Voltage Stabilizer, UPS, battery backup recommendations please?

[kartechnology]

I am using NKB 5kva for approx 1.5 years. No issues so fa

Transformer in itself is a major factor in such equipments. Apart from winding material (aluminium or copper) , it's insulation, wire thickness, purity, core material and lamination grade etc decide the cost , performance and efficiency.

Like all the members here, I am also using NKB 5 KVA system from more than a year now. Never ever faced any issues. The system came in a solid wooden crate and was extremely easy to install by following the user manual.
Voltage here fluctuates anywhere from 180 to 250 but the system has always given constant output without even a trace of flicker and is dead silent....
They clearly have installations and service support all across the country. Even saw some excellent reviews from their overseas clients.

Numax system having major performance issues right away rightly raises questions on material quality IMO. It clearly wasn't built and tested properly before delivery.

Generally speaking, I don't think any company would be able to tag and sell their product at a higher price if their quality doesn't have substance. Sayan is right, NKB must have reasons behind their pricing.

in general one cant notice the voltage fluctuations unless
1. wifi cloud data logging is present in stabilizer - and the sync rate needs to be like every second(which i have) unlike their standard server which updates every 30 seconds.
2. monitoring the output voltage with some other device, eg. wifi connected solar inverter/ sonoff pow, etc to see any spikes/sags
3. actual output tested with a oscilloscope - best one
4. observing the tubelights / bulbs for slight flicker

there are times when the PWM is going off and restarting as per the device logs. in that time the output =input voltage. could be a DSP hangup. tech has told me many newer units are facing this voltage fluctuating issue. and yes, pasting a QC OK sticker on the cabinet isnt enough. one of the bolts on the heatsink for the wires were loose when the unit came. so ... i think numax is not the one even though cost is less...previously igbts used to fail itseems..now they replaced that with better ones and facing this voltage issue.

Currently Fuji Electric P2hf 40G120HD 31330 IGBTs are used in my unit.

tublights flicker corresponding to this..fan noise from solar inverter..the vibrating/buzzing from transformer

@funnyprogrammer what to do now..waiting for a new / replacement motherboard currently...suggest you to check the output instead of relying on the front display

 

[Musicforsalvation]

in general one cant notice the voltage fluctuations unless
1. wifi cloud data logging is present in stabilizer - and the sync rate needs to be like every second(which i have) unlike their standard server which updates every 30 seconds.
2. monitoring the output voltage with some other device, eg. wifi connected solar inverter/ sonoff pow, etc to see any spikes/sags
3. actual output tested with a oscilloscope - best one
4. observing the tubelights / bulbs for slight flicker

there are times when the PWM is going off and restarting as per the device logs. in that time the output =input voltage. could be a DSP hangup. tech has told me many newer units are facing this voltage fluctuating issue. and yes, pasting a QC OK sticker on the cabinet isnt enough. one of the bolts on the heatsink for the wires were loose when the unit came. so ... i think numax is not the one even though cost is less...previously igbts used to fail itseems..now they replaced that with better ones and facing this voltage issue.

Currently Fuji Electric P2hf 40G120HD 31330 IGBTs are used in my unit.

tublights flicker corresponding to this..fan noise from solar inverter..the vibrating/buzzing from transformer

@funnyprogrammer what to do now..waiting for a new / replacement motherboard currently...suggest you to check the output instead of relying on the front display

I have used multimeter on various occasions to monitor the input and output voltage and also have never seen any flicker in LED lights.

I was provided a detailed test report of the system before it was shipped.

Certainly a QC ok sticker makes no sense as it clearly wasn't tested before delivery. Loose bolts, buzzing transformer shows poor workmanship and negligence and also raises many credibility questions.

You are correct, numax is not the one which can be relied upon. I had received some similar feedback for them when I was searching for a good supplier.

 

[kartechnology]

I have used multimeter on various occasions to monitor the input and output voltage and also have never seen any flicker in LED lights.

I was provided a detailed test report of the system before it was shipped.

Certainly a QC ok sticker makes no sense as it clearly wasn't tested before delivery. Loose bolts, buzzing transformer shows poor workmanship and negligence and also raises many credibility questions.

You are correct, numax is not the one which can be relied upon. I had received some similar feedback for them when I was searching for a good supplier.

so they sent a refurb board. but seems like the dsp chip which can be swapped out is the culprit.
I will see till evening and swap out the new board with the refurb dsp and see.

can anything be done for this? i have spent 40k on this bad company...even troubleshooting they are unable to do properly. since i've worked with the parent r&d team i have some idea where things are going wrong... have a lemon makes me feel bad. i would be happy to get a refund.

PS: the dsp chip which was tied to the motherboard with a zip tag itself was loose and dsp was also not seated fully.. great QC..

 

[jsmithe]

in general one cant notice the voltage fluctuations unless
1. wifi cloud data logging is present in stabilizer - and the sync rate needs to be like every second(which i have) unlike their standard server which updates every 30 seconds.
2. monitoring the output voltage with some other device, eg. wifi connected solar inverter/ sonoff pow, etc to see any spikes/sags
3. actual output tested with a oscilloscope - best one
4. observing the tubelights / bulbs for slight flicker

there are times when the PWM is going off and restarting as per the device logs. in that time the output =input voltage. could be a DSP hangup. tech has told me many newer units are facing this voltage fluctuating issue. and yes, pasting a QC OK sticker on the cabinet isnt enough. one of the bolts on the heatsink for the wires were loose when the unit came. so ... i think numax is not the one even though cost is less...previously igbts used to fail itseems..now they replaced that with better ones and facing this voltage issue.

Currently Fuji Electric P2hf 40G120HD 31330 IGBTs are used in my unit.

tublights flicker corresponding to this..fan noise from solar inverter..the vibrating/buzzing from transformer
relying on the front display

I had noticed my LED lamps flickering only during power outages and wondered if the output voltage from my inverter was sagging.

Monitoring via Sonoff+HomeAssistant reveals that sure enough the inverter output at the start of the outage around 7.30 am is around 220V and sags to about 218V from around 10.15am until about 12.45 pm when the mains supply comes through and the voltage goes back to the stabilized 220-240V range.

Since you mentioned inverter, it might be worth a shot to check if your bulbs/tubelights only flicker when on inverter and not when on mains.

 

[kartechnology]

I had noticed my LED lamps flickering only during power outages and wondered if the output voltage from my inverter was sagging.

Monitoring via Sonoff+HomeAssistant reveals that sure enough the inverter output at the start of the outage around 7.30 am is around 220V and sags to about 218V from around 10.15am until about 12.45 pm when the mains supply comes through and the voltage goes back to the stabilized 220-240V range.

Since you mentioned inverter, it might be worth a shot to check if your bulbs/tubelights only flicker when on inverter and not when on mains.

View attachment 85063

having flicker in inverter is normal, but not in mains/grid mode under static stab.. without static stab its fine without flicker.
under static, voltage remains 228-230 but lights flicker.

I have contacted MEDI regarding this issue. since they are the ones who designed and developed this technology to manufacturers, there are lot of QC's missed out and bad manufacturing, leaving out copper tracks in refurb board, and the board was straight from a 3phase 5kva unit..means that board capacity is upto 5kva and they want me to use that in a 7.5kva. igbts were no-name brand (TGAN?).


I hope they will help me out.

numax = big no

 

[Musicforsalvation]

so they sent a refurb board. but seems like the dsp chip which can be swapped out is the culprit.
I will see till evening and swap out the new board with the refurb dsp and see.

can anything be done for this? i have spent 40k on this bad company...even troubleshooting they are unable to do properly. since i've worked with the parent r&d team i have some idea where things are going wrong... have a lemon makes me feel bad. i would be happy to get a refund.

PS: the dsp chip which was tied to the motherboard with a zip tag itself was loose and dsp was also not seated fully.. great QC..

It's good that you have knowledge of the technology of this system, but I don't think you should invest time and effort to try to repair it yourself. In a brand new system, such failures and shortcomings should not be justified or acceptable. Instead of giving you a refurbished board, they should have given you a completely new card or even a replacement system. I think you should return the system to Numax and get a refund because I don't believe it is your responsibility to fix the critical problems in the system that they have provided.

 

[kartechnology]

It's good that you have knowledge of the technology of this system, but I don't think you should invest time and effort to try to repair it yourself. In a brand new system, such failures and shortcomings should not be justified or acceptable. Instead of giving you a refurbished board, they should have given you a completely new card or even a replacement system. I think you should return the system to Numax and get a refund because I don't believe it is your responsibility to fix the critical problems in the system that they have provided.

i'm waiting for the designer to contact numax on this issue. will talk to numax tomorrow regarding refund...that can only give peace of mind. definitely they will not be willing to refund.

 

[kartechnology]

It's good that you have knowledge of the technology of this system, but I don't think you should invest time and effort to try to repair it yourself. In a brand new system, such failures and shortcomings should not be justified or acceptable. Instead of giving you a refurbished board, they should have given you a completely new card or even a replacement system. I think you should return the system to Numax and get a refund because I don't believe it is your responsibility to fix the critical problems in the system that they have provided.

Update
After deep diagnosis, It seems that many units face this issue in different grid power/places where harmonics are high,
Numax agreed to send me a complete new unit with more filters for harmonics and EMI/RF filter as well at the input, to check if that can sort the issue or will take back the units and refund me the amount. after contacting Mr. Boopathi, managing partner of numax, he has a lot of experiences with this issue, and explained me everything in detail,. lets see what happens.

the unit after extensive data logging revealed that it is unable to sense the correct input voltage due to harmonics, and load% shooting up to 150% triggering overload with no load connected due to noise from the mains.

 

[kartechnology]

having flicker in inverter is normal, but not in mains/grid mode under static stab.. without static stab its fine without flicker.
under static, voltage remains 228-230 but lights flicker.

I have contacted MEDI regarding this issue. since they are the ones who designed and developed this technology to manufacturers, there are lot of QC's missed out and bad manufacturing, leaving out copper tracks in refurb board, and the board was straight from a 3phase 5kva unit..means that board capacity is upto 5kva and they want me to use that in a 7.5kva. igbts were no-name brand (TGAN?).


I hope they will help me out.

numax = big no

the copper track missing board wasn't meant for my device. the service team had mixed up my board with a lower kva unit. but not all would identify things like me.

 

[kartechnology]

I am using NKB 5kva for approx 1.5 years. No issues so far and cannot hear any noise from mlp. Input voltage on an average is 245v touching 252v occasionally. Output correction is 230v or 231v.
Will update after a year regarding durability.

can you open the unit and share some pics? the filters and igbts used?

 

[kartechnology]

They must have a reason behind their pricing, best to ask them directly. They also gave a detailed test report of the unit before sending it. There is a very low noise from the unit (5KVA rated), I feel its not significant, although YMMV depending on your hearing sensitivity. Actual Input voltages vary between 229-252 volts, that is what I have randomly observed.

could you also open the unit and share some pics if possible? filters and igbts,
also please share test report if you still have it

 

[sayan00]

could you also open the unit and share some pics if possible? filters and igbts,
also please share test report if you still have it

I am scared to open up such systems, honestly i have no idea how to judge components by pictures. Also if anything goes wrong I will be left without a stabilizer. Maybe its a simple job but I wont be able to do it.

 

[sayan00]

Test Report

 

[kartechnology]

I am scared to open up such systems, honestly i have no idea how to judge components by pictures. Also if anything goes wrong I will be left without a stabilizer. Maybe its a simple job but I wont be able to do it.

just the cabinet, 4 screws usually, its okay thanks

 

[COOLDUDE7808]

Update
After deep diagnosis, It seems that many units face this issue in different grid power/places where harmonics are high,
Numax agreed to send me a complete new unit with more filters for harmonics and EMI/RF filter as well at the input, to check if that can sort the issue or will take back the units and refund me the amount. after contacting Mr. Boopathi, managing partner of numax, he has a lot of experiences with this issue, and explained me everything in detail,. lets see what happens.

the unit after extensive data logging revealed that it is unable to sense the correct input voltage due to harmonics, and load% shooting up to 150% triggering overload with no load connected due to noise from the mains.

Not an expert on these things ....but from what your saying the power coming to your mains is so bad that Stabilizer in its current configuration could not read the input voltage ? . Which city are you staying in ?

 

[Nitin K]

can you open the unit and share some pics? the filters and igbts used?

I am out of
town . Anyways I wouldn't understand the hardware part of it.

 

[kartechnology]

Not an expert on these things ....but from what your saying the power coming to your mains is so bad that Stabilizer in its current configuration could not read the input voltage ? . Which city are you staying in ?

Its not about that the voltage is bad. The quality is good(220-250v, no sudden sags or spikes, gradual rise and fall over the day). But there is something called as Harmonics, just like noise due to the nearby electrical loads or the loads(VFD like inverter AC also cause it, some solar inverters,) in the home,. This stabilizer is quite sensitive to it and needs additional filtering at the input and output to reduce the harmonics. In general many of our electrical appliances like inverter AC will be having filters at the input for this purpose so that it wouldn't cause erratic behaviour.

I think nkb is including additional filters at the input, going by their block diagram on their website. So that's why I wanna see the internals.

TSI power has static stabilizers which do work in such conditions but the cost is very high.

Even the static Stabilizers have capactors added inside the unit separately which act as filters just for reducing the harmonics generated by itself.

Another reason to use static instead of servo is idle power draw. I observed this 7.5kva draw 0.9 amps on idle, and a 10kva servo draws 1.4A on idle around 100watts higher.

A week has passed with lot of time debugging this

 

[Musicforsalvation]

Update
After deep diagnosis, It seems that many units face this issue in different grid power/places where harmonics are high,
Numax agreed to send me a complete new unit with more filters for harmonics and EMI/RF filter as well at the input, to check if that can sort the issue or will take back the units and refund me the amount. after contacting Mr. Boopathi, managing partner of numax, he has a lot of experiences with this issue, and explained me everything in detail,. lets see what happens.

the unit after extensive data logging revealed that it is unable to sense the correct input voltage due to harmonics, and load% shooting up to 150% triggering overload with no load connected due to noise from the mains.

This explanation appears to be just an eyewash and dilusional. How can grid supply in domestic area be so full of harmonics that the stabilizer doesn't work. If such is the case then forget about their systems working in industrial areas where you have all sorts of harmonics generating non linear loads operating at multiple industries in that area.
Transformer of this small capacity wouldn't make such buzzing unless it's poorly made.

Also what is their explanation about the loose bolts, improper mounting of DSP and non branded igbt used?

 

[kartechnology]

This explanation appears to be just an eyewash and dilusional. How can grid supply in domestic area be so full of harmonics that the stabilizer doesn't work. If such is the case then forget about their systems working in industrial areas where you have all sorts of harmonics generating non linear loads operating at multiple industries in that area.
Transformer of this small capacity wouldn't make such buzzing unless it's poorly made.

Also what is their explanation about the loose bolts, improper mounting of DSP and non branded igbt used?

Yes, it can't work in industrial areas. For that transformer issue they've not seen it before and hence sending a new unit and not the board alone.. and yes, QC issues, and non branded igbts .. These are real issues...

If the second unit also doesn't work, i have to test this harmonics theory by purchasing a stabilizer from nkb,sun power or any other manufacturer, which i don't have the energy to do so

 

[Musicforsalvation]

Yes, it can't work in industrial areas. For that transformer issue they've not seen it before and hence sending a new unit and not the board alone.. and yes, QC issues, and non branded igbts .. These are real issues...

If the second unit also doesn't work, i have to test this harmonics theory by purchasing a stabilizer from nkb,sun power or any other manufacturer, which i don't have the energy to do so

Power analyser will do the harmonics testing job for you. Or maybe you can ask numax to check it out at your place to support their theory. They may be having the tools to analyse the incoming power. This maybe is the best way to isolate the root cause of the issue you have faced. It is highly unlikely to have harmonic distortion to such an extent that it disturbes the stabilizer's functionality.