moog
MSD Servo Drive DC-AC Operation Manual
64
Id.-No.: CA97554-001 Date: 06/2012
•
Maximum current
•
Rated current
A.7.4 Selection of suitable power supply unit
ATTENTION!
!
In all the following dimension calculations always also refer to
the operation manual for the MSD Power Supply Unit
(ID. no.: CA97556-001).
To determine the suitable power supply unit, a power/time graph over a complete ma-
chine cycle must be available for all axes. Figure A.3 presents an example of one.
The power demand of each individual axis at every point in time is added together to
produce the power/time graph for the power supply unit. The following characteristic
values for the power supply unit can be derived from it:
•
Nominal feed power
•
Maximum feed power
•
Nominal feedback power
•
Maximum feedback power
If the simultaneity factor in the axis network is low, it may be possible to select the
largest axis as the AC-AC servo drive and handle the feed for the entire axis network.
Feedback into the supply grid is then not possible however. Regenerative power must be
discharged by way of a braking resistor and converted into heat.
NOTE:
If the supplying voltage grid fails, the power supply unit's design
means it is no longer capable of feedback. For this special emergency case we
therefore recommend you use a braking resistor, with a power rated for this
one braking action.
[ P
1
]
[ P
2
]
[ P
3
]
P
res 1...3
1
0
0
0
0
0
2
3
4
5
6
7
8
9
t [s]
1
0
2
3
4
5
6
7
8
9
t [s]
[ P
res
]
Axis 1
Axis 2
Axis 3
Resultant total power foir supply unit
Fig. A.3 Time/power graph with power supply unit
