Trace PS2512 drop out problems [RE-wrenches]

Christopher Freitas --- OutBack Power cfreitas at outbackpower.com
Tue Dec 16 15:25:18 PST 2003


The issue here, I believe, is how an inverter/charger detects a line 
disturbance that causes the AC to not completely be gone (as when 
throwing a breaker switch) but is 1/3 off - such as the grid dropping to 
80 vac or so... Many "older" inverter/chargers watch the RMS voltage 
(i.e. the average of a whole cycle of AC power) which can make them too 
slow in responding to some situations. Unfortunately, the typical spec 
provided for the UPS/AC transfer time does not include the detection 
time for these situations. 

Real UPS systems (and some brands of newer sinewave inverter/charger 
systems) use much faster methods to detect an AC disturbance - such as 
comparing the actual grid voltage to a syncronized digitized sinewave 
and dropping the grid instantly if a significant difference occurs 
between the real grid and the reference waveform. This allows detection 
of subcycle AC voltage disturbances - with detection AND transfer times 
of 2 milliseconds or less.  

If you could supply the customer with my email address - I would 
consider using this as a good test case for comparing the performance of 
our new 12 volt VFX2812 units.  

Christopher Freitas
OutBack Power Systems, Inc.
cfreitas @ outbackpower.com  
www.outbackpower.com
Arlington WA USA
Tel 360 435 6030  



Richard Perez wrote:
> 
> Hello Wrenches
> 
> Quoted below is a problem that an Home Power reader is having with 
> his Trace PS2512. I am at a loss as to how to help him. Perhaps one 
> of you Wrenches have solved this problem.
> 
> Richard
> Home Power
> 
> At 12:10 -0700 12/16/2003, Jim wrote:
> >We've been fighting with a problem involving a Trace PS2512 
> >inverter. I thought perhaps you might offer some insight into what 
> >is causing the problem and what (if anything) we can do about it.
> >
> >Our Moab, UT office experiences power interruptions lasting anywhere 
> >from under a second to several hours. While relatively infrequent, 
> >they can be quite costly to our programming effort. So, using my 
> >experience at Ray Mesa Power & Light, we built a grid-tied 
> >uninterruptible power supply for our software development 
> >environment. Currently, the system relies entirely on the grid for 
> >charging -- although we anticipate adding solar to it next year.
> >
> >The system (dubbed "MOAB", Mother Of All Backups -- see attached 
> >photo) consists of a Trace PS2512 and about 675 AH in a 12v battery. 
> >It's sourced from a single 30 amp circuit breaker thru the inverter 
> >and back to a secondary breaker panel with two smaller circuits: one 
> >for our server room and one for the programming office. We calculate 
> >the system will carry us for about 8 hours under worst case 
> >conditions. All in all, it works as intended. When we pull the 30 
> >amp breaker, the inverter kicks in with no visible interruption -- 
> >not even a screen flicker. Cut-over is seamless and never fails; 
> >we've never had a computer go down in this situation.
> >
> >On the other hand, we have had several instances in which the office 
> >fluorescent lights barely flicker, the inverter kicks in and 10 out 
> >of 12 computers in the programming office instantly go dead. The two 
> >computers that seem to ride through (both Macs) are always the same 
> >two. Other nearly identical Macs on the same circuit leg as well as 
> >all PC's always go down.
> >
> >We have called Xantrex tech support and although they admit to 
> >having had the problem reported, they are unable to offer either an 
> >explanation or a solution. They claim that there is no firmware 
> >upgrade available (the unit is 18 months old) and don't know what to 
> >suggest. I hinted that maybe they could furnish some means for us to 
> >perform line monitoring to see what was actually triggering the 
> >problem -- they didn't bite. We had already tightened up the grid 
> >voltage limits in the hopes of catching the outage as early as 
> >possible -- no help. Xantrex suggested since tightening the grid 
> >voltage limits doesn't seem to work, maybe we should try widening 
> >the limits. Since there's nothing to lose, we'll probably try it but 
> >I'm hardly optimistic.
> >
> >We have discussed adding small consumer grade UPS's throughout the 
> >office to provide short term ride-through but this defeats the 
> >intent of our original $3000 investment. It just seems illogical to 
> >us that the inverter is able to cut-over without so much as a 
> >flicker when power is cut entirely but can't seem to handle short 
> >blips.
> >
> >Have you heard of this problem? Do you have any idea what causes it 
> >and if so, any suggestions for dealing with it?



Christopher Freitas
OutBack Power Systems, Inc.
cfreitas @ outbackpower.com  
www.outbackpower.com
Arlington WA USA
Tel 360 435 6030  

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