-----Original Message----- From: RE-wrenches [mailto:[email protected]] On Behalf Of Ray Walters Sent: Sunday, October 12, 2014 16:21 To: RE-wrenches Subject: Re: [RE-wrenches] Quantifying power quality
Hi Dan; I, like Larry, must be amazingly lucky then, because we've solved power quality issues for many years with 50mf caps. Usually, its been front loading washers not running on Trace SW inverters, but also Grundfos CP pumps, too. Never had a problem, and some of these have been running that way for over 15 years. I never had a power quality issue with an Exeltech, so I've never used this trick with your inverters. R.Ray Walters CTO, Solarray, Inc Nabcep Certified PV Installer, Licensed Master Electrician Solar Design Engineer 303 505-8760 On 10/12/2014 12:58 PM, Exeltech wrote: > Wrenches, > > Be careful about connecting *any* capacitors across an inverter's AC output. It's not a smart thing to do. > > While a capacitor may help in some cases when a load has a substantially poor power factor due to significant inductance, there are two serious concerns here: > > 1. The power factor seen by the inverter will be equally bad in the opposite polarity when the inductive load turns off, and IF the capacitor is still connected across the lines. Larry implied the capacitor he connected was disconnected when the load turned off. > > 2. Larry "shot-gunned" a solution. He guessed, and got lucky. We don't know how much actual capacitance was needed in this specific situation. Capacitors connected across an inverter's AC output can destabilize its voltage control loops, leading to erratic AC voltage, resulting in possible damage to the inverter, the load(s) .. or both. > > Power factor is one of the most misunderstood aspects of electricity. > > Dan > (Professional inverter design engineer .. among other things...) > > -------------------------------------------- > On Sun, 10/12/14, Starlight Solar Power Systems <[email protected]> wrote: > > Hi William, > > If you recall a couple years ago we had some discussion here about a problem with a specific make appliance being powered by a Magnum inverter. The problem, it was discovered, was the appliance input PF was creating current demands that the transformer based inverter could not keep up with. When I powered the load with a low cost, high frequency inverter, it worked fine. Apparently the HF inverter can keep up with the current changes faster than the Magnum. > > To fix the problem, a 50mf run type capacitor was installed in the appliance so that it was applied across the AC input when powered on. Everything worked fine then because the cap was taming the wild current created by the low PF. > > Try looking at the current and voltage waveform together (AC shunt, dual trace scope) at the UPS input. If the current is displaying large spikes and/or is out of phase, you may have found the problem is with a non linear load from the UPS. It may be the SI, like the Magnum, can not keep up and so the UPS input circuits are throwing a fit. > > Or, something else you can try, connect a high frequency inverter and try to power the UPS. This can be a portable 12 volt battery and inverter. If the problem disappears, well, you take it from there. > > Larry > Hi William, Power quality, in your case, refers to how close to 60 Hz (frequency component), 120/240 VAC RMS (amplitude component) your voltage waveform is. Every waveform is the superposition of different frequencies, amplitudes etc. Power quality requirements for a devices input or output are usually defined in total harmonic distortion (THD %) and in voltage ranges. THD is an attempt to quantify harmonics on a waveform. It is the ratio of the sum of all harmonics to the fundamental frequency (60Hz in your case). A Sunny Island has THD and amplitude tolerances similar to that of the grid (3%, 105-132VAC). I have found that most generators aren't as close and the distortion in a waveform is easily discernible. My approach to your problem might be to ask for the power quality requirements for the UPS not to beep. Document that the Sunny Islands/Generator system is delivering these requirements during beep events using a power quality analyzer. Put problem back on UPS guy if you can prove that your system is delivering adequate power quality. This is how our utility deals with alleged power quality problems. If the SI system has enough reserve, run it totally off-grid with the grid as backup. Then they will never see any transitions. A Sunny Island that switches to and from grid power probably does not transfer smoothly enough to protect sensitive equipment, but if it is online all the time, using solar to charge the batteries, I would not bother with a UPS. On Sun, Oct 12, 2014 at 11:27 AM, <[email protected]> wrote: perhaps i am not understanding the set-up, but why feed a ups with a ups? doesnt the sunny island already provide ups capabilities for the loads connected to it? todd On Sun, Oct 12, 2014 at 10:40 AM, Tump <[email protected]> wrote: Thats the best fix I've heard yet! Document then DUMP IT! With the power logger you would also be able to capture the transition from utility to SI for your home auto gusto see if he is able to accept the power quality too. On Oct 12, 2014, at 10:24 AM, Chris Mason wrote: I recently worked on a Sunny Island/Sunny Boy system in a nearby island, that powered and protected a complete Home Automation system, including the airco system keeping it cool. I had to restart the Sunny Islands to sort out a COMS problem, which revealed some IT issues. It turns out the Sunny Island system had kept it all running smoothly for about four years without an issue so no-one had realized some of the firmware was crunched. I would get rid of the UPS altogether and that ends the problem. Good luck. On Sun, Oct 12, 2014 at 6:01 AM, Tump <[email protected]> wrote: I have in the past have used the Fluke power logger 1735 , It will monitor 1/3 phases voltages spikes/dips in V, A, Hz , +++ AND one is able to print out a time line of all the "occurrences" that may trip the UPS. I rent this from some folks in Texas quite reasonable ~ $230/month or weekly too. NO MORE finger pointing! I found that when the generator was charging the batteries, the UPS's acceptable voltage window was below the limits and began beeping, due to the poor voltage regulation of the gen under hi load/charging conditions. Are you able to log the Hz as well as the voltages? The ups sometimes have very close voltage windows that they work within. The SI/SB's power quality should NOT be the issue. With this power logger one is able to see a time line and figure out what it operating at the time of "fault/beep" utility power or generator power. Contact me off list for rental contact info or if you would like to see what the graphs look like. Tool is easy to use and VERY informative. On Oct 12, 2014, at 1:21 AM, William Miller wrote: Friends: I am still having a pi$$ing match with the company that installed the expensive home entertainment system for a client over the issue of power quality. The UPS beeps frequently and the AV system crashes now and then. The lead installer has copped an attitude and is blaming the Sunny Island / Sunny Boy / Generac system for the AV system problems. The UPS emails reports in flurries that indicate a "power failure" has occurred. I have a Dataq data acquisition system sampling at a rate that allows me to see the individual cycles on the system output on one of three phases. During the time that a power failure is reported to have occurred each and every cycle looks great. I know this is not a definitive test of power quality so I upped my game. I bought a Fluke VR1710 power monitor and I am recording power quality from the same receptacle that feeds the UPS. I have some log files from the Fluke Power Log software but the instructions are not that great and I don't know how to interpret the data. Do any of you have any experience with this software and could possibly advise me? In a more general sense, how good is power to be called "good"? I have done some research and the industry material is a bit overwhelming. Does anyone have a short answer? And lastly, even though the UPS is beeping, if it is doing what it is designed to do, the power quality should not be an issue because the UPS corrects for any problems. (Actually the UPS was beeping-the best move in this situation was to mute the annunciator so at least the homeowner is not hearing the beeper.) I know others of you are dealing with the same problems because it came up on this forum. I am interested in an approach that verifies the Sunny Islands are producing adequately good power, or not, so I can either address the problem or get the AV guy off my rear end. The system is off grid with: 3 SI6048s in 3 phase 2 SB5000s 1SB4000 1 Generac 40kw generator A Savant home automation system with Furman 1500 UPS. Yes, when the SIs are running into the Furman we have cascading UPSs, but when the generator is powering loads it transfers straight through the SIS and then it is not cascading UPSs. I would hope the Furman could "play nice" with the SIs and maybe it can. If indeed power quality from the SIs is acceptable, maybe we can program the Furman to be more accepting, or just shut off the beeper and email alarms and let it performed its intended function in silence. I will evaluate if alarms are more prevalent during gen run or non-gen run. I will also contact Furman. Thanks in advance. William millersolar.com 805-438-5600 Friends: The system is off grid with: 3 SI6048s in 3 phase 2 SB5000s 1SB4000 1 Generac 40kw generator A Savant home automation system with Furman 1500 UPS. Yes, when the SIs are running into the Furman we have cascading UPSs, but when the generator is powering loads it transfers straight through the SIS and then it is not cascading UPSs. I would hope the Furman could "play nice" with the SIs and maybe it can. If indeed power quality from the SIs is acceptable, maybe we can program the Furman to be more accepting, or just shut off the beeper and email alarms and let it performed its intended function in silence. I will evaluate if alarms are more prevalent during gen run or non-gen run. I will also contact Furman. Thanks for the feedback. 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