Reply by BroDave

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Posted on Power Tool voltage\amp question (Bandsaw)

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107 posts in 3811 days

#1 posted 12-30-2007 06:38 PM

OK, here is the difference between 120 and 240 volts.

A cycle, displayed as “Hertz” on the motor name plate, is nothing more than frequency, as in how many times something occurs. In this case it is how many times the electrons flow from point A and return to point A.

Think of it like this;

The cycle we normally would think of as circular should be thought of as peaks and valleys.

On a single phase motor, 120 volts, the voltage starts in the valley, bottom, and climbs to the Peak, the top, then falls back down. What happens is that the motor must work harder to maintain the rated HP or work load at every step in the cycle except at the very top.

Now 240 volt motors are powered by two wires of 120 volts each, when checked to ground.
So what we have is two separate cycles or sets of peaks and valleys.
The result is that while one cycle is at the peak the other is in the valley. as the cycle continues they change places. This means that a 220 volt motor has to work half as hard as a 120 volt motor to do the same amount of work. In other words it is more efficient consumption wise and uses smaller wire and breaker size.
The cost of addition wire and breaker offset the power savings for a while but eventually you realize a savings.

I know that was a very simple but for those that don’t deal with this type of thing it should help.

For more details on the “peaks and valleys” you can check this.

You can also see more about motors here.

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