18 | SAMLEX AMERICA INC.
WARNING!
If AC GRID input is being fed to the unit through AC Inlet (18, Fig 6.2) and has been switched ON,
it will be bypassed to the AC outlets (17, Fig 6.2) even if the Inverter Section has been switched
OFF either through the 3-Position Rocker Switch (1, Fig 6.1) or through the Wired Remote On/Off
Control (Section 5.7). See explanation below:
As soon as AC GRID input is available, Relays RL-1 and RL-2 will get energized (even if the Inverter Section
has been switched OFF either through the 3-Position Rocker Switch or through the Wired Remote On/Off
Control). Normally Open (NO) contact pairs 1-2 and 3-4 will be closed. As the Inverter section is OFF / not
supplying the load, the Normally Closed (NC) contacts of Relays RL-4 and RL-5 will bypass the AC GRID input
voltage to the AC Outlets (17, Fig 6.2).
5.4.3 Relay for Switching Bond between Output Neutral and Equipment Ground
(Metal Chassis of PSR)
Refer to connections of Relay RL-3 in Fig 5.1.
Relay RL-3 is a Single Pole Double Throw (SPDT) rated at 16A, 250VAC.
When the unit is used as an independent Inverter with no input connection to the AC GRID, it will be
considered as a “Separately Derived System” as per Article 250 of the National Electrical Code (NEC). As
per this Code, the Neutral Conductor of the Inverter output has to be bonded to its Equipment Ground
(metal chassis of the unit). The Equipment Ground (metal chassis of the unit) has to be connected to the
Earth Ground through the Grounding Terminal (16, Fig 6.2) so that in case of a Ground fault, the Inverter
will be able activate its over-current shut down protection. However, if the unit is being used as a UPS
and is fed from AC GRID Supply Panel, it will be considered “NOT Separately Derived System” but as a
“downstream load” as far as the AC GRID Supply Panel is concerned. The AC GRID Supply Panel will have
its Neutral bonded to the Earth Ground (through the Ground Rod). As per NEC, it is not permitted to bond
the Neutral and Equipment Ground (metal chassis) of any down-stream load being fed from the AC GRID
Supply Panel. To meet the above requirements, Relay RL-3 is energized only when the Inverter is supplying
power i.e. when Transfer Relays RL-4 and RL-5 are energized (See Section 5.4.1).
Permanent isolation of Output Neutral from metal Chassis Ground: In certain applications, it may be
necessary to isolate the Output Neutral from the metal chassis ground permanently. For this requirement,
remove the internal Wire Jumper connecting Terminals J2 and J3 (Fig 5.1) [will require removal of top cover
of the unit to access this Wire Jumper].
5.5 OFF-LINE AND ON-LINE MODES OF OPERATION THROUGH PROGRAMMABLE
PARAMETER “INVERTER MODE”
This unit consists of an Inverter and a set of Transfer Relays as described at Section 5.4. It is designed to
function as an Uninterruptible Power Supply (UPS) System where the load will be supplied either by the
external AC GRID input or by the internal Inverter. Option is available through programmable parameter
called “Inverter Mode” to select one of these 2 AC power sources as the Primary Source and the other as
the Backup Source. Programmable options available are as follows:
5.5.1 Off-line Mode: This is the Default Mode.
In this mode, the external AC GRID input is the Primary
Source of power and the Inverter is the Backup Source.
SECTION 5 |
Description & Principles of Operation
