Xantrex Technology 120 VAC/60 owner manual Theory of Operation

OPERATION

OPERATION

The SW Series Inverter/Charger can be configured as a simple stand-alone unit, working in conjunction with your generator to handle loads too large for the generator alone, allowing two-wire or three-wire generators to be turned on and off based on battery voltage or loads amp size, or functioning as a utility interactive inverter which will allow you to send excess power back to the utility grid. Often, the inverter will be set-up to operate in several modes at the same or different times - such as operating as an inverter/charger in utility back-up mode with automatic generator control mode and generator support mode during extended utility outage periods. The extensive configurations available are described in this section will allow you to enhance and customize your inverter’s particular operation.

Before operating the SW Series Inverter/Charger, ensure that the unit is installed in accordance with the instructions in the INSTALLATION section beginning on page 15.

THEORY OF OPERATION

The SW Series inverters employ a new patented inverter design. This design uses a combination of three transformers, each with its own low frequency switcher, coupled in series and driven by separate interconnected micro-controllers. In essence, it is three inverters linked together by their transformers.

Battery

Micro-

Controllers

Low

Frequency

H-Bridge

Low

Frequency

H-Bridge

Low

Frequency

H-Bridge

Bridges are “mixed” by

Micro-Controllers

Controlling the H-Bridges.

Transformer

AC

TransformerLoads

Transformer

Figure 17, Trace™ SW Series Inverter Simple Block Diagram

By mixing the outputs from the different transformers, a sine wave is produced. Shown in Figure 18, is the output waveform from a Trace™ SW Series Inverter/Charger. Notice the “steps” form a staircase that is shaped like a sine wave. The total harmonic distortion in this sine wave approach is typically 3-5%. The multi-stepped output is formed by modulation of the voltage through mixing of the transformers in a specific order. Anywhere from 34-52 “steps” per AC cycle are present in the waveform. The heavier the load or lower DC input voltage the more steps there are in the waveform.

This type of inverter solves many of the problems associated with high frequency or ferroresonant sine wave inverters. The low frequency method described has excellent surge ability, high efficiency (typically 85 to 90%), good voltage and frequency regulation, and low total harmonic distortion.

The inverter runs in two basic formats: as a stand-alone inverter (converting DC to AC), or as a parallel inverter (with its output synchronized to another AC source). In inverter mode, only 60 Hz (50 Hz for export units) waveforms are created. As the battery voltage rises, waveforms with progressively fewer steps are generated. More steps are used when battery voltage decreases. Since the battery voltage tends to drop with increased load, the waveform has increased number of steps with heavier AC loads.

 2001 Xantrex Technology, Inc.	Telephone: 360/435-8826	SW Series Inverter/Charger
5916 - 195th Street N. E.	Fax: 360/435-2229	Part No. 2031-5
Arlington, WA 98223	www.traceengineering.com	Rev. C: February 2001

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