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post #41 of 80 Old 08-13-2016, 03:12 PM
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Originally Posted by Steve Neul View Post
You say this but this was explained to me by a company that rebuilds electric motors. Then as far as power and heat I have seen this from first hand experience operating the same saw at 120v and 220v. There is a definite reduction in the saw motor generating heat at 220v and you can feel a slight power increase. There is a definite benefit to operating a saw at 220v if it is equipped.
Unfortunately you were misinformed, but it's not uncommon. Rebuilding motors is a mechanical occupation. They don't need any electrical background. The same is actually true for electricians. Most (but not all) have very little electrical knowledge.

This is not a new topic. I wrote Electricity in the Woodshop 20 years ago because of it. I invite you to read that, as it covers and explains all of the points you just stated. There was a time that if you Googled the word Electricity, this article was the first hit.

Because the windings are switched between either series connected or parallel connected, the voltage and amperage through each winding is the same regardless how they are configured to external configuration.
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post #42 of 80 Old 08-13-2016, 03:47 PM
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What a surprise!

I have often referenced your articles on static or explosions in dust collector systems in response to inquiries here. Thanks for showing up on this forum and please stick around. You have a wealth of knowledge to share.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #43 of 80 Old 08-13-2016, 03:55 PM
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Rick, I was once firmly in your camp, and I do have some experience with motors. But my thinking is shifting. The reasons are somewhat complex and completely off topic, so I posted those to a new thread, and I hope you will consider commenting.


http://www.woodworkingtalk.com/f12/w...detail-144018/
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post #44 of 80 Old 08-15-2016, 07:02 AM Thread Starter
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Well I had the chance to check the wire to the barn. 10-3. I was certain I purchased 8 ga wire and was so puzzled by it that I would have dug through old tax records for the wire receipt, except they were lost in a fire. I remembered that I had some extra wire stored in the back shed. I went digging and found a part of a spool of 8-3. Not enough left to run to the barn. So I did purchase 8-3, I just don't know what happened to it. Anyway, I am stuck with a 125 ft run of 10-3 to the barn. So. I will have to watch my amps draw a little closer. (In the winter, I run up to two water trough heater ats 1500 watts each.) The lights have all been changed to LEDs so that draw is minor.

So I guess i will need to rewire the connections to the motor to 120 volts and limit what is used simultaneously.
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post #45 of 80 Old 08-15-2016, 07:41 AM
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Well I had the chance to check the wire to the barn. 10-3. I was certain I purchased 8 ga wire and was so puzzled by it that I would have dug through old tax records for the wire receipt, except they were lost in a fire. I remembered that I had some extra wire stored in the back shed. I went digging and found a part of a spool of 8-3. Not enough left to run to the barn. So I did purchase 8-3, I just don't know what happened to it. Anyway, I am stuck with a 125 ft run of 10-3 to the barn. So. I will have to watch my amps draw a little closer. (In the winter, I run up to two water trough heater ats 1500 watts each.) The lights have all been changed to LEDs so that draw is minor.

So I guess i will need to rewire the connections to the motor to 120 volts and limit what is used simultaneously.
1500 watts is 12.5 amps. With two of those heaters running with lights at that distance you are using up all of the 30 amps of power you have. You probably need to check the wire coming in from time to time to see if it's getting hot.
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post #46 of 80 Old 08-15-2016, 07:44 AM
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which is it?

Quote:
Originally Posted by holtzdreher View Post
Well I had the chance to check the wire to the barn. 10-3. I was certain I purchased 8 ga wire and was so puzzled by it that I would have dug through old tax records for the wire receipt, except they were lost in a fire. I remembered that I had some extra wire stored in the back shed. I went digging and found a part of a spool of 8-3. Not enough left to run to the barn. So I did purchase 8-3, I just don't know what happened to it. Anyway, I am stuck with a 125 ft run of 10-3 to the barn. So. I will have to watch my amps draw a little closer. (In the winter, I run up to two water trough heater ats 1500 watts each.) The lights have all been changed to LEDs so that draw is minor.

So I guess i will need to rewire the connections to the motor to 120 volts and limit what is used simultaneously.
!0-3 would not make sense for such a long run when you installed it. JMO.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #47 of 80 Old 08-15-2016, 07:54 AM
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Originally Posted by Rick Christopherson View Post
Unfortunately you were misinformed, but it's not uncommon. Rebuilding motors is a mechanical occupation. They don't need any electrical background. The same is actually true for electricians. Most (but not all) have very little electrical knowledge.

This is not a new topic. I wrote Electricity in the Woodshop 20 years ago because of it. I invite you to read that, as it covers and explains all of the points you just stated. There was a time that if you Googled the word Electricity, this article was the first hit.

Because the windings are switched between either series connected or parallel connected, the voltage and amperage through each winding is the same regardless how they are configured to external configuration.
That statement won't wash that a technician that has been rewinding and repairing electric motors for more than 40 years doesn't know how electricity works in a motor.
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post #48 of 80 Old 08-15-2016, 10:15 AM
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Well I had the chance to check the wire to the barn. 10-3.
When you say 10-3, do you mean Black-White-Green(or bare copper) or do you mean Black-Red-White?
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post #49 of 80 Old 08-15-2016, 11:06 AM
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When you say 10-3, do you mean Black-White-Green(or bare copper) or do you mean Black-Red-White?
The cables you refer to are generally called 10-2/G or 10-3/G, the G refers to a bare ground wire. To an outbuilding, perhaps it's direct-burial wire, but in any case a bare copper wire isn't needed. Instead you drive a ground rod at that building and connect the ground wires from the outlets to that. And where the white wires and the green or bare wires all go to the same buss-bar in the panel of the main building, at the outbuilding the white wires are kept separate on their own bar.

If you have 10-3 that is Black-Red-White you've got 240 and a capacity of 7,200 watts. If you've got Black-White-Ground you have 120 and 3,600 watts.

By code you're supposed to de-rate motors and heating circuits to 80% of those numbers.

If you've got 240, and the saw runs 240, with no other load your voltage drop would be 1.2%, and you are fine.

If all you have is 120, and the saw will run on 120, the voltage drop will be 4.9%, the saw will run OK but you'll want to take it easy and avoid loading the motor with heavy cuts one right after the other. Keep the saw running idle for a bit between cuts.

Above assumes copper wire.
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post #50 of 80 Old 08-15-2016, 12:34 PM
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good write up brian,


additionally, notes for anyone calculating or using voltage drops.


if using the formula E = I x R for calculating the drop, the wire resistance/foot is multiplied by the total distance traveled by the current, which is out and back for both 120 volts AND 240 volts systems.


Since motors should always be kept below 5% voltage drop, large amperage loads when configured for 120 volt are typically wired with a larger wire gauge to compensate for voltage drop.
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post #51 of 80 Old 08-15-2016, 12:44 PM
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Originally Posted by Brian(J) View Post
The cables you refer to are generally called 10-2/G or 10-3/G, the G refers to a bare ground wire. To an outbuilding, perhaps it's direct-burial wire, but in any case a bare copper wire isn't needed. Instead you drive a ground rod at that building and connect the ground wires from the outlets to that. And where the white wires and the green or bare wires all go to the same buss-bar in the panel of the main building, at the outbuilding the white wires are kept separate on their own bar.

If you have 10-3 that is Black-Red-White you've got 240 and a capacity of 7,200 watts. If you've got Black-White-Ground you have 120 and 3,600 watts.

By code you're supposed to de-rate motors and heating circuits to 80% of those numbers.

If you've got 240, and the saw runs 240, with no other load your voltage drop would be 1.2%, and you are fine.

If all you have is 120, and the saw will run on 120, the voltage drop will be 4.9%, the saw will run OK but you'll want to take it easy and avoid loading the motor with heavy cuts one right after the other. Keep the saw running idle for a bit between cuts.

Above assumes copper wire.
There are several ifs, ands and buts about that ground rod. I seen people try to use and stores sell, 4 foot ground rods. These are not adequate under any conditions.

A minimum of a 10' copper rod is needed. In some soils even that is not sufficient. Where I live it is not adequate. On Eglin AFB we have even gone to the extreme of digging a 110' deep well to bury a ground place. And then the soil was salted to further increase the effectiveness.

I brazed together three 10' copper pipes and jetted them in to 30 feet deep to supplement my house's ground.

George
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post #52 of 80 Old 08-15-2016, 02:02 PM
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That statement won't wash that a technician that has been rewinding and repairing electric motors for more than 40 years doesn't know how electricity works in a motor.
So, a well known electrical engineer tells you that you are mistaken, and you want to continue arguing that your sources are reliable? Got it. You can lead a horse to water, but I stopped trying to force them to learn a long time ago. But you would be well served to pay attention and do some additional research as needed.
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post #53 of 80 Old 08-15-2016, 03:11 PM
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Not necessarily so

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That statement won't wash that a technician that has been rewinding and repairing electric motors for more than 40 years doesn't know how electricity works in a motor.

The ground crew mechanic who works on the plane, can't fly it. The computer wizard at the Best Buy can remove your virus, but can't write programming code. The auto mechanic who replaces the broken parts at the dealership can't fix/repair/rebuild them. The carpenter/house framer who builds the home can't design one.

A technician is not an engineer. Electrical theory is more complex than most can appreciate. I had a few structural engineering classes in college and when it came to calculus and differential equations a whole lot was over my head, but I squeaked by with a new appreciation for engineers. :smile3:

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 08-15-2016 at 04:19 PM.
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post #54 of 80 Old 08-15-2016, 03:50 PM
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It is also possible that from practical experience the guy that has been rewinding motors for 40 years has discovered that despite the specs given by an engineer there are other factors that come into play for a better or more reliable repair. He will not be able to prove why on paper to justify his method, he just knows it works.

Wise men speak because they have something to say; fools because they have to say something -Plato

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post #55 of 80 Old 08-15-2016, 05:33 PM
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It is also possible that from practical experience the guy that has been rewinding motors for 40 years has discovered that despite the specs given by an engineer there are other factors that come into play for a better or more reliable repair. He will not be able to prove why on paper to justify his method, he just knows it works.
Do not see what that has to do with the current subject? I have also seen just the opposite happen.

George
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post #56 of 80 Old 08-15-2016, 05:50 PM
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It is also possible that from practical experience the guy that has been rewinding motors for 40 years has discovered that despite the specs given by an engineer there are other factors that come into play for a better or more reliable repair. He will not be able to prove why on paper to justify his method, he just knows it works.
A motor technician has no idea what is behind the design of the motor. All he does is remove the existing coils of wire and replaces them with identical new coils. His two primary concerns are whether he used the same wire gauge and the exact same number of turnings per coil. It is purely a mechanical job.

But that's not even the point. According to Steve, his motor "expert" incorrectly described how a motor even functions in the first place. That is an inarguable sure sign that his "expert" doesn't have a clue as to how a motor works.

No offense to either, but it is not a point that can even be argued. It's a failure of freshman or even high school electricity, and not even close to understanding magnetic principles of motors.
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post #57 of 80 Old 08-15-2016, 06:09 PM
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I mentioned this before

For anyone who is interested in the various issues in woodworking,....electricity in the woodshop, getting square cuts, static in dust collectors, climb cutting vs normal with a router check out this site linked above in Ricks signature.

Great information: http://www.waterfront-woods.com/

Also check out the expanding round table build.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #58 of 80 Old 08-15-2016, 06:28 PM
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There are several ifs, ands and buts about that ground rod. I seen people try to use and stores sell, 4 foot ground rods. These are not adequate under any conditions.

A minimum of a 10' copper rod is needed. In some soils even that is not sufficient. Where I live it is not adequate. On Eglin AFB we have even gone to the extreme of digging a 110' deep well to bury a ground place. And then the soil was salted to further increase the effectiveness.

I brazed together three 10' copper pipes and jetted them in to 30 feet deep to supplement my house's ground.

George
Yes, there are always the details and the exceptions. In many, perhaps most parts of the US two 8' ground rods 72" apart are now required, with bare copper between them. So you get 16' of galvanized ground rod and 6' of #4 copper
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post #59 of 80 Old 08-15-2016, 06:50 PM
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It is also possible that from practical experience the guy that has been rewinding motors for 40 years has discovered that despite the specs given by an engineer there are other factors that come into play for a better or more reliable repair. He will not be able to prove why on paper to justify his method, he just knows it works.
Steve, I've seen your posts around this site and for me you've got plenty of street cred. I never get the idea you are just pasting in some info you got off the net somewhere, it feels like you've been to the rodeo quite a few times. Where I'm ignorant, like wood finishing, I would consider your counsel carefully. But I'm surprised that what a guy told you 15 years ago and that one experience has become the gospel in spite of any information to the contrary.

FrankC, your point, that practical experience may prove more accurate than some theory, great. But in my case, when I became an electrician I went to night school for three years, motor school was three months. My instructor got his training in the Navy and ended up the chief electrician on the battleship Missouri, he had some stories to tell. We built a couple different crude but working motors, and then that profession became my life's work for 15 years. Lots of problems with lots of motors. I'm pretty sure I know what was going on with Steve's motor and why getting it on a 240 circuit fixed the problem, and 120 wasn't the problem, but that's just speculation.

I think the only way to get Steve, and maybe Frank, on board is to set up two identical tablesaws side by side, 120 and 240, don't tell them which, and let them try to tell the difference. I wait for the results.
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post #60 of 80 Old 08-15-2016, 08:55 PM
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Who's the "well known electrical engineer"?

I've never heard of any of you.

Is he new?

"When I have your wounded." -- Major Charles L. Kelley, callsign "Dustoff", refusing to recognize that an LZ was too hot, moments before before being killed by a single shot, July 1, 1964.
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