Ups as inverter But problem occur

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RajivConfident

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When I connect the CFL bulb in UPS of the computer.CFL bulb automatically turned off.But computer run normally by same ups.
What can i do?
 

My guess: The UPS probably produces square wave output and the lamp doesn't like it. (Some sort of self-resonating system perhaps? Working only on sine wave?) Possible solutions: get a different lamp, get a different UPS with sine wave output (expensive and might be hard to find), install filter of some sort between the UPS and the lamp.
 

chuckey said:
230V mains is about 330V peak which powers the inverter for the bulb. With a modified sine wave the peak voltage is only 230V, so the inverter will produce a lower voltage which will not strike the tube.
Frank
Click to expand...
No.
A modified sinewave is a modified squarewave with positive and negative parts that almost equal the peak voltage of an equally powerful sinewave.
You are talking about a pure squarewave that has its peak voltage at 0.707 times the peak voltage of a sinewave so that their average powers are the same.

Here are waveforms of 120V sinewave, squarewave and modified sinewave signals. When the 120V RMS sinewave is increased to 230V RMS then its peak is 325V. The "230V" squarewave has peaks at 230V and the modified sinewave has peaks at 288V:
 

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The power of ups is 12V 7.5A.When i connect bulb directly bulb works normally but when i connect it in output terminal of ups it turned off within a second.
Also when i use charger circut other smaller bulb also works normaly.
Is there any idea to connect cfl directly?
 
RajivConfident said:
The power of ups is 12V 7.5A.When i connect bulb directly bulb works normally but when i connect it in output terminal of ups it turned off within a second.
Click to expand...
Power is not 12V 7.5A. Power is Watts or VA. A battery is also not 7.5A, it might be 7.5Ah which is its capacity, not its maximum current.

Is it the CFL bulb that you connected directly?
The bulb works normally when it is connected directly to what?
Is the battery for the UPS old and weak? What is its capacity in Ah?
 

Yes i connect the CFL bulb directly on the battery.
The bulb works normally when it is connected directly to battery.
battery go UPS is new which run computer normally. its capacity is 12V/7.5Ah.
 
Since your CFL bulb works normally when connected directly to the 12V battery then why are you connecting it to the much higher output voltage of the UPS?
What is the output voltage of the UPS? Isn't the UPS output a high AC voltage and isn't the battery output a low DC voltage?
 
thannara123 said:
I meant that the UPS needs to run minimum load . CFL has about 10-30 watts only , ..
Click to expand...
Why would a UPS need a minimum load? It has a very small low power battery which would produce only 48W for 1 hour.

It sounds like he is connecting a 12VDC CFL to the output of a 230VAC UPS so of course the UPS is overloaded.
 

Most of the UPS is automatically OFF ?shutdown when it haven't enough load .. to save battery . he mentioned that he is using a computer UPS . so a computer UPS hasnt only 48 watt . it may be 400 watt or above .
 

400W from a UPS is a load on the 12V battery of at least 500W so its current will be 500W/12V= 42A. His little 7.5Ah battery cannot supply only 15A at 12V but can supply 7.5A at 12V for almost 10 minutes. See this graph:
 

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75 A with 12 volt battery can provide about 720 watt for 7.5 minutes . right ?
 

thannara123 said:
75 A with 12 volt battery can provide about 720 watt for 7.5 minutes . right ?
Click to expand...
For a load of 720W the 12V battery must supply 60A. A lead-acid car battery with a capacity of 60Ah can supply 60A at 12V for 7.5 minutes, only when the battery is new.
 

jolly jacob said:
Is 12V/60Ah battery can provide only 7.5min running time at 720W load?
Click to expand...
Yes. The battery voltage is dropping and at 7.5 minutes it drops to 12V. At 25 minutes the battery is dead at 11V.
 
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