3 Phase Question

[tshirtman]

I recently purchased a large dryer for use in the screen printing business. When the electrician installed it, he mentioned that if it was 3 phase instead of 2 phase that it would have saved me a lot of money on my electric bill. What is the difference in 3 phase and why is it less expensive to operate.

[LazyPup]

Regardless of whether you have single phase or three phase power all energy requirements are measured in WATTAGE. We are then charged for power in units called Kilowatt hours, which is an amount of energy equal to 1000watts for a period of 1 hour. Your utility provider may offer a different rating structure for 3ph. service but as a rule it would not change.

There are some technical advantages to 3phase, such as a more balanced load on the electrical service equipment and 3ph electric motors tend to run a bit cooler, but unless you already have 3ph service supplied to the structure, converting to 3ph can be an extremely expensive proposition which would require an entirely new service entrance system from the pole down, and it could require having a separate transformer mounted on the utility line.

[HayZee518]

A company called Grizzly Imports has a rotary convertor for making three phase from a single phase line. It is basically a motor and electronics that takes 230 1 phase and creates a third leg for three phase.

[HayZee518]

a three phase line consists of three windings spaced electrically 120 degrees apart. if you can picture a motor starting to turn, at one point the voltage starts at "zero" then rises to the 90 degree portion of the waveform, then back down to the reference line at 180 degrees. at this point another winding's voltage starts upward pulling the motor rotor along with it until it reaches its 180 degree mark and the third line picks up at its zero point. when the last winding reaches 180 degrees, the first winding starts upward again. In esssence the rotor is always trying to catch up with the rotating magnetic field. where it can't its called "slip" and manifests itself in the form of heat. a two phase motor's windings are 180 degrees out of phase with the other. so you got two pulls instead of three.