Xantrex Trace SW4024, Installation Manual

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1.0 INTRODUCTION
4
© 2002 Xantrex Technology Inc.
P/N 975-0041-01-02 Rev A 03/02
STANDARD FEATURES
The Grid Tie Interface (GTI) is an external unit that is required for use with the
Xantrex SW Series Inverters, models SW4024, SW4048, and SW5548 with Rev. 4.2
firmware or higher, being used in Utility Interactive “Sell” mode. This device ensures
compliance with regulatory standards for utility interface applications.
The GTI utilizes a highly-efficient inductor constructed of high temperature
materials and M-6 grade steel laminations, meeting UL Class-H standards.
The unit is housed in a powder-coated, steel enclosure, suitable for indoor
installations and contains dual knockouts for ¾" - 1" and ½" - ¾" conduit
connections. The unit includes a control board with one 10-pin, polarized, connector
that connects to the SW inverter.
The GTI has two functions: 1) Utility Interactive Mode, and 2) Bypass Mode.
Utility Interactive Mode
Utility Interactive Mode is only engaged when the SW inverter begins selling
power in the “Sell” mode. When in this mode, the GTI engages an inductor
through an internal relay that filters out current harmonics and ensures that the
power transferred to the grid has Total Harmonic Distortion (THD) levels that are
within acceptable ranges and ensures the power factor is high. The GTI also
provides anti-islanding protection in the event of a utility grid failure.
Bypass Mode
The GTI includes a bypass relay that is controlled by the current direction and
levels in the GTI and allows the critical loads to be connected to the grid or to the
output of the SW inverter. When a low level “sell” current begins, the GTI will
engage the bypass relay to allow the loads to be connected to the grid. In this
operation (grid-connected), the inverter’s AC1 relay and the bypass relay work
together to ensure fast transfer of the critical loads in a backup situation.
The critical loads are effectively connected directly to the grid – through the GTI
– rather than passing through the inverter, resulting in the “LOAD AMPS AC” menu
item displayed on the SW inverter to read zero. This zero reading will continue until
the inverter batteries require a “buy” current of 10-15 amps AC or if a loss of grid
power is detected. If either one of these conditions is detected, the bypass relay will
engage to allow the critical loads to be directly powered by the inverter (inverter-
connected). The inverter will continue to power the critical loads until another “sell”
current begins, which again switches to the grid-connected operation.
Figure 1-3
Grid Tie Interface Unit