Any Electricians? (idle curiosity)

Discussion in 'OT (OFF Topic) Forums' started by MikeL, Nov 5, 2008.

  1. MikeL

    MikeL Hardcore MB Enthusiast

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    Hi,

    Can anyone tell me why Pioneer state a plug must be fitted with a 5 amp fuse on one of their DVD players.

    The player is a standard UK model 220/240V 14W / 2 core detachable cable.
    Would have thought 3 amp sufficient?

    Ta

    Mike
     
  2. merc man

    merc man Hardcore MB Enthusiast

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    depends on the model, some have a built in amplifier, and some require more power to process the signals ect, and also require the extra current draw to regulate all the componets inside the unit. 3 amp is ok but i would stick woth the reccomended amperage.
    hope that helps
     
  3. Will

    Will MB Club Veteran

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    I agree, a 5A fuse would be sufficient for over 1 kilowatt!

    A 3A should be fine IMHO, that's enough for 600/700W+, no DVD player would use that much power normally.

    Will
     
  4. whizzkid11

    whizzkid11 Hardcore MB Enthusiast

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    I fully agree Mike... 3A should be more than sufficient.

    Question is do they have 3A fuses where the Pioneer DVD players are manufactured?

    For anybody who may not know/is curious:

    Power (P) = Current (I) x Voltage (V)

    V in the UK is 240v - therefore the current rating for the fuse should be the next available denomination once you have divided the maximum power consumption of the appliance by 240.

    eg: a 600W appliance would use 600/240 = 2.5A and hence a 3A fuse would be ideal.

    At the same time, a 700W would be consuming 700/240 = 2.91A - however it would be recommended to use a 5A fuse even though theoretically a 3A would suffice.

    Apologies if I am preaching to the priests!

    rgds
    Was!
     
  5. Rory

    Rory MB Club Veteran

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    The only possible reason I can think of, and I'm really clutching at straws, is perhaps they've had issues with 3A fuses blowing on start up due to surges / inrush currents?
     
  6. grober

    grober MB Club Veteran

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    The DVD may well have an internal fuse/ fusible link to protect the circuitry in which case the plug fuse is rated to protect the appliance cable rather than the appliance itself. If the cable is rated at >5amp then a 5 amp fuse is OK.
     
  7. marcos

    marcos Hardcore MB Enthusiast

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    Voltage in the UK is 230v single phase and 400v 3-phase and has been for a number of years now or should be:rolleyes: , it will reduce down to 220v over the next couple of years to comply with Europe.
    Therefore 700/230= 3.04amps.
     
    Last edited: Nov 6, 2008
  8. verytalldave

    verytalldave Hardcore MB Enthusiast

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    Some electronic equipment needs to be fitted with a fuse which seems overly large. This is can be due to the fact that some items draw a large spike of current on turn-on and then settle down to only draw a a few hundred milliamps on normal operation. If you switch to a quick blow 3 amp type fuse, you may find it blows. A slow-blow delay type fuse would probably be OK but its normally beyond the expectations of the companies that produce the equipment to rely on the average member of public to be able to differentiate between these 2 types of fuses. So they go for the simple option and overate the recommended fuse value.
     
  9. Rory

    Rory MB Club Veteran

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    That's all plug fuses do - they prevent the cable from becoming the fuse and melting.
     
  10. Benzowner

    Benzowner Hardcore MB Enthusiast

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    That is unreal, I worked for the electricity board when we changed from 210v to 240v and I guess the same question will raise its head or should do, who pays for the additional electricity when the voltage is reduced, I guess we do, but its a con. Reduce voltage from 240 to 230 to 220 and a 3kw kettle will take longer to boil as will the dishwasher, washing machine etc.
     
  11. Stratman

    Stratman Hardcore MB Enthusiast

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    The Euro 220/240 Volt thingy was settled a while back in a true politicians muddle. They decided that we must all standardise to 220V, but the tolerance they allowed was sufficiently wide for 240V to meet the spec.

    Another example of individuals who on their own can do nothing, but when they get together they can authorititavely decide that nothing needs to be done.
     
  12. OP
    OP
    MikeL

    MikeL Hardcore MB Enthusiast

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    Thanks for all the answers (wow).

    So I had to know, 3x Pioneer DVDs, ranging from 2001 - new (the last two models are essentially the same the newer one having extra electronics).

    From oldest to newest 8w / 12w / 14w.

    I actually have come up with two theories.

    1) Internal Fuse

    2) The cable is detachable, so could be plugged in to a higher rated device - after all who checks fuses as long as the cable fits?

    Mike
     
  13. OP
    OP
    MikeL

    MikeL Hardcore MB Enthusiast

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    If the figure represents watts, there is a 2.5 stamped on the plug that inserts to the unit.

    Mike
     
  14. OP
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    MikeL

    MikeL Hardcore MB Enthusiast

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    OK, to draw a line under the subject before it gets boring - regarding the 3 players, the instructions for the newest model don't mention the fuse rating at all.

    So either they aren't worried, more dumbing down or they know nobody reads this stuff.

    Mike
     
  15. whizzkid11

    whizzkid11 Hardcore MB Enthusiast

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    1. can be checked with a screwdriver ... :)

    2. Most likely the cables were purchased from another cable supplier before Pioneer boxed the system prior to dispatch - in fact was probably done by the exporting or importing distributor to have the correct plug.
     
  16. grober

    grober MB Club Veteran

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    For PAT testing it would appear they have settled on a 2 fuse system with appropriate cabling. Either 3 amp or 13 amp.Guess it makes life easier? http://www.pat-testing.info/plug.htm
     
  17. Rory

    Rory MB Club Veteran

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    What did you actually do at the electricity board? I do hope it was nothing to do with electricity. :)
     
  18. Will

    Will MB Club Veteran

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    LOL ;)
     
  19. Diapason

    Diapason Member

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    The cost of a lower voltage supply

    Geoff,

    I think I can help here.

    Electricity meters measure the product of voltage, current and time, giving a figure in Kilowatt hours. This is a measurement of energy used. If the voltage is decreased, then - yes, the current decreases - and the kettle takes longer to boil. However, the total amount of energy used, and hence the cost, will remain the same. If this were not the case, then those at the end of a cable run - where voltages are subject to signficant depression within specified tolerances - would be paying more for their energy. They don't. Electricity meters measure energy = voltage x current x time.

    I hope that helps.

    Simon

    PS. An interesting discussion point may be the phase angle between voltage and current - and the devices that distort this. If you've ever wondered, for example, why there is a capacitor directly across the supply terminals of a flourescent tube - it's there to counter the effects of the inductor which is in series with the tube itself, and to ensure that the whole device appears to the electricity supply a near as possible like a pure resistor.
     
  20. agatward

    agatward Hardcore MB Enthusiast

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    Which is why the calculations given earlier in this thread actually give power measured in VA, not in Watts. For a DC supply, there is no difference, but for AC the IV phase angle has to be factored in too. For the cheap power supply included in most consumer electronics, there is usually very little in the way of power factor correction (i.e. very little bringing the angle close to zero). The circuitry required to do what is known as Active Power Factor Correction can be quite complex depending on the number of phases involved and the load on the output of the power supply. This is why, for example, PC power supplies that do active PFC are a lot more expensive than those with passive PFC.

    Switched-mode supplies (which most modern consumer electronics use) are notoriously bad for having a large IV phase difference due to the inductors used as part of the switching process. Very few consumer manufacturers bother with active PFC as it adds significant expense to the cost of the power supply.

    Another interesting point is the IV phase of a tungsten filament lamp (the ones before these new-fangled energy saving things). When attached to a dimmer, for part of the mains cycle they act as an inductor, and for part as a resistor (due to the way most modern dimmers work, switching at the zero-crossing point of the AC waveform).
     

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