220 and 120 volts

Discussion in 'General Electronics Chat' started by the_amnbusher, Feb 10, 2009.

  1. the_amnbusher

    Thread Starter New Member

    Feb 10, 2009
    Hi iam new here so hope iam making my question in the correct place. What iam wondering is do small appliances and power tools run more efficiently when using 220 volts verses 120 volts? It seems to me the power tools will dim the lights and bog down quicker when using 120 Thanks for any answers
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    For the same power rating (watts) the 220VAC device only draws 1/2 the current as a 120VAC device.
  3. triggernum5

    Senior Member

    May 4, 2008
    P=VI for resistive loads, so asaide from wire losses increasing with current not much changes there (although that reduced current is vital to alot of applications), but with 220V the slopes of the voltage/current waveforms are steeper which can have more signifigant advantage with inductive loads.. Either way, 220V wins I guess..
  4. Wendy


    Mar 24, 2008
    Except in the USA. 220 exists, but the usual output is 120VAC for almost everything.
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
    Most portable appliances use 'Universal' type motors.

    The efficiency of these does not depend upon voltage, but does increase with frequency so the American 60Hz kit has a slight advantage over the European 50Hz.

    The 120 volt machines are much safer than the 220v ones.

    Because of the higher current levels in the 120 volt machines they are heavier and bulkier than their 220 volt counterparts. This effect is partly offset in 60hz machines by the increased frequency.

    Efficiency is not usually a useful measure of performance however. This is because the efficiency varies significantly with mechanical load. By the very nature of their use the mechanical load on portable appliances such as drills, vacuum cleaners etc etc varies greatly. Further they are not often operated in conditions of maximum mechanical load.

    So it is more usual to talk about the torque (pun intended) developed by such a motor, which describes the available mechanical power in any given situation.

    Finally the higher the voltage, the lower the current and thus the lower the resistive wiring losses both within the machine and in the wiring leading to it or the heavier the gauge of wiring required. The smaller wiring gauge needed for the higher voltage leads to greater cost efficiency.
  6. mik3

    Senior Member

    Feb 4, 2008
    The efficiency of a machine does not depend on the supply used but on the machine itself. One reason 240V machines may be a bit more efficient is that they draw less current and may run cooler than the 120V ones. However, a 120V machine is designed to handle the larger currents so it is not a serious factor to worry about.