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Old 3rd December 2010, 03:22   #1741
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Originally Posted by Guite View Post
The inverter I use is sine wave. I have tried putting an UPS ahead of the inverter, and it was not a good exprience. Picture this:- light goes off in the middle of the night and the UPS goes beep beep beep beep ....
This is getting common, When you have a sine wave inverter feeding the UPS, the power cut doesn't lets UPS detect restoration of current which is coming from your home ups/sine wave inverter.

Can some one shed some light on this please......

Is it that UPS in not able to digest a better energy graph
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Old 3rd December 2010, 12:21   #1742
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Have never used a LCD yet, so couple of questions - LCD's come in 16:9 aspect ratios and CRTs in 3:4, right? Or do they make CRTs in 16:9 ratio too?

One of my gripes with CRTs is the 4:3 aspect ratio means that much of the content appears with large black area on top and bottom (so that the whole image can fit) which is a criminal waste of screen real estate.

I assume that does not happen with LCDs right?

Furthermore, I was shocked to hear from both the Onida technicians who visited our place that LCDs last only upto 2 or at the very max 3 years. This is like their rated life span and the period after which they may break down! CRTs inherently have much longer life spans. Further the PCB of CRTs an be repaired, whereas for LCDs they just have to replace them, which of course costs much more. Are these statements true? If yes, then I would definitely not be inclined to spend so much on a larger screen LCD tv that can only be expected to last 2 - 3 years.
Never heard of CRT in 16:9 ratio.

It all depends on the source image. Normal TV is 4:3, while 70mm can be 2:1. So even wide screen LCD will not be filled top to bottom at times.

The life of the LCD is practically infinite. What deteriorates is the back light illumination. In normal LCD it is fluorescent source. In LED it is LED.
I have been using LCD monitors for the last six years. My 19" monitor is over five years old. Over time it has dimmed a little, but nothing to worry about. Maybe in TV they use less expensive back light which may dim faster, but it cannot just blow. Hence the life of an LCD TV cannot be specifically fixed to 2 or 3 years.

Regarding repairs. In a LCD the most expensive part is the panel, which today comes as one integrated package containing the LCD, the back light and row & column drivers, all sealed. Hence any repair requires extensive tooling and is done in the factory. As disassembling, repairing and reassembling such a complicated package is expensive the current trend is to throw away (at your expense) and replace. The exception is very large panels where the cost of the panel justifies repair costs.

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Originally Posted by carboy View Post
Whose picture quality is better?
Are you comparing LCD with CRT or LCD with LED or LED with CRT?

Because I don't believe LCD is better than CRT.
It is easier go get exact colour on a CRT compared to LCD. Further, most of the higher end CRT monitors have a greater brightness range compared to LCD. You hear a lot of "great blacks" in LCD, an issue which was not there in CRT, because there is always a spill over in back lighting which affects black (zero light!). The response time of the CRT monitor depends on its electronics, which can be practically instantaneous, while the response time in LCD would depend on the LCD technology and can vary from quite slow to moderately fast, but rarely in sub milliseconds as in CRT, hence you can get much faster refresh rates in a CRT compared to LCD, especially for very high resolution displays (> 2kx1.6k pixels)

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Originally Posted by Guite View Post
Bringing up a slightly old topic. I have got this 4kva Bluebird voltage stabiliser, the type most commonly used with ACs. The front panel description is: "IC controlled electronic voltage corrector" and "specially designd for Air Conditioner only". Now, note the words "for AC only".

This is important because I want to put it ahead of my home inverter, so all electrical load on my inverter circuit will pass through this stabiliser. This will include lights, TV, PC, music system, etc. Can there be any harm in using this 'for AC only' stabiliser for normal home appliance loads?

I need to do this because in case of high voltage the home inverter (APC) cuts off mains supply and provide power from battery. In case it helps, the bluebird stabiliser specs are: input 170 to 280 volts, output 195 to 245 volts.

Any input will be appreciated.
First of all as stated an AC stabiliser has a timer to prevent starting the AC instantaneously. This is to prevent damage to the compressor if the light went for a very short duration. Further as AC starting current is three to four times its running current, starting a lot of AC at a time; as in an office; would blow the main fuse due to starting surge.

A mechanical stabiliser is slow, hence it cannot prevent voltage surges. In my case I have seen equipment blow because the stabiliser could not keep up with the change in mains voltage, which at times can go from 190 to 240 in less than a second. The stabiliser though will help you stabilise constant low/high voltage to the UPS. What you need is a "high voltage cutoff" ahead of the UPS, to prevent the surges propagating through the system to your equipment.

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Originally Posted by adityamunshi View Post
How come CVTs and Digital voltage regulators arent recommended ?
I thought servo stabilizers were old tech and had been replaced by CVTs.
CVT is a saturated core device, meaning that after the threshold voltage is achieved no more voltage transformation will occur, that is there will be a constant voltage at the output. The only downside is waveform distortion and low efficiency, which results in over heating and humming.

Servo stabilisers are still used in industry to correct long term voltage variation. I have seen advertisements for selling 100KVA and larger servos. Their USP is high transfer efficiency (low loss), hence lower cost of operation. Other forms of stabilisers are either stepped transformer or electronic controlled AC-DC-AC devices which have lower power efficiency, but better control, hence used for low power applications.

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Originally Posted by ghpk View Post
This is getting common, When you have a sine wave inverter feeding the UPS, the power cut doesn't lets UPS detect restoration of current which is coming from your home ups/sine wave inverter.

Can some one shed some light on this please......

Is it that UPS in not able to digest a better energy graph
Could not fathom the question. Is it that the UPS does not detect when mains is off/restored, or that UPS goes on battery when mains is off and inverter is on?

A sine wave inverter, if it delivers a true sine wave cannot be distinguished from the mains supply! Hence for all practical purpose the UPS will see the output from the inverter as normal supply.

It may be that in your case, the quality of waveform or the voltage output by the inverter is not considered by your UPS as "good quality" power, hence it is rejected. Note that an inverter is normally "line interactive" type device, that is when there is mains the input is routed directly to the output. It is only when the mains fails that the output is fed from the inverter.
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Old 3rd December 2010, 14:13   #1743
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Originally Posted by khoj View Post
In case you are still looking for one the links below will give you the contact details for Logicstat the company as well as their dealers in Noida.
Thanks. I have already bought Bluebird.

Quote:
Originally Posted by ghpk View Post
This is getting common, When you have a sine wave inverter feeding the UPS, the power cut doesn't lets UPS detect restoration of current which is coming from your home ups/sine wave inverter.

Can some one shed some light on this please......

Is it that UPS in not able to digest a better energy graph
The scenario I was describing is opposite, which is UPS feeding Inverter. In this case when mains goes off, the UPS goes beep beep, naturally.

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Originally Posted by Aroy View Post
First of all as stated an AC stabiliser has a timer to prevent starting the AC instantaneously. This is to prevent damage to the compressor if the light went for a very short duration. Further as AC starting current is three to four times its running current, starting a lot of AC at a time; as in an office; would blow the main fuse due to starting surge.

A mechanical stabiliser is slow, hence it cannot prevent voltage surges. In my case I have seen equipment blow because the stabiliser could not keep up with the change in mains voltage, which at times can go from 190 to 240 in less than a second. The stabiliser though will help you stabilise constant low/high voltage to the UPS. What you need is a "high voltage cutoff" ahead of the UPS, to prevent the surges propagating through the system to your equipment.
Thanks for the informative response. However, it seems my mention of UPS is confusing everyone, and in turn confusing me now! I was just responding to another member who suggested I use UPS (instead of stabiliser), which in my situation is not a practical proposition. My basic requirement is to supply normal voltage to the inverter.
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Old 3rd December 2010, 14:58   #1744
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Originally Posted by Aroy View Post
CVT is a saturated core device, meaning that after the threshold voltage is achieved no more voltage transformation will occur, that is there will be a constant voltage at the output. The only downside is waveform distortion and low efficiency, which results in over heating and humming.

Servo stabilisers are still used in industry to correct long term voltage variation. I have seen advertisements for selling 100KVA and larger servos. Their USP is high transfer efficiency (low loss), hence lower cost of operation. Other forms of stabilisers are either stepped transformer or electronic controlled AC-DC-AC devices which have lower power efficiency, but better control, hence used for low power applications.
What would be the difference in efficiency of a digital stabilizer vs CVT or servo ?
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Old 3rd December 2010, 16:16   #1745
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Originally Posted by ghpk View Post
This is getting common, When you have a sine wave inverter feeding the UPS, the power cut doesn't lets UPS detect restoration of current which is coming from your home ups/sine wave inverter.

Can some one shed some light on this please......

Is it that UPS in not able to digest a better energy graph
Aroy has already answered that very well. In short, don't believe what the companies tell you. If the UPS isn't accepting the input voltage, then most likely its not really giving a true sine wave output. Actually, this issue has been discussed somewhere on tbhp before, if not on this thread itself.

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Originally Posted by Aroy View Post
Never heard of CRT in 16:9 ratio.

It all depends on the source image. Normal TV is 4:3, while 70mm can be 2:1. So even wide screen LCD will not be filled top to bottom at times.

The life of the LCD is practically infinite. What deteriorates is the back light illumination. In normal LCD it is fluorescent source. In LED it is LED.
I have been using LCD monitors for the last six years. My 19" monitor is over five years old. Over time it has dimmed a little, but nothing to worry about. Maybe in TV they use less expensive back light which may dim faster, but it cannot just blow. Hence the life of an LCD TV cannot be specifically fixed to 2 or 3 years.

Regarding repairs. In a LCD the most expensive part is the panel, which today comes as one integrated package containing the LCD, the back light and row & column drivers, all sealed. Hence any repair requires extensive tooling and is done in the factory. As disassembling, repairing and reassembling such a complicated package is expensive the current trend is to throw away (at your expense) and replace. The exception is very large panels where the cost of the panel justifies repair costs.
Yes, I checked that up. Obviously the Onida repair guys seem to be pulling a fast one on me... but can't fathom their motive. Or maybe its just that they wan't to encourage people to go for CRTs, so that they get a chance to repair them and mess them up more, lol.

Does the same apply to laptop displays?

Quote:
It all depends on the source image. Normal TV is 4:3, while 70mm can be 2:1. So even wide screen LCD will not be filled top to bottom at times.
Yes, it is obvious that it would depend on the source image, but even if the source is 2:1, etc., the wasted screen area at the top and bottom would still be much less than what would happen on a 3:4 screen, right?

Last edited by Raccoon : 3rd December 2010 at 16:17.
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Old 4th December 2010, 12:09   #1746
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Originally Posted by adityamunshi View Post
What would be the difference in efficiency of a digital stabilizer vs CVT or servo ?
It seems that a "digital stabiliser" is an inverter with some added features. Some info Products

A CVT is a magnetic device devoid of any electronics.

A Servo is a continuously variable auto transformer, driven by minimal electronics (mainly voltage comparators).

Regarding Efficiency

1. CVT is generally 50-70%, depending on voltage difference between input and output. The lower the difference the better the efficiency.

2. Servo is generally 90-99%, again depending on the transformer design.

3. UPS/Inverter vary between 50-80%. The reason for low efficiency is that there are two circuits - AC-DC (charging) and DC-AC (inverter). The efficiency falls further due to the battery float charging requirements (charge to maintain the battery capacity even when not in use).
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Old 4th December 2010, 18:39   #1747
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Default Load carrying capacity

What is the load carrying capacity of an electrical equipment (which is typically rated in kva)? For example, how much watt can a 1 kva inverter/stabiliser/ups support? In an earlier post I had considered 80% power factor. But I myself am not sure.
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Old 4th December 2010, 18:55   #1748
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What is the load carrying capacity of an electrical equipment (which is typically rated in kva)? For example, how much watt can a 1 kva inverter/stabiliser/ups support? In an earlier post I had considered 80% power factor. But I myself am not sure.
That depends on the manufacturers method of rating. A purely resistive load like a normal bulb will have PF=1. Small single phase motors have PF=0.5 to 0.7. My APC 1500kVA ups rates it at 1kW resistive load! For all practical purpose transformers can be rated at PF=1. Beware that motors (AC, WM etc) can consume 3-5 times the running current when starting, so that the stabiliser should be able to support that load for a short time (transformers do, inverters do not)

So in the end, read the manufacturers fine print to find out what is the actual capacity!
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Old 4th December 2010, 20:29   #1749
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Hmm.... mixing both these threads got me confused. Is your problem solved guite. You said you connected the ups ahead of the inverter and it kept buzzering with power cut. Definitely it will buzzer when there is power cut. You can ask the technician to cut the supply to the buzzer if it annoys you.

Regarding the power factor, it depends on the manufacturer. You get anywhere between 1 to .75 or even less. Components are costly, manufacturers try to minimize the cost as much as possible and they have the excuse of power factor.

IF you ask the manufacturer you want power factor of 1 for a 1 kva product, they will give you 1.5 kva. That way you can load full 1000 watts. Of course they charge extra for that.
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Old 4th December 2010, 23:05   #1750
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Thanks Aroy and Chipz for the responses. Chipz, my problem was solved when I replaced the UPS with a stabiliser. As you can imagine, I used the UPS ahead of the inverter for only one night.
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Old 8th December 2010, 16:48   #1751
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Default Re: The Home Appliance thread

Quick brief about experiences with Onida:

Wrote two emails to their service id and also head office. No reply till that. Not even an auto-response.

Yesterday, they sent someone to take the whole tv (model: Oxygen Thunder 29") away to their service center. Today they call me and say there is no problem, and they have not experienced a single incident of the tv turning itself off even after keeping it on whole day. They wan't me to come to the service center tomorrow and check myself. I really don't think I have the time to do that... and nor do I think going there will be of any help.

Most likely, the set will start acting up after they deliver it back. They are still in total denial about the slight screen flicker that now occurs after they "fixed" it the 1st time.

So now in a span of about 3 years, the tv needed multiple service visits when in warranty and later they replaced it when they could not rectify it (after contacting the company). That was great... but now this replacement didn't even last 3 years.

Sad to think that Onida was once a market leader and was known to sell products that used to last. Seems things have changed with Onida too.

Onda = ineffective service, mediocre product quality, no response from company.

Though the picture quality was quite good while the set worked, lack of overall quality is quite apparent with things like the power switch failing 3 times in 3 years, poor quality and very poor design of remote (what do you expect form iBall?).

Rs. 450 for a single service visit (parts cost + labour extra, of course) does not help the case either. Though I don't know what other tv manufacturers charge. Do others also charge so much?

Guess we will just have to trash this one... and not touch Onida again.
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Old 8th December 2010, 17:34   #1752
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Question Re: The Home Appliance thread

I am being nominated for a short term assignment to UK and need to take a small pressure cooker this time. last time I was in UK, had a horrible time without the pressure cooker and coconut grater but this time I will be taking them along. Any good options available? Should I settle for the 3 lts cooker. I'll have to take a bag also suitable for the cooker. Most of the serviced apts in UK have hot plates than gas for cooking, so I need to buy a compatible cooker. The one with thick bottom.
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Old 8th December 2010, 17:41   #1753
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Default Re: The Home Appliance thread

Ghodlur@ Can you take a pressure cooker inside a plane. Once my dad was not allowed to take one with him...that was 5 years back.
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Old 8th December 2010, 17:55   #1754
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Ghodlur@ Can you take a pressure cooker inside a plane. Once my dad was not allowed to take one with him...that was 5 years back.
Do not carry in hand baggage, leave it in check-in luggage.
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Old 8th December 2010, 18:02   #1755
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Smile Re: The Home Appliance thread

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Ghodlur@ Can you take a pressure cooker inside a plane. Once my dad was not allowed to take one with him...that was 5 years back.
Absolutely , you can carry cooker but no pressure inside. . Recently my office colleague had carried it but unfortunately he left it behind for lack of luggage space.

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Do not carry in hand baggage, leave it in check-in luggage.
Yes, it would be carried in check in luggage. I heard that most airlines have reduced the check in luggage weight, dont know how much.
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