Odd plug on table saw - Page 2 - Woodworking Talk - Woodworkers Forum
Old 08-08-2016, 10:13 AM
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Originally Posted by Steve Neul View Post
Nothing to absorb, there are two individual fields on a duo-voltage motor. You have the main winding and the auxiliary winding. When one is positive the other is negative when running at 220v. On 110v only the main winding is used for power.
Wrong Steve.

All windings are active regardless of the voltage, there is not a primary, and auxillary. All windings run at 120V regardless of the supply.

If only half are active, how do you explain the current difference?

It should be the same, and the HP should be less running on 120V if only half are active.

So yes, there is something to absorb, and you still haven't...

Explanation - The windings of a single-phase dual voltage 120V/240V motor are 120V rated windings. They must be put in parallel on 120 so that they will be connected at their rated voltage. Likewise, if put in series on a 240V supply, the 240V divides across the two equal resistance windings, so 1/2 of the 240V (120V) is applied across each winding.

If you put the windings in series on 120V, you would only receive 60V on each winding, which would not be enough to provide the proper magnetizing effect to develop turning torque.

If you put the windings in parallel on 240V, you would be putting the full 240V on each 120V rated winding, and you would burn the windings up.

http://www.thewoodnerd.com/articles/motorRewire.html

Last edited by shoot summ; 08-08-2016 at 10:36 AM.
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Old 08-08-2016, 10:35 AM
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>>If the motor was on a bench not hooked up to anything the amperage would be the same either 110v or 220.

aye, and there's the rub.
"the same amperage" at 110v is "the same wattage"
"the same amperage" at 220v is "twice the same wattage"
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Old 08-08-2016, 10:42 AM
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Originally Posted by TomCT2 View Post
I'm curious as to why it cost less to run things on 240/220 volts.

I pay by kilowatts; watts = volts * amps.

240 motors have more starting torque/etc - but in the end it takes a certain amount of power to saw a board -
whether it's 3 amps @ 240 volts or 6 amps @ 110 volts seems to matter very little except for a possible slight difference in power factors.
other factors - size of wires=pounds of copper needed for more amps, line loss, etc apply - but outside of factory size shops, how much difference does this really make?
Hi Tom,
You may be replying to my post, I meant the cost to install the circuit and not the cost to operate the tool. And you are correct it doesn't make a lot of difference really.
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Old 08-08-2016, 10:45 AM
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Quote:
Originally Posted by TomCT2 View Post
>>If the motor was on a bench not hooked up to anything the amperage would be the same either 110v or 220.

aye, and there's the rub.
"the same amperage" at 110v is "the same wattage"
"the same amperage" at 220v is "twice the same wattage"
Red is an untrue statement, not sure where you got it.

A 1HP motor draws [email protected], and [email protected] The wattage calculates to be the same, as does the HP.

P(W) = PF × I(A) × V(V)

Last edited by shoot summ; 08-08-2016 at 10:52 AM.
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Old 08-08-2016, 12:10 PM
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Originally Posted by holtzdreher View Post

I laid wires to have 240 volts to the barn's sub panel, but the electrician that hooked things up did something that resulted in only 120 volts to the barn. The barn is 125 feet from the main panel. I remember the underground 4 wire was gosh awful expensive, 8 ga perhaps.
4 wire absolutely should have resulted in 240 volts being available. H-H-N-G. it may be as simple as adding a two pole circuit breaker in the sub-panel. or, both hots were not connected to a 2 pole cb in the main??
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Old 08-08-2016, 03:47 PM
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where I got it?

quoted from a preceding post.....
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Old 08-08-2016, 03:52 PM
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Originally Posted by Brian(J) View Post
Hi Tom,
You may be replying to my post, I meant the cost to install the circuit and not the cost to operate the tool. And you are correct it doesn't make a lot of difference really.
not really a reply to any specific post - just the on-going "theory" that 240v stuff is cheaper to run. this thread, multiple other threads, etc etc.

it's an old wives rumor that will not short out.

I personally don't pay per volts or per amps; I supposed some utilities might charge somehow other than watts - or perhaps we're missing a magic cold fusion 220v sub-panel. but power is power and it's quite normally sold in watts.
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Old 08-08-2016, 05:02 PM
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Originally Posted by Steve Neul View Post
Nothing to absorb, there are two individual fields on a duo-voltage motor. You have the main winding and the auxiliary winding. When one is positive the other is negative when running at 220v. On 110v only the main winding is used for power.
I've never heard of main/auxiliary windings, although some might refer to a starting winding as an "auxiliary" winding, as it drops out of operation when the motor reaches a certain speed. Dual voltage motors have 2 separate windings, but both are used. They're in series for 220 operation, parallel for 110.
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Old 08-08-2016, 06:04 PM
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Quote:
Originally Posted by TimPa View Post
4 wire absolutely should have resulted in 240 volts being available. H-H-N-G. it may be as simple as adding a two pole circuit breaker in the sub-panel. or, both hots were not connected to a 2 pole cb in the main??
Tim,
Exactly right. If the OP will tell us-
1. the number of wires
2. the size of each wire
3. Copper or Aluminum
it would help develop a solution. And it might be an easy one.
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Old 08-08-2016, 07:33 PM
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To the OP, would be good to get some background on the saw if you can. Both 6-15 and 6-30 are pretty common in IT, if the person had access to surplus they might have used them in a pinch instead of the correct plug/recep. At this point I wouldn't assume anything on a used piece of equipment you haven't seen, or heard run.
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Old 08-11-2016, 09:28 AM Thread Starter
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I had a look at the motor this am. It is a Dayton, 3450 rpm. I had a wiring diagram for both "low" voltage and "high" voltage.

Seems for now it would be easier to rewire for 120 volts.
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Old 08-11-2016, 09:51 AM
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easier?

Quote:
Originally Posted by holtzdreher View Post
I had a look at the motor this am. It is a Dayton, 3450 rpm. I had a wiring diagram for both "low" voltage and "high" voltage.

Seems for now it would be easier to rewire for 120 volts.

Are you saying that it is currently wired for 240 volts? so "rewiring" it for 120 volts is easier.... than what? ... new running a 240 line? Cheaper for certain, but you must still have large enough wires for it to run efficiently on 120 volts I.E, no. 12/12 GA.

If you plan to do much more woodworking it would pay to get a 240 volt working line to the barn and since the wires are already there, it should be a simple fix.

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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Old 08-11-2016, 03:17 PM
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Quote:
Originally Posted by holtzdreher View Post
I had a look at the motor this am. It is a Dayton, 3450 rpm. I had a wiring diagram for both "low" voltage and "high" voltage.

Seems for now it would be easier to rewire for 120 volts.
Why not "for now", if you are happy with the performance then that is the end of it, if not at least you can cut some wood in the meantime.

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

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Old 08-11-2016, 06:38 PM Thread Starter
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I should have corrected the statement to It had a diagram for low and high voltage operation. I am building a new shop about this time next year and it will have a subpanel supplied with 240. For the time being, I have a corner of a pole barn to work in and only two circuits available. Trying to limit the loads. After all. I can only run one machine at a time. add lights and a fan and I am done. The new shop will hopefully have better facilities.
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Old 08-11-2016, 08:51 PM
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Originally Posted by holtzdreher View Post
Again, the saw manual warns against wiring for 240 volts, however, I do not know if it is the original motor. The manual warns against using motors that are the wrong rpm, so it looks like I have quite a bit more investigation to do. (And here I thought I would just have to replace the blade)

My shop is currently split between the pump house and the barn. I laid wires to have 240 volts to the barn's sub panel, but the electrician that hooked things up did something that resulted in only 120 volts to the barn. The barn is 125 feet from the main panel. I remember the underground 4 wire was gosh awful expensive, 8 ga perhaps. The pump house has 240 volt service but is cramped at only 8 x 13 ft. so when I am done investigaing the motor, I may have to switch the saw to the pump house.

When I have the motor figured out, I suppose it is time to correct the problem with the wiring to the barn as well.

and all I wanted to do was cut some wood!
33 posts later and I still don't know if the motor is wired for 120 volts or 240 volts and why the 4 wire run to the barn can't be "corrected" so you have 240 volts out there. If you intend to do any serious woodworking you will want the 240 volts for 3 HP motor and larger.
A 3 HP motor will just not work on 120 volts. I have five 3 HP and larger motors all run on 240 volts.

Why can't you check the motor wiring diagram to see how it is wired, never mind the plug on end. You don't have a receptacle for that plug anyway, so which ever way you want to run it, you need a different plug.

Enough talk, just wire it up and "cut some wood" ..... :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)
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Old 08-13-2016, 05:26 AM
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Quote:
Originally Posted by Steve Neul View Post
Nothing to absorb, there are two individual fields on a duo-voltage motor. You have the main winding and the auxiliary winding. When one is positive the other is negative when running at 220v. On 110v only the main winding is used for power.
I am sorry Steve, but you are incorrect on this one, as was pointed out by another member. The internal windings on a dual voltage motor are either in parallel or series, and that is the only reason why there is a difference in the current when the motor is reconfigured. The individual windings neither know nor care which way they are configured. They always see the same 120-volts internally.

Within the motor, there is no change in power, nor heat, nor energy savings, nor dollar savings. It all boils down to what is easiest to supply within the building.

Back to the original poster, yes, your description suggests a NEMA 6-15 plug. You have a choice of either running a new 240-volt circuit to the saw, or reconfiguring the motor for an existing 120-volt circuit. The choice should be made on which is the easier method for getting the motor powered.
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Old 08-13-2016, 05:52 AM
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Originally Posted by Rick Christopherson View Post
I am sorry Steve, but you are incorrect on this one, as was pointed out by another member. The internal windings on a dual voltage motor are either in parallel or series, and that is the only reason why there is a difference in the current when the motor is reconfigured. The individual windings neither know nor care which way they are configured. They always see the same 120-volts internally.

Within the motor, there is no change in power, nor heat, nor energy savings, nor dollar savings. It all boils down to what is easiest to supply within the building.

Back to the original poster, yes, your description suggests a NEMA 6-15 plug. You have a choice of either running a new 240-volt circuit to the saw, or reconfiguring the motor for an existing 120-volt circuit. The choice should be made on which is the easier method for getting the motor powered.
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.
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Old 08-13-2016, 07:24 AM
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what size motor?

Quote:
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.
I've seen motors under 1 or 1.5 HP and 2 HP that have dual voltage wiring diagrams, but none of my 3 HP motors, if I recall correctly, will run on 120 V. They are all factory wired to run on 240 v. only, so this discussion is not applicable to a 3 HP motor.

I had a 2 HP Baldor motor on my old Craftsman 10" table saw wired to 240 volts years ago. It would rip anything I ran on it easily, barely even slowing down. I parted out the saw, but still have the motor. :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; 08-13-2016 at 07:46 AM.
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Old 08-13-2016, 08:49 AM
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Originally Posted by woodnthings View Post
I've seen motors under 1 or 1.5 HP and 2 HP that have dual voltage wiring diagrams, but none of my 3 HP motors, if I recall correctly, will run on 120 V. They are all factory wired to run on 240 v. only, so this discussion is not applicable to a 3 HP motor.

I had a 2 HP Baldor motor on my old Craftsman 10" table saw wired to 240 volts years ago. It would rip anything I ran on it easily, barely even slowing down. I parted out the saw, but still have the motor. :smile3:
I figure they make a dual voltage motor so if a person can't or is unwilling to wire to to 240 can opt to use lesser power at 120v. If the voltage made no difference then they could make the motor cheaper by building it a single voltage 120v motor. As far as I'm concerned a 120/240 volt motor is designed and intended to be operated at 240 volts.
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Old 08-13-2016, 10:52 AM
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1 hp = 745.7 watts X times 110 volts = 745.7 watts X = 6.799 amps

2 hp = 1491.4 watts X times 220 volts = 1491.4 watts X = 6.799 amps

X times 110 volts = 1491.4 watts X = 13.558 amps

3 hp = 2237.1 watts X times 220 volts = 2237.1 watts X = 10.168 amps

X times 110 volts = 2237.1 watts X = 20.337 amps

You get slightly different figures if you use 120 volts and 240 volts for your equations.

Regardless, a 2hp motor or any hp motor used the same number of watts whether it is wired for 110 or 220 volts. That 2hp is 2 hp is 2 hp the world over.

As you can see for the 3 hp motor the current just gets too high to run on 110 volts. The cost of the larger wiring required for that hp and larger just prohibits using the lower voltage motor. That is why industrial motors are always run at 220 or higher voltages, not because of any gains in efficiency in the motor itself.

Then you bring in the phase of the power and the explanation gets more complicated.

George
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