Paralleling two Trace SW inverters [RE-wrenches]

[Michael Welch]

Hello Wrenches. For some reason, "Robert Warren" <robertwarren at mail.com> is unable to post to the list. So, until we figure out what is wrong, I am sending this for him.

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Hi,
 I am new to this list, but not to Homepower folks. I am writing this from merry old England.
 I recently sent in a pair of paralleled SW4548-E inverters for board replacement. The UK authorized Xantrex dealer has replaced both the control board and the AC power board for one inverter, but we are waiting for the other inverter, as his stock of replacement boards has been recently depleted.
 Both  inverter faults were identical: the T-5 transformer on the AC board is blown, which he says is usually caused by high AC voltage.  He has spoken with Trace, and they are doubting they will warranty it, as their repair guy said it highly unlikely that both boards would fail due to internal reasons. I said I would discuss this with Trace myself, and see what they could do for us. 
 The reason they don't have any boards is that he has had to do 3 similar repairs in the past month, so he is out of these boards, and has to order more from the US. This is starting to sound like a generic fault and not one isolated to this installation. 
 From what I have monitored of the one-year old 16-kW Lister generator, the voltage never seems beyond 246 VAC, even on startup, then it drops in to a comfy 238-240. I see the frequency is usually 51.5 Hz until the battery charging load kicks in, then it levels out to 50 Hz. 
 I have it set with the Slave Trace Inverter automatically starting the diesel generator when battery voltage is low for two hours (1.9 VDC/cell). Then, the inverter settiings allows 90 seconds for it to come up to speed and stabilizes its voltage. Ten seconds later the Master inverter charger kicks in, and then both chargers are drawing 18 amps AC max with batteries in low voltage state. 
 I have my own theory about the nature of the failure. This installation has a double pole contactor which I installed between the gen set and battery charger input to the inverter (AC2), mainly so that both chargers shut down at precisely the same moment to avoid the overcurrent we were getting before we added this device. It has worked perfectly for over one year like this. 
 I am thinking that Trace should have a cap filter on the primary side of their parallel transformer to absorb any surge at the moment of disconnect and collaping magnetic field. (It is wired so the two parallel Trace inverter outputs feed the single secondary AC line which goes to the house. The Generator output, has a single output which is split into two leads which feeds the AC2 input.)   
 Has anyone else had a lot of problems with paralleled Trace inverters?
Robert Warren
Senior engineer,
Solar Century 
www.solarcentury.co.uk
   

What will we do if there is another fuel shortage? 
Did you know that there is a pollution free, completely renewable fuel which you can use right now in your own car? 
Don't replace the engine, replace the fuel. Check out my website on making your own fuel: 
http://running_on_alcohol.tripod.com 
robertwarren at mail.com

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