On
Braking resistor switch-on threshold
U
DC
DC bus voltage
W
rot
Rotary energy [Ws]
C
DC
Internal capacitance [F]
C
DCext
Required external DC bus capacitance [F]
Fig.15-19:
Required Additional Capacitance [F]
DOK-INDRV*-SYSTEM*****-PR06-EN-P
Rexroth IndraDrive Drive Systems with HMV01/02 HMS01/02, HMD01, HCS02/03
Bosch Rexroth AG
253/309
Calculations