In the first installation we experienced this in, a 15 kW Proven turbine was connected to, amongst other load, a 6 kW Windy Boy inverter. This was one of the original 6 kW Windy Boys with the white lid. We noticed however, that as the power rose past 1.3 kW, the inverter would buzz loudly and the lights would flicker significantly. This condition would persist for a second or 2, until power reached about 2 kW, and then stabilised again. The power could drop to below 1 kW again with no problem, but the oscillation would return as it passed 1.3 kW on the way up again. We have not done any more with this one, as the turbine broke down in 2006 and has still not been re-instated. However, that is expected to happen next month, and we will have to deal with the buzzing inverter again....
In the second installation, a 6 kW Proven turbine is connected to a SMC6000A style Windy Boy, the one with the red lid. Soon after commisioning, the customer reported a similar problem in light winds, with the inverter "buzzing", the lights flickering, and also in this in this installation, activation of the mains powered smoke alarm (due to electrical noise rather than smoke!). Neither SMA, nor their UK importer were able to help (although they did propose a number of settings changes to try, the same as with installation 1 above), and the inverter was eventually replaced under warranty. However, this replacement inverter continues to exhibit the same problem, and it it doing the customers nut in, with the fire alarm going off regularly, often in the middle of the night.
The turbine in the second installation broke down recently, and it took a month to get spare parts from Proven. In that time, the fire alarm never went off once, and the lights burned steady, confirming the problem is inverter related.
Recently, we fitted an in line RFI filter in the mains supply to the fire alarm to see if that helps. It hasnt, and we are now having to look at either a power conditioner or even an online UPS in the feed to the smoke alarms. Both are not cheap options, and will only solve the fire alarm problem, not the flickering lights....
Hence the appeal to find out if anyone elese has had this problem with any variant of the SMA inverters, and how it was overcome.
I have again approached SMA and the UK Importer for help, but so far have heard nothing. As I think we drew a blank with both last time round, I'm not too hopeful again this time! In case 2 above, its doing my nut in as much as it is the customers! As an electrical engineer, I cannot see any likely scenario on the grid that could cause this, but would welcome any suggestions!
|SMA Inverter Oscillation||Bryan Rendall - 2008-06-08 17:52:18|
|Re: SMA Inverter Oscillation||Ted Marynicz - 2008-06-09 17:36:50|
I had heard stories that the original SMA 6000 inverters were unreliable but have not got any first hand experience of this.
The fire alarm problem sounds as if the Voltage is dropping below the threshold that the controller is happy with and the alarm is triggered by the on-board battery backup. I have a fire alarm that does exactly this whenever we get a grid outage. The alarm is just behaving as designed.
Is there any measurement and logging of Voltage and Frequency that you can put in place to get a better idea of what is going on?
|Re: SMA Inverter Oscillation||Stuart - 2008-06-09 20:30:35|
I have the white SMA 6000 WindyBoy inverter and so far it has been fine.
|Re: SMA Inverter Oscillation||Bryan Rendall - 2008-06-30 21:57:04|
This isnt so much dropping the voltage but very rapid oscillation of the voltage (flicker). It affects not just the fire alarm, but everything in the house, especially incandescent lighting. I suspect that the fire alarm is triggered not by the low supply voltage, which should not affect it - It should after all run on battery power during a power outage - Instead, I believe its the interconnect on the fire alarms that are picking up what they believe to be an "activate" signal on the interconnect conductor, this signal being spurious noise resulting from the flicker on the mains.
We have already tried to isolate the fire alarms from the mains by fitting a RFI filter on the supply to them. This doesnt seem to have worked. The UK importer of SMA inverters doesnt appear to be interested, and neither are SMA in Germany. The customer is doing his nut, with a fire alarm that goes off frequently, accompanied by wild flickering on the mains. I fear we'll be ripping it all out shortly and putting in another type of turbine / inverter if we cant resolve it soon....
|Re: SMA Inverter Oscillation||Ted Marynicz - 2008-07-01 09:52:26|
do you know what the incoming grid supply characteristics are? i.e. Voltage and Frequency measured on site.
It could be that these are on the boundary of the limits programmed into the inverter.
The power and interconnect cables for fire alarms should be routed away from any other cables.