Kollmorgen MMC Smart Drive Series, Hardware Manual

Page: 375 / 386

Kollmorgen - June 2014 373
MMC Smart Drive Hardware Manual
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460V MMC SMART DRIVE DC BUS SHARING
A.3 DC Bus Sharing with AC Power to One Drive
When sharing DC power among several drives with AC power supplying just one of
the drives (
Figure A-2 ), all drives need not be the same size (for example, one drive
may be a MMC-SD-8.0-460, and another drive may be a MMC-SD-1.3-
460). When two or more drives are connected to a shared DC bus in this manner,
there are two limits that must be considered:
• The drives not powered by AC must not consume more power than the “Bus
power available for linking to other drives” as listed in
Table A-1 .
• The total power consumed by all drives cannot exceed the greater of “Bus power
available for linking to other drives” and the kW rating of the AC powered drive as
listed in
Table A-1 .
For example, assume that the AC powered drive is a MMC-SD-24.0-460 and
consumes 14kW, and supplies DC power to two more drives that consume 4kW each
(8kW total). From
Table A-1 , the total DC power available to the non-AC powered
drives is 10kW, meeting the first criteria. The total power consumed is 22kW, and
since the AC powered drive is a 24kW drive, meets the second criteria.
The continuous current available from the drive would be reduced by the same
percentage as the kW. In the example given, the available kW was reduced from 24 to
16kW. Therefore 16/24 = 67%. The drive’s continuous current is reduced by 1/3 from
45 Amps to 30 Amps.
If peak current is to be used at the same time on more than one drive, the total peak
current used by all drives must not exceed that of the main drive. If both the main and
auxiliary drives will accelerate at the same time, the peak current used by auxiliary
drives is subtracted from the available peak current of the main drive. Connection of a
shunt to the main drive is optional depending on the results found in sizing the system.
The system will have the combined DC Bus capacitance of all drives connected.
Table A-2 on page 376 shows the MMC Smart Drive bus capacitance and energy
absorption capability.
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