78 Chapter 8 Option
NX UPS Single Module And Parallel System 250kVA ~ 800kVA User Manual
No.
Option
Model
Part No.
Remark
16
Four switches assembly (Q1,
Q2, Q3, Q5)
02358887
Installed in factory. Applicable to
500kVA and 600kVA E UPSs
17
Shorting copper bar assembly
when there is no bypass load
sharing inductor
02358889
Installed in factory. Applicable to
500kVA and 600kVA E UPSs
18 LBS
assembly
02350554
8.2 Option
8.2.1 Bypass Load Sharing Inductor
Parallel systems consisting of three or more UPS modules should be fitted with bypass load sharing inductors to
ensure that the static bypass switches, when activated, share the load current. The bypass load sharing inductors
provide droop type current compensation for the otherwise inherent current dispersion due to SCR and cable
impedance differences.
The load sharing imbalance is typically less than 10% of the rated system current depending on the external cable
configuration. Cable lengths from the bypass supply to each UPS module and from the UPS module output to the
paralleling point should be kept as identical as possible.
For 500kVA ~ 600kVA E UPS, this option is installed in factory and it is normally not installed at site.
For 250kVA ~ 400kVA and 600kVA ~ 800kVA UPS, if you buy this option after UPS delivery, please use the following
procedures to install it.
Warning
Only authorized professionals shall install and replace the bypass load sharing inductor.
The cable connection must be made precisely following the instructions. Failure to observe this may result in personnel injury
and cause damage to the UPS and the bypass load sharing inductor.
Installing bypass load sharing inductor of 250kVA ~ 400kVA UPS
1. Installation preparation.
1) Make sure that all installation tools are present, including a cross screwdriver, a pair of diagonal cutting pliers, a
socket spanner and an adjustable spanner.
2) Check that all installation materials are present and complete, including three bypass load sharing inductors, a
cable set (W60, W61, W62), six hexagon head bolts M10 × 40, six sets of M10 flat washers and spring washers, six
M10 hexagon nuts (for fixing the inductor terminals and cables).
2. Installation procedures.
1) Shut down the UPS.
Note
This procedure will cause power interruption to the load.
(1) Turn off the load.
(2) Disconnect the mains input and battery from the UPS.
(3) Open the switch upstream of the UPS bypass input.
(4) Wait five minutes for the internal DC bus capacitors to discharge, until all indicators on the UPS display panel turn off.
2) Remove the side panel and rear panel of the bypass cabinet, disconnect the cables W54, W55 and W56 in the
bypass cabinet from the bypass SCR terminals, and retain the screws.
3) Install the bypass load sharing inductors L1, L2 and L3 in the rear of the bypass cabinet, as shown in Figure 8-1.
The screws and brackets for fixing the bottom of the bypass load sharing inductors are provided in the cabinet.
