Siemens Simovert Masterdrives Compendium page 924

Engineering Information
Notes regarding the
use of a power back-
up module
Notes on pulse
frequency
11-24
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:
1
2
= ⋅ ⋅ −
W C U (
Link n
2
With a 400 V supply voltage and when C = 5.1 mF and
U = 400 V, for example, the storage capacity is calculated as
Link min
follows:
1
−
3
= ⋅ ⋅ ⋅
W 5 1 10 . (( . 135 400
2
With a 460 V supply voltage, the storage capacity increases to
575 W. The possible bridging time t
power P as follows:
W
=
t
bri
P
The storage capacity during regenerative operation is calculated as
follows:
1
2
= ⋅ ⋅
W C U (
Link max
2
With a 400 V supply voltage and when U
1
−
3
= ⋅ ⋅ ⋅
W 5 1 10 . ( 750
2
During braking, for example, from maximum speed to 0 within time t
the braking energy is calculated as follows:
1
= ⋅ ⋅
W P t
br br max
2
with maximum motor braking power in W
M
Mot v max
=
P
br max
9 55
M Maximum motor torque during braking in Nm
Mot v max
Maximum motor speed during braking in rpm
n
Mot max
♦ 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).
2
U )
Link min
2 2
⋅ − =
) 400 ) 336
is calculated with the output
bri
2
−
U )
Link n
2 2
− − ⋅ =
( 1 35 400 ) )
v
⋅
n
Mot max
⋅ η ⋅ η
Mot Inv
.
6SE7087-6QX70 (Version AE)
Compendium Motion Control
06.2005
Ws
=750 V:
Link max
691 Ws
Siemens AG
SIMOVERT MASTERDRIVES
v