I just bought an LCD TV from Tesco which says (in 2 places) it is 70W. By my sums this should draw 0.3A at 230V (or 0.6A at 110V) therefore a 1A fuse is fine. However, right next to the power rating it says "1.5A" and the supplied plug has a 5A fuse in it. Am I being stupid!??
Power / Current Rating
- Thread starter JasonW
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70w is probably the average consumption
you have inrush /start up currents that are quite high
because it has an internal fuse to protect the tv the fuse in the plug is rated to the cable
if that was me i would use a 3 amp in the plug
you have inrush /start up currents that are quite high
because it has an internal fuse to protect the tv the fuse in the plug is rated to the cable
if that was me i would use a 3 amp in the plug
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Most items are now designed for whole of Europe and we are the only one to have ring mains and fuses in the plug so any protection required for the TV will be in the TV itself and the fuse in the plug is only to protect the cable.
Most TV's have a switch mode power supply and these work by converting the input voltage to DC and it is used to charge a capacitor then turned back to high frequency AC then transformed down to voltage required converter back to DC and charges another capacitor and is sampled and the low voltage parameters are changed to ensure the extra low voltage is correct.
Charging the two capacitors means on switch on quite an inrush of power.
However the curve on a fuse time / current for it to blow will allow quite a large over current and for a 13A fuse to blow often the B32 MCB will trip first and that needs 160A to trip the magnet part of the trip.
Although 1A, 2A, 3A, 5A, 7A, 10A and 13A fuses are made since they only protect the cable it is considered 2 sizes is all that is required the 3A and the 13A and 1mm² and above has 13A fuse and below 1mm² has a 3A fuse and Table 52.3 does not permit less than 0.75mm² cable to be used anyway.
My TV has three ratings one for standby less than 1W one for when used as a digibox for recording I think around 13W and when for when screen is lit around 115W it states in instructions "Average use" but the bedroom With a 100v to 250v inverter at 100v a surge of 1.5A is quite normal i.e. double normal use.
I am surprised at it being fitted with 5A fuse that is a non preferred size I would have expected to find a 3A fuse but either would protect 0.75mm² cable.
As to wattage of course it is not volts times amps that is VA it is volts times amps times power factor correction and since no pf is declared one can't work out between watts and amps at given voltage on an AC circuit.
Without considering the difference in power for a white screen to black screen the audio has around 20W output so must vary that much at least.
Most TV's have a switch mode power supply and these work by converting the input voltage to DC and it is used to charge a capacitor then turned back to high frequency AC then transformed down to voltage required converter back to DC and charges another capacitor and is sampled and the low voltage parameters are changed to ensure the extra low voltage is correct.
Charging the two capacitors means on switch on quite an inrush of power.
However the curve on a fuse time / current for it to blow will allow quite a large over current and for a 13A fuse to blow often the B32 MCB will trip first and that needs 160A to trip the magnet part of the trip.
Although 1A, 2A, 3A, 5A, 7A, 10A and 13A fuses are made since they only protect the cable it is considered 2 sizes is all that is required the 3A and the 13A and 1mm² and above has 13A fuse and below 1mm² has a 3A fuse and Table 52.3 does not permit less than 0.75mm² cable to be used anyway.
My TV has three ratings one for standby less than 1W one for when used as a digibox for recording I think around 13W and when for when screen is lit around 115W it states in instructions "Average use" but the bedroom With a 100v to 250v inverter at 100v a surge of 1.5A is quite normal i.e. double normal use.
I am surprised at it being fitted with 5A fuse that is a non preferred size I would have expected to find a 3A fuse but either would protect 0.75mm² cable.
As to wattage of course it is not volts times amps that is VA it is volts times amps times power factor correction and since no pf is declared one can't work out between watts and amps at given voltage on an AC circuit.
Without considering the difference in power for a white screen to black screen the audio has around 20W output so must vary that much at least.
C
ChrisFrost
Black screen to white screen won't make any difference on an LCD. It would on Plasma and CRT because they draw more current on a white screen, but LCD has a fairly continuous power requirement regardless of the screen content.
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Surprising how much difference dynamic contrast can make in power usage..
C
ChrisFrost
Interesting... Have you got some figures that show the impact with a conventionally lit LCD screen?
I don't have figures for a TV handy, but there are numerous examples of min/max power consumption available for smaller LCDs.
A few examples:
http://www.prad.de/en/monitore/review/2010/review-dell-u2410-part3.html#Power
http://www.prad.de/en/monitore/review/2010/review-samsung-p2250-part3.html#Power
http://www.prad.de/en/monitore/review/2010/review-eizo-s2433wh-bk-part4.html#Power
This is LED backlit, lower overall consumption, same swing between minimum and maximum figures:
http://www.prad.de/en/monitore/review/2010/review-acer-s243hlbmii-part3.html#Power
Power consumption is relatively low anyway, however the difference between minimum and maximum brightness is significant.
C
ChrisFrost
From your links I can see how it's possible to set up an LCD TV in different ways that affect power consumption. What's missing though is a graph or chart that shows Power Consumption vs Time once the TV is running with standard video content.
Dynamic contrast will alter the backlight level, but doesn't that cut both ways?; Lower consumption in dark scenes but higher consumption in bright scenes.
Dynamic contrast will alter the backlight level, but doesn't that cut both ways?; Lower consumption in dark scenes but higher consumption in bright scenes.
The backlight level should never increase beyond the setting you supply.
Such a graph would be interesting, but I haven't seen one. I'll keep my eyes open, but perhaps you should email the PRAD guys and suggest they include one?
C
ChrisFrost
Bit of a can of worms this...
In order to get the best effect from Dynamic Backlight - both in terms of improved contrast and the greatest power saving - then the backlight must be on a fairly high level - which is going to increase power consumption
Setting a lower backlight level will reduce power consumption, but also hamstring the effectiveness of any contrast boost at low IRE levels. IOW the 20:000+:1 contrast ratio boasted about is reduced to a real figure of maybe 1000:1 or less.
And since the vast majority of CCFL illuminated LCD TVs are still edge lit then the opportunity to dim portions of the screen backlight doesn't exist, so to make any meaningful contribution to power saving then you'd need to be watching films like Alien - predominantly dark scenes - rather than the normal TV fair that we consume...
It's a kind of damned if you do, damned if you don't scenario. Perhaps Dynamic Contrast should improve power consumption, but the reality is there are so many caveats that the benefits are debatable outside of lab conditions.
In order to get the best effect from Dynamic Backlight - both in terms of improved contrast and the greatest power saving - then the backlight must be on a fairly high level - which is going to increase power consumption
Setting a lower backlight level will reduce power consumption, but also hamstring the effectiveness of any contrast boost at low IRE levels. IOW the 20:000+:1 contrast ratio boasted about is reduced to a real figure of maybe 1000:1 or less.
And since the vast majority of CCFL illuminated LCD TVs are still edge lit then the opportunity to dim portions of the screen backlight doesn't exist, so to make any meaningful contribution to power saving then you'd need to be watching films like Alien - predominantly dark scenes - rather than the normal TV fair that we consume...
It's a kind of damned if you do, damned if you don't scenario. Perhaps Dynamic Contrast should improve power consumption, but the reality is there are so many caveats that the benefits are debatable outside of lab conditions.
M
Mickymoody
I suppose by UK regs, that a 5A fuse is good, as there is also an internal fuse rated far shorter. You seem to be discounting incoming power fluctuations, as opposed to an internal issue. When the internal fuse might be rated at 1A, sand fuse, or quick blow? So yes you are being stupid. You asked.
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