Danfoss Metasys N2 Design Guide

5.6 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 benets:
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 for 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 though a controlled shutdown process.
Preconditions
The following preconditions must be met before load sharing is considered:
•
The drive must be equipped with load sharing terminals.
•
Product series must be the same. Only VLT
®
HVAC Drive drives used with other VLT
®
HVAC Drive 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 conguration, 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 Illustration 5.24.
130BF758.10
380 V
2x aR-1000 A 2x aR-1500 A
3x 1.2%
315 kW 500 kW
3x 1.2%
3x Class L-800 A
3x Class L-1200 A
M
Common mains
disconnect switch
Mains connecting point for
additional drives in the
load sharing application
DC connecting point for
additional drives in the
load sharing application
91
92
93
91
92
93
96
97
98
96
97
98
82 81 82 81
M
Illustration 5.24 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 dierent congurations.
•
Terminals tie the DC-bus circuits of multiple drives together. This conguration 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
Product Features
VLT
®
HVAC Drive FC 102
40 Danfoss A/S © 11/2017 All rights reserved. MG16C302
55

Danfoss Metasys N2 Specifications

General

Brand	Danfoss
Model	Metasys N2
Category	DC Drives
Language	English