Xantrex 120 VAC/60 Owner's Manual

Contents

Xantrex 120 VAC/60 Owner's Manual Manual pdf 103 page image

OPERATION 2001 Xantrex Technology, Inc.5916 - 195th Street N. E.Arlington, WA 98223Telephone: 360/435-8826Fax: 360/435-2229www.traceengineering.comSW Series Inverter/ChargerPart No. 2031-5Rev. C: February 2001Page95USING MULTIPLE INVERTERSMultiple SW Series Inverter/Chargers can be used in the same system. There are some limitations to thedesign of the system for successful and reliable operation. For North American applications, the inverterscan be used in a “series” configuration to operate 240 VAC loads and to connect to 120/240 VAC powersystems. Series stacking of “E” versions (230 VAC / 50 Hz) would result in 230/460 VAC power.Two inverters can also be connected together and operated in parallel to provide twice the power at thesame output AC voltage. The inverters can operate in parallel as battery chargers from the same ACsource connected to the same battery. The AC input terminals and DC terminals would then be all inparallel. The inverters will synchronize individually to the AC source and then connect.“SERIES” STACKED OPERATIONAs mentioned, in North America two inverters can be connected in a “series” stacked configuration toprovide 120 and 240 VAC output.When series stacked, you get twice the power of a single inverter available for operating 240 VAC loads,but only one inverter’s power is available for operating a single large 120 VAC load. Separate 120 VACloads can be operated from either inverter. Do not connect the AC output terminals of the inverters inparallel - this will not work. A special stacking interface cable (SWI) is required to connect the seriesstacking ports of the inverter to ensure the output voltage waveforms of the two inverters are phasesynchronized and locked 180 degrees from each other. This allows connection to 120/240 VACgenerators and utility grids. The 120 VAC loads are split and connected to either inverter. Both of theinverters operate completely independently - except their frequency is locked. They do not operate as amaster-slave device as previous inverters have. One inverter can be in battery charger mode while theother is inverting to power an AC load. This independent operation allows many new possible applicationsand abilities that were previously not possible.When inverters are series stacked, they do coordinate all operations that affect 240 VAC loads. Thisrequires that the inverters turn on together and switch to another AC source at the same time. If eitherinverter shuts down, both inverters are inoperable.If no 240 VAC loads are required to be operated, then the need and benefits of stacking are reduced.Stacking adds complexity and will cause both of the inverters to shut down if either inverter goes into anerror condition. With separate (un-stacked) inverters, only one will shut down if over-loaded, etc.When two inverters are connected to a 120/240 VAC distribution system without using the stackinginterface cable, the AC neutral wiring must be capable of handling twice the inverter output. This is due tothe lack of synchronization between the inverters. If both inverters are operating in exact synchronization(as opposed to operating 180 degrees out of synch.), then the AC neutral will carry the current of bothinverters, which was split among the two AC hot conductors. This often is not a problem since the ACdistribution system may be oversized to handle the higher output level of a generator. When an AC sourceis connected to the inverters, the inverters will synchronize independently and transfer at different times.This is not a problem if no 240 VAC loads are connected to the output of the system.WARNING: You must connect the two chassis of the inverters together and to the groundingsystem by their grounding lugs or a hazardous voltage may be present on the chassis of theinverters.INPUT/OUTPUT BYPASS BREAKER SWITCH – 240 VAC LOADSAn inverter “bypass-breaker switch” diverts power around an inverter and is meant to be used only duringtimes of maintenance or to remove the inverter out of the installation. There is a possibility with a multipleinverter installation stacked in “series” (120/240 VAC) with two bypass switches installed, that one inverterbypass breaker switch could be in the Bypass Operation position (power diverted around the inverter’s)and the other inverter bypass breaker switch could be in the Normal Operation position (power passingthru the inverter). The resulting output of the two bypass switches may be less than 240 VAC, which couldcause problems with any 240 VAC loads that are not protected against an AC phase shift.