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Old 03-25-2008, 10:56 AM   #31
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I would agree with Inphase 77 line to neutral would be 240 volts... 340/sqrt2 = 240 volts. The equipment would function properly.

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Old 03-25-2008, 10:58 AM   #32
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Originally Posted by CowboyAndy View Post
So what if you hooked something like a saw to it...
A saw would run really fast for a short time, then poof! When you double the voltage, with everything else being equal, you double the current. This means that the total amount of power increases by 4. To borrow jrclen's analogy, but slightly corrected, a 100 W lightbulb becomes a 400 W lightbulb. Things aren't generally designed to handle a 4x power increase.

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Old 03-25-2008, 11:15 AM   #33
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Andy

A lot of these type questions are easily answered by using the equations of the electrical pie. You should familiarize yourself with it. You will need to be good at manipulating these equations when taking tests and other field work.
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Old 03-25-2008, 01:17 PM   #34
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Originally Posted by InPhase277 View Post
Good luck finding a 2 phase supply around here! I think there may still be some small isolated pockets of 2 phase in Pittsburgh or Philidelphia, but major 2 phase distribution in the U.S. went out in the 40s.

But anyhow, I'm gonna say that the since the line voltage in your question is 240 V, that the equipment would function properly, assuming the supply could deliver the necessary current.

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Originally Posted by Stubbie View Post
I would agree with Inphase 77 line to neutral would be 240 volts... 340/sqrt2 = 240 volts. The equipment would function properly.
Correct & correct . It's good to see that there are still some people who can "work things out".
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Old 03-25-2008, 01:21 PM   #35
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You are pretty good at it yourself mate....
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Old 03-25-2008, 02:14 PM   #36
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Originally Posted by InPhase277 View Post
To borrow jrclen's analogy, but slightly corrected, a 100 W lightbulb becomes a 400 W lightbulb.
InPhase277
Ooops. I knew I should have figured it out before posting. I stand corrected.
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Old 03-25-2008, 05:03 PM   #37
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Electric motors vs. voltage gets interesting. In this case it would depend on the type of motor.

All electric motors are 'balanced', so to speak. There's a balance between the amount of iron in the stator (the outside part with the wire wound on it), and the amount of copper . Same with the rotor (the part that turns). All must be balanced to a specific voltage. Current will vary with load.

There are basically 2 types of motors we deal with mostly. Universal and induction. Varying voltage will have different effects on each type.

The universal type is easily identified by the existence of brushes. Usually found in portable equipment because of its high horsepower to weight ratio. Speed varies widely with load and voltage. This type can handle severe undervoltage (with reduced speed and power). however, not much overvoltage will burn up the brushes quickly. If you hit a 120 volt universal motor with 240, most likely it'd blow one of the brush wires apart. Quickly.

The induction type is heavier, doesnt have brushes (a very few do for starting), relatively constant speed, and current varies widely with load. The biggest advantage here is a universal motors' brushes will only last a couple of hundred hours. An induction motor will run many thousands of hours with no maintenance at all. If you hit a 120 volt induction motor with 240 (it happens occasionally), it'll draw about 30 times its rated current, and almost certainly trip the breaker feeding it. If it's capacitor start, it might blow the end off the capacitor.

In either case, there's way more magnetism generated in the copper part of the windings than the iron part can handle. Current goes into the stratosphere, the weakest part overheats quickly, and burns up.

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Old 03-25-2008, 05:11 PM   #38
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Does anybodies head hurt besides mine???? I find it interesting how these type threads cause headaches.......
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Old 03-25-2008, 10:21 PM   #39
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I have had very little experience with motors. I should say that I have had little experience in troubleshooting motors. It has always been an interesting point of the trade to me, but so few opportunities come up to confront them. Not to mention a chance to learn from an experienced hand.

Great info.

The only thing I do really well is bend pipe.
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Old 03-25-2008, 11:01 PM   #40
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Not a bad days work Goose....
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Old 03-25-2008, 11:24 PM   #41
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What would happen if you took a straght 240v circuit - just 2 hots - and hooked them to a 120v device, hooking one of the hots to the neutral?
You sawsall would run really fast




240V air handler in an attic with a 120V recep and pigtail for disconnect if you were wondering.
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Old 03-26-2008, 08:44 PM   #42
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Not a bad days work Goose....
Thank you. You should see what I can do in two days.

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