220v vs 110 motor

[LCHIEN]

You are right. What I said is confusing.

But if you use a clamp on volt meter on a 220V line with a motor drawing 8 amps each line will show 8 amps. Because each line is perfectly out of phase with the other at any one time only 8 amps are drawn across both lines. However, to use jschen's example slightly modified:

P = 110V * 14A = 1,540 watts Leg 1 of the 220 circuit
P = 110V * 14A = 1,540 watts Leg 2 of the 220 circuit

Taken together we can say we have two 110v circuits together drawing 28 amps.
P = 110V * 28A = 3.080 watts

Or one 220V circuit drawing 14a
P = 220V * 14A = 3,080 watts

We use the latter because as stated above with each 110V circuit being perfectly out of phase with the other at any given time only 14A is being drawn across both lines when measured at the same instant ergo, wire rated for 14A is needed. However, I contend that since we do not have 220V between a singe line and ground but have two 110V lines that each are providing 14A for a total of 28A or 3,080W. We use the calculation of 220V times 14A (which is really the same as 110V times 28A) to reach the 3,080W because if we did not electricians would never be able to figure out what size wire to use.

Therefor, in the US with 220 being really two 110V lines (we are not talking about 3 phase here) the same total amps are drawn if we measure across each line independently.

Bill
and the airplane on the conveyor will take off.

so all you've really said and I agree is that both 110 and 220V will use the same wattage (power). Where you measure those currents and how divide the current loops is beyond most peoples understanding. I see what you are trying to say but I'm an electrical engineer.

[gsmittle]

This is starting to sound like the Airplane-On-The-Conveyor-Belt discussion…

I have no dog in this fight—it just seems to me that one needs to weigh the cost and effort of running a 220 line + future benefits vs 110 right now.

g.

[woodturner]

But if you use a clamp on volt meter on a 220V line with a motor drawing 8 amps each line will show 8 amps. Because each line is perfectly out of phase with the other at any one time only 8 amps are drawn across both lines.

Umm, no.

Both lines are, by definition, in phase. The part I think you are missing is the directly of current flow - which some clamp on meters do not indicate. Electricity HAS to flow in a loop - there is an in and an out - and the current in any part of the loop IS the total current.

I think what you may be trying to say is that because the current flow is reversed, the voltage waveform is the inverse. However, to say that it is "perfectly out of phase" or even 180 degrees out of phase is really not correct. It's really in phase with a different direction of flow.

If you use an in-line ammeter, on line 1 you will see current flowing from the source (receptacle) toward the motor. On line 2, you will see current flowing from the motor to the receptacle.

You will see the same thing for the 120 VAC example. With your clamp-on meter, you would see 16A in the hot and 16A in the neutral. So, by your explanation, you would say the 120 circuit is drawing 32A. If that is the case, why is the breaker not tripping?

The answer is what all us engineers (like LCHIEN, I am an EE - a licensed professional engineer) and others have posted - the current in one leg of the circuit IS the total current. There HAS to be a loop for the circuit to work.

Taken together we can say we have two 110v circuits together drawing 28 amps.
P = 110V * 28A = 3.080 watts

No, that is NOT correct. It is one 220V circuit drawing 14A, NOT two 110 VAC circuits drawing 28A. If you measure the voltage between each wire and ground, you will usually not see 110VAC (one is usually higher - 170V and 50V, something like that - but the actual voltages will vary), but you WILL see 220V between the two wires.


The primary advantage of higher voltage is that the current required to achieve a given power level is lower. Thus smaller wire can be used without excessive voltage drop, since the voltage drop in the wire is proportional to current. That's why the power company sends higher voltage, lower current biphase or three phase power to your pole, then transforms it down to residential voltages.

BTW, three phase is available in many neighborhoods, particularly older ones. Might be worth checking.

Also, three phase motors will run on single phase or biphase (220V), but will not be able to develop full power. Could be useful for testing, if nothing else.

[woodturner]

This is starting to sound like the Airplane-On-The-Conveyor-Belt discussion…

One difference, though is that the "questions" in this thread were never really questions - there are standard, well defined and researched answers.

In the airplane discussion, there are not standard answers and defined specifications, so there are not reliable references to eliminate any question. Thus we all have to think about it and form a conclusion.

[cabinetman]

For all practical purposes, the power and hence cost of operating the a 110/120V motor or a 220/240V motor will be the same, for the same work.

The 110 will take twice the amps of the 220V motor to do the same work. But the power is the same.

If nothing else is on the line then you have no problem and operation is the same.

I can appreciate the responses from the "engineers" and their evaluation, but as it was put for all of the "regular" people here on this woodworking forum, some formulas may answer a question, but not afford an understanding in common terms.

The question of efficiency, with respect to cost, not work... a given motor that is 110V/220V capable, running for 5 minutes under no load in each voltage arrangement, are you saying will cost the same in electrical draw?
.

[woodturner]

a given motor that is 110V/220V capable, running for 5 minutes under no load in each voltage arrangement, are you saying will cost the same in electrical draw?
.

That's correct. Electricity is sold in kilowatt-hours, which is kilowatts consumed per unit time.

So, assuming this is the OPs 1.5 HP motor, it would draw around 15A at 110 VAC or 7.5A at 220VAC - but 1.65 KW in both cases. So, if you run it for an hour, the utility will charge you for 1.65 kWh - regardless of the operating voltage.

[cabinetman]

For all practical purposes, the power and hence cost of operating the a 110/120V motor or a 220/240V motor will be the same, for the same work.

The 110 will take twice the amps of the 220V motor to do the same work. But the power is the same.

If nothing else is on the line then you have no problem and operation is the same.

Lets say there is a 110V and a 220V receptacle on the wall and each is a dedicated source with nothing else being run off of them, and a 110V/220V motor is configured to run off of one or the other, is there any reason to run it on one versus the other. IOW is a motor more efficient running on one or the other, since the cost is the same?
.

[LCHIEN]

Lets say there is a 110V and a 220V receptacle on the wall and each is a dedicated source with nothing else being run off of them, and a 110V/220V motor is configured to run off of one or the other, is there any reason to run it on one versus the other. IOW is a motor more efficient running on one or the other, since the cost is the same?
.

Not really that will be noticable.
The 110/220 motors have two windnigs, they are paralleled for 110 and placed in series for 220V. So the current in each winding will be the same if there is 110 at the motor input set up for 110 and 220V at the input when set up for 220V. therefore the motor performance will be the same since the effort of the windings is mechanically summed

technically, assuming that we have say 12 gauge wire to each socket, there will be more loss from the breaker box to the socket with the higher current at 110V. But only around 2% which will be unnoticable to most anybody if you read below.

Lets assume 100 feet breaker to the socket. 200 feet round trip (two wires) 12 ga. wire is .16 ohms per 100 feet, so .32 ohms.
1.5 HP machine fully loaded drawing about 15A at 115 or 7.5A at 230V (nominal voltages)
So the voltage drop with 115 will be 4.8 and the voltage drop at 230 will be 2.4 volts. or a difference of 2.4 volts.
That's about 2% less voltage. Since the machine is rated to work over a voltage range of at least 110 to 120 it'll actually stand a drop from 115 to 110.2 with no issues.
Your motor won't start to saturate current until below about 105- volts typically so there will be no performance loss. You start having motor issues when you load it and the current tries to increase to compensate for lower votlage and the winding current rating is exceeded - since the magnetic forces can no longer increase with current at this point - the excess current becomes heat and that's why motors burn up in this condition.
Certainly 2% power loss will be unnoticable by any person.

[cabinetman]

Not really that will be noticable.
The 110/220 motors have two windnigs, they are paralleled for 110 and placed in series for 220V. So the current in each winding will be the same if there is 110 at the motor input set up for 110 and 220V at the input when set up for 220V. therefore the motor performance will be the same since the effort of the windings is mechanically summed

technically, assuming that we have say 12 gauge wire to each socket, there will be more loss from the breaker box to the socket with the higher current at 110V. But only around 2% which will be unnoticable to most anybody if you read below.

Lets assume 100 feet breaker to the socket. 200 feet round trip (two wires) 12 ga. wire is .16 ohms per 100 feet, so .32 ohms.
1.5 HP machine fully loaded drawing about 15A at 115 or 7.5A at 230V (nominal voltages)
So the voltage drop with 115 will be 4.8 and the voltage drop at 230 will be 2.4 volts. or a difference of 2.4 volts.
That's about 2% less voltage. Since the machine is rated to work over a voltage range of at least 110 to 120 it'll actually stand a drop from 115 to 110.2 with no issues.
Your motor won't start to saturate current until below about 105- volts typically so there will be no performance loss. You start having motor issues when you load it and the current tries to increase to compensate for lower votlage and the winding current rating is exceeded - since the magnetic forces can no longer increase with current at this point - the excess current becomes heat and that's why motors burn up in this condition.
Certainly 2% power loss will be unnoticable by any person.

So, what are you trying to say? If there is a choice...run it 220V?
.

[woodturner]

So, what are you trying to say? If there is a choice...run it 220V?
.

There is a slight technical advantage to running a motor at 220 VAC, but most people in most situations won't notice a difference.

If the motor is 2 HP or larger, definitely run it on 220 VAC.

If the wire run from the service panel to the motor is "long", you may see some benefit from the lower voltage drop if you run it at 220 VAC. For most runs in most houses or shops, though, the difference would be negligible.

[woodturner]

IOW is a motor more efficient running on one or the other, since the cost is the same?
.

Efficiency is a function of the motor construction, not the wiring.

[master53yoda]

In our environment with properly sized wire there is no difference between running it on 110 VAC then running it on 220 vac. in all reality you can run any size motor on any voltage if the wire is big enough. You could run a 10 HP motor on 110 Volts but you would need to run #1/0 copper wire to it and have it on a 120 amp breaker but it would work just fine.

I have worked with many high HP motors up to 2500 HP on 4160 VAC 3 phase.

the reason for raising the voltage to the motor as high as possible is to use as small a wire as possible.

residential doesn't intend on running anything higher then 20 amp circuits at 110 Volts so that limits the true motor HP to 1.7 HP on a 110 volt circuit. Any larger motor and you go to 220 volt and can then go to 3.5 hp on a 20 amp 220 vac circuit. A 5 hp requires a 30 amp circuit minimum and for a long run (over 100ft from the breaker) you need to go to #8 wire instead of #10.

In summary there is no reason to go to 220 VAC on a 1.5 hp or smaller motor.

[LCHIEN]

I can appreciate the responses from the "engineers" and their evaluation, but as it was put for all of the "regular" people here on this woodworking forum, some formulas may answer a question, but not afford an understanding in common terms.

The question of efficiency, with respect to cost, not work... a given motor that is 110V/220V capable, running for 5 minutes under no load in each voltage arrangement, are you saying will cost the same in electrical draw?
.

I wrote
"the power and hence cost of operating the a 110/120V motor or a 220/240V motor will be the same, for the same work."

Does that not answer your question? No load is no load, just the weight of the armature and the friction of the belts and bearings, the same for either voltage confiuration.


Woodturners answers in the prior couple of posts are all correct, I agree.

All things being equal, I'd use the 220V outlet if it were available, its gets you a percent or two advantage in power savings, you would not be able to discern it though*. If there were the slightest reason not to use the 220V outlet, say you needed to move teh tool to be closer and avoid an extension cord, or if I needed the 220V outlet for a 3 HP tool, then I'd surely run the 1.5 HP tool on 110/120 rather than run a new 220V line for it or even spend the money for an extension cord or even expend the energy to move it.

*Assume you used a tool 1.5HP tool at an average 50% load, say 8 Amps, 110V for 125 hours a year (that's a lot - 20 minutes of actual on time every day) you would use a 100 KWH of energy - that would cost you about $15 a year to run. Saving 2% of that would be about 30 cents a year. like i said, barely discernable.

[master53yoda]

I wrote


*Assume you used a tool 1.5HP tool at an average 50% load, say 8 Amps for 125 hours a year (that's a lot - 20 minutes of actual on time every day) you would use a KW of power - that would cost you about 15 cents a year to run. Saving 2% of that would be about 0.3 cents a year. like i said, barely discernible.

sorry but your off one decimal point. It should about $15.00 per year and savings of about .30 pennies still totally negligible. It would take about 40 years to get back the cost of the breakers not counting the difference in motor cost.

[LCHIEN]

sorry but your off one decimal point. It should about $15.00 per year and savings of about .30 pennies still totally negligible. It would take about 40 years to get back the cost of the breakers not counting the difference in motor cost.

You caught me. you're absolutely right - not just one decimal point but two. I forgot to multiply by the voltage! I thought that seemed awful low but i failed to catch my error. I wiill correct the post!