Load Share Overview - Danfoss VLT AQUA Drive FC 202 Design Manual

Product Features

5.11 Load Share Overview

Load share is a feature that allows the connection of DC
circuits of several drives, creating a multiple-drive system
to run 1 mechanical load. Load share provides the
following benefits:
Energy savings
A motor running in regenerative mode can supply drives
that are running in motoring mode.
Reduced need for spare parts
Usually, only 1 brake resistor is needed for the entire drive
system instead of 1 brake resistor per drive.
Power back-up
If there is mains failure, all linked drives can be supplied
through the DC link from a back-up. The application can
continue running or go through a controlled shutdown
process.
Preconditions
The following preconditions must be met before load
sharing is considered:
3x Class L-800 A
380 V
Common mains
disconnect switch
Figure 5.16 Diagram of a Load Share Application Where Best Practices are Applied
Load sharing
Units with the built-in load sharing option contain terminals (+) 89 DC and (–) 88 DC. Within the drive, these terminals
connect to the DC bus in front of the DC-link reactor and bus capacitors.
The load sharing terminals can connect in 2 different configurations.
•
Terminals tie the DC-bus circuits of multiple drives together. This configuration allows a unit that is in a
regenerative mode to share its excess bus voltage with another unit that is running a motor. Load sharing in this
manner can reduce the need for external dynamic brake resistors, while also saving energy. The number of units
MG22B222
Design Guide
2x aR-1000 A
315 kW
91 96
92 97
93 98
82 81
3x 1.2%
Danfoss A/S © 01/2018 All rights reserved.
•
The drive must be equipped with load sharing
terminals.
•
Product series must be the same. Use only VLT
AQUA Drive FC 202 drives with other VLT
Drive FC 202 drives.
•
Drives must be placed physically close to one
another to allow the wiring between them to be
no longer than 25 m (82 ft).
•
Drives must have the same voltage rating.
•
When adding a brake resistor in a load sharing
configuration, all drives must be equipped with a
brake chopper.
•
Fuses must be added to load share terminals.
For a diagram of a load share application in which best
practices are applied, see Figure 5.16. For more information
on load sharing applications, contact Danfoss.
2x aR-1500 A
500 kW
91 96
M
92 97
93 98
82 81
3x 1.2%
3x Class L-1200 A
®
®
AQUA
DC connecting point for
additional drives in the
load sharing application
M
Mains connecting point for
additional drives in the
load sharing application
33
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