Sine wave THD for Conext inverters

I'm trying to get some figures for the Total Harmonic Distortion for the Conext SW inverters as I am planning to buy a SW4024 shortly, but have been unable to get Schneider to respond to the question. The datasheet and manuals simply say "pure sine wave". I have played with several inverters including a Phocos 3kVA which stated a nice 5% THD with resistive loads, but demonstrated significant distortion and rapid flickering of lights as soon as I connected even a small SMPS load (a 200 watt Thinkpad laptop power supply!). I have had to throw away lots of money on some of these inverters. So I've been keen to get answers to the following:
(i) (Easy) What is the THD with resistive loads?
(ii) (Subtle) What is the THD when loaded at 50% of capacity with a load that has a crest factor of 3:1?
I suppose the basic electronics architecture being similar, the answers should apply to any of the SWs or XWs.
Anyone measured their Conexts - for (ii) with perhaps an inductive load such as a pump running?
Cheers - Ram
(i) (Easy) What is the THD with resistive loads?
(ii) (Subtle) What is the THD when loaded at 50% of capacity with a load that has a crest factor of 3:1?
I suppose the basic electronics architecture being similar, the answers should apply to any of the SWs or XWs.
Anyone measured their Conexts - for (ii) with perhaps an inductive load such as a pump running?
Cheers - Ram
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Curiously I have emailed Schneider people in 3 countries over the last 3 weeks trying to get a THD figure from them for the Conext SW inverters and there is no answer!
On LED lights I get flicker from the grid on some types but normally only when dimmed. Don't notice anything different on XW4024 when I am drawing form it to cycle the batteries.
Yes I saw it on the XW Spec, not able to see anything in the datasheet or the manual for the SW. Had a chat with an engineer here at Schneider India who seemed to think a THD spec was relevant only for grid-interactive inverters like the XW and not for off-grid inverters like the SW which I believe is wrong.
https://en.wikipedia.org/wiki/Power_inverter
For an induction motor, more or less the energy that is >0% THD is wasted as heat inside the motor. Only the "fundamental frequency" (50 or 60 Hz) is used to rotate the motor. Anything else is wasted as heat in the windings, circulating magnetic currents, etc.
For purely resistive loads (filament bulbs, electric heaters), the THD does not matter--All the energy is "used" (turned into light and heat).
-Bill
Zoneblue " Dave what do you mean by "battery issues". Bad connections or just too small a bank?"
I would say both but it is pretty crazy when someone uses a 200 AH battery with a 4 to 6KW + xw inverter.
400AH has always been speced and for good reason. Less than that is just too small to do any reasonable work and any surges in load will cause electrical issues that may cause lights to flicker or microelectronics stress. We do not like stress!
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-Bill
are for reference and then you write the spec. I would still take an XW over anything else Schneider puts their name on.
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That was long ago so I am glad that you have told me it us that it is well defined now.
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In general, from what I have read is 5% or less THD is "pure sine wave"... And the Conext SW says "pure sine wave" without qualification.
But, as you ask, the voltage wave forms of inverters (and gensets, and even utilities sometimes) can be dramatically affected by their loads. And the quality of the output wave form is quite dependent on the amount of copper and iron that the manufacturer invests in their product.
In the end, spec'ing products is always a game of marketing vs engineering. And since there are few folks out there that has the test gear and can spend the time and money it independently qualify the mfg. claims--We are sort of left with forums like this.
The person posting the question suggests the types of loads they need to run, and hopefully, people with experience running those loads can answer back and say how well their system runs them (or not).
Many designers do test their own and other mfg's equipment--But rarely let those test results out--They cost a lot of time and money to generate. And it is not in their best interest to give that information out for free.
-Bill
I agree engineers do not want to divulge too much data, but THD with linear loads is something that I have seen specced for practically all inverters except Conext SW, and THD with nonlinear loads is something which is not uncommon to spec.
Last but not the least, with due attention paid to Dave's point - THD measured with any HP equipment would be more than useful enough for the purpose :-).
best-Ram
...our product will probably NOT meet your requirements for audio equipment. For the IEC version, the THD is less than 5% with the normal input voltage range 44V-56V. When the input voltage range is 40V-44V, the THD is less than 8%. The tests are conducted under pure resistive load condition. (We are not sure where the
I talked with our compliance team and they provided the following information.
For the CSW (IEC and UL models), the requirements for Vthd on OUTPUT of an inverter are summarized as follows.
IEC 62109-1 = no requirement
EN 50178 = no requirement
IEC 60240-1: (UPS safety) = no requirement
IEC 60240-2: (UPS EMC) = no requirement
IEC 60240-3 (UPS performance) =The effect on the output of the UPS by non-linear loads both in steady-state and dynamic is, in many cases, to cause deviation from the output characteristic specified by the manufacturer/supplier where these are quoted under linear load conditions. Due to the higher peak to r.m.s. steady-state current ratios, the output voltage total harmonic distortion may be increased beyond the manufacturer's stated limit. Compatibility with the load for higher levels of THD is a matter of agreement between the manufacturer and the purchaser.
IEC60335-1 (household equipment) = no requirement
CSA107.1 says 30% THD (mark a warning if higher)
UL1741 says same
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