Need help selecting an inverter [RE-wrenches]

[Greg Egan]

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Daryl,

I apologize for the misinformation - I didn't realize the x-240 wouldn't 
work with other inverters.

Thanks you for posting your question.

Greg


Christopher Freitas - OutBack Power wrote:

> In order to say if a specific inverter system can run several motors we 
> will need an idea of the start-up current required by each of the 
> motors. If the actual start-up current is not available than the motor 
> size, construction and application can be used to get a fairly accurate 
> idea of what the start amps will be.  
> 
> Based on the ability of the two SW5548s being able to sometimes start 
> the large 7 hp motor,  I would say that a "QUAD" stack (four) of the 
> OutBack FX (sealed) or VFX (vented) series inverters (which version 
> depends upon installation issues and ambient temperatures expected). 
> The FX and VFX versions have the same motor starting ability, but 
> different continuous power ratings (2.5 sealed versus 3.6 kw vented).  
> The VFX has a larger power transformer in addition to the additional 
> airflow - hence the higher power.  
> 
> The X-240 autotransformer will help by keeping the two legs of AC 
> balanced and is also required when more than 2 inverters are connected 
> in the series/parallel configuration.  This trick with the X-240 
> autotransformer is only possible with the OutBack inverters - it will 
> not work with the SW series or other models. 
> 
> With the four OutBack inverters you will have 100 amps RMS / 140 amp 
> peak @ 240 VAC of starting current - this is about 25% more starting 
> current than a pair of SWs.  The X-240 autotransformer will also keep 
> the 120 VAC motors from overloading one pair of inverters when they kick 
> on - the start up current is split up onto all four inverters.  
> 
> The OutBack inverters also do not instantly trip off into overload like 
> the SW series (especially the SW5548s) but instead will supply the motor 
> with reduced AC voltage for up to 5 seconds.  This allows larger motors 
> to be started than one might expect from looking at the motor specs.  
> The AC voltage will however dip during this "soft start" process so the 
> lights will dim etc if they are connected to the same inverter as the 
> large motor.  
> 
> Another option is to look at a separate soft start control for the 
> larger motors.  i have had good luck with the Allen-Bradley STC 
> (starting torque controllers - although they changed the model names a 
> while ago).  The best ones I found were designed to start conveyor belts 
> or similar loads - they have an adjustable ramp time period and current 
> feedback which worked well with the SW series in a couple of my more 
> extreme installations.     
> 
> Christopher Freitas
> OutBack Power Systems, Inc.
> cfreitas at outbackpower.com  www.outbackpower.com
> Tel 360 435 6030  Arlington WA USA
> 
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-- 
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