Engineering Information
06.2005
6SE7087-6QX70 (Version AE)
Siemens AG
11-24
Compendium Motion Control
SIMOVERT MASTERDRIVES
The power back-up module is for increasing the capacity of the DC link.
This can bridge a short-time power-system failure, on the one hand,
and also enables intermediate storage of braking energy, on the other.
♦
Storage capacity in the event of a power failure:
W
C U
U
Link n
Link
= ⋅ ⋅
−
1
2
2
2
(
)
min
With a 400 V supply voltage and when C = 5.1 mF and
U
Link min
= 400 V, for example, the storage capacity is calculated as
follows:
W
Ws
= ⋅
⋅
⋅
⋅
−
=
−
1
2
5 1 10
135 400
400
336
3
2
2
.
(( .
)
)
With a 460 V supply voltage, the storage capacity increases to
575 W. The possible bridging time t
bri
is calculated with the output
power P as follows:
t
W
P
bri
=
The storage capacity during regenerative operation is calculated as
follows:
W
C U
U
Link
Link n
= ⋅ ⋅
−
1
2
2
2
(
)
max
With a 400 V supply voltage and when U
Link max
=750 V:
W
Ws
= ⋅
⋅
⋅
− −
⋅
=
−
1
2
5 1 10
750
1 35 400
691
3
2
2
.
(
(
) )
During braking, for example, from maximum speed to 0 within time t
v
the braking energy is calculated as follows:
W
P
t
br
br
v
= ⋅
⋅
1
2
max
with maximum motor braking power in W
P
M
n
br
Mot v
Mot
Mot
Inv
max
max
max
.
=
⋅
⋅
⋅
9 55
η
η
M
Mot v max
Maximum motor torque during braking in Nm
n
Mot max
Maximum motor speed during braking in rpm
♦
Maximum number of power back-up modules which can be
connected on a Compact PLUS unit is
•
Two power back-up modules for rectifier units
•
One power back-up module for converters
The level of the pulse frequency basically affects the dynamic
response. Accordingly, when a high level of dynamic response is
required, the pulse frequency should be set to 10 kHz. Use of the
Compact PLUS does not therefore entail derating. Compact units and
chassis-type units require derating of 6 or 3 Hz and upwards,
depending on their power output (see technical data). A reduction of the
permissible rated current entails a reduction of the permissible
maximum current to the same amount. In addition, the maximum pulse
frequency with chassis-type units is lower than 10 kHz (see technical
data).
Notes regarding the
use of a power back-
up module
Notes on pulse
frequency
