Cabinet saw or Dewalt hybrid????

[Kelly C. Hanna]

You're right Jim, they sure are....alarming to say the least....

[Steve Clardy]

Not so. You are using the same total amperage...it's just split over two legs. And since you are also consuming the same number of watts (what you pay for)...the bill will be identical. 3-phase is the same way. A watt still costs you the same no matter how you consume it.

I'll have to argue that. Sure. Pulling same amps, but less load on motor reduces electrical usage.
Tell me why my 5-hp converter, running a 1 1/2hp 3-phase collector, AND a hydraulic lathe with a 3hp and a 2hp motor, 6 1/2 hp combined, pulls less watts on the meter than my new 4hp single phase collector?

[Kelly C. Hanna]

I'll have to argue that. Sure. Pulling same amps, but less load on motor reduces electrical usage.

Think of it this way Steve...you have two hot leads now instead of one...instead of the 18 amps our 1023s would draw if they could run on 110, we are now drawing 9 out of each lead. The total voltage is the same, just spread out over two leads (kinda like two plugs) and that's why the stall is less likely.

[mike lucas]

Guys, it is all about torque! And on 220 the same motor will run much more efficient. I have converted probably 100 motors over that were dual voltage. And I have yet to see one perform the same. Matter fact many of them seam like a different motor all together.

For those of you that have dual voltage motors and have never run one on 220v. You need to have it converted too 220. You will be amazed.

The torque on 220 is about twice that of 115. I was an electrician for several years on the side. And I know I have converted 100 motors for others.

Other then torque, I do not know if there are any benefits to running 220. I have heard some experts claim that it will cut your electric bill. But I do not understand how that would be, unless running more efficient would do it.

[John Weber]

I was referring to the cost to wire the feed circuit is cheaper for a 220v line then a larger 120v line. Not much for an average home owner with a hobby shop, but if you are building homes or commerical buildings the savings can add up.

John

[Chris Padilla]

Guys, it is all about torque! And on 220 the same motor will run much more efficient. I have converted probably 100 motors over that were dual voltage. And I have yet to see one perform the same. Matter fact many of them seam like a different motor all together.

For those of you that have dual voltage motors and have never run one on 220v. You need to have it converted too 220. You will be amazed.

The torque on 220 is about twice that of 115. I was an electrician for several years on the side. And I know I have converted 100 motors for others.

Other then torque, I do not know if there are any benefits to running 220. I have heard some experts claim that it will cut your electric bill. But I do not understand how that would be, unless running more efficient would do it.

Mike,

Power and Torque are (for this discussion) practically the same thing. Torque, for motors, is an angular measurement usually in foot-pounds or Newton-meters. Power is then foot-pounds/second or Newton-meter/s or J/s or W. So power is a force measured over time whereas torque is a force times distance. I do not see how you can simply say the torque is doubled when switching line voltages. Do you have more info on this...some web page or something?

[Chris Padilla]

Think of it this way Steve...you have two hot leads now instead of one...instead of the 18 amps our 1023s would draw if they could run on 110, we are now drawing 9 out of each lead. The total voltage is the same, just spread out over two leads (kinda like two plugs) and that's why the stall is less likely.

Correct, Kelly, but they are also 180 degrees out of phase with each other. If you were to run the white neutral into the 240 V circuit (just for fun) and you put an ammeter on it, it would read zero current flow.

Folks, think about how power companies send energy or power to our homes. How do they do it? They do it at VERY high voltages...like 500,000 V. Why? They run at very high voltages so that current can be minimized and wire sized can be minimized and money saved from running thinner lines over thicker lines. We all have step-down transformers to get the familiar 240/120V line voltage in our homes.

I think this anaology can be applied to our motors, too, as others have already basically done. You will run less current draw down your wires in a 240 V mode vs. 120 V mode for the same power draw. This means less stress on the wires feeding your load (motor) and could also mean running smaller wires to save money. I still don't think the motor itself cares one way or the other...still looking for that succinct explanation to Mr. Lucas' argument above.

[Dennis McDonaugh]

When a motor can run on 220 or 110 it has split windings. The windings are either connected in parallel for 120 volt operation, or in series for 240 volt operation. The individual windings never see more than 120 volts. Since the voltage across the windings does not change, the power output stays the same.

A motor running on 110 pulls double the amps of a motor on 220. Put that motor under load and the amperage draw will increase causing the wires heat. When the wires heat up, their resistance increases and the motor may not be able to pull enough amps to continue spinning. This should only be a problem if the circuits inside the wall are not sized for the tool you are using.

BTW, the math for computing wattage and torque doesn't support a 220 motor having double the torque of a 110 motor.

[Donnie Raines]

I dont know....

My 16 inch Bandsaw would stall almost everytime when wired 110(when resawing). Wired it to 220 and never had a problem again......

[Kelly C. Hanna]

I can't see how the torque is changed when the wiring is changed to 220. I read somewhere that someone thought start up torque was increased, but no one has ever proved it with an article. According to those who are in the know there's no power increase, just a different way of wiring to reduce the amp draw and prevent stalling.

[Chris Padilla]

Here is what I came up with and let me use an example. Keep in mind I don't know dilly about motors but here goes:

Let's assume a ~2 hp max output motor. That is about a 1.5 kW motor converting over to the metric system.

Wire it for 120 Vac. At max current draw, you are looking at 12.5 A.
Wire it for 240 Vac. At max current draw, you are looking at 6.25 A.

Either way you look at it, the motor will provide ~2 hp or 1.5 kW of power for you. Let ignore power factor and efficiency just for the moment along with winding loss, etc.

Clearly, less current flow will mean less heating up of the motor. For the sake of argument, let's say that twice the current flow means twice the heat or temperature rise. (I could be WAY off with that assumption but suffice it to say that doubling the current in a wire will make the wire hotter)

Motors can be made with thermal shutdown switches so it is safe to assume, from this example, that a 120 Vac-wired motor running at full load will get hotter than a 240 Vac-wired motor running at the same full load. Keep in mind they are still both delivering the same power.

I'm theorizing that as the 120 Vac-wired motor gets hotter, either its efficiency comes down and/or some thermal protection begins to kick-in. This will happen sooner on the 120 Vac-wired motor than on the 240 Vac-wired motor even though they are both, just before shut-down/weakening (lower effiiciency due to heat), delivering the same power.

I further say that it is quite possible to do this when we are cutting/milling our favorite woods and we are taxing the motor quite a bit to keep the blade moving and cutting.

How's that?

[Kelly C. Hanna]

Sounds right to me Chris!

[Ian MacDonald]

Hi Guys,

Maybe this can add a little to the conversation.

If I recall correctly from my college days...

During motor startup the instantaneous current draw is much higher than the full load current draw. In fact it can be many times the full load current. It's this instantaneous current draw that causes the large voltage drop during startup. (For you EE types, consider what happens went you energize an inductor/coil.)

This effect manifests itself as a slower acceleration to full motor speed. On a 220V wired motor, the voltage drop during startup will be half that of the 110V motor and as a result will reach full running speed more quickly. I believe this effect also comes into play when a motor is heavily loaded; the 220V motor will recover more quickly after the load is reduced than the 110V motor.

Cheers,

-- Ian

[mike lucas]

Mike,

Power and Torque are (for this discussion) practically the same thing. Torque, for motors, is an angular measurement usually in foot-pounds or Newton-meters. Power is then foot-pounds/second or Newton-meter/s or J/s or W. So power is a force measured over time whereas torque is a force times distance. I do not see how you can simply say the torque is doubled when switching line voltages. Do you have more info on this...some web page or something?

Lets say you are correct for a moment here, If torque is indeed what you stated, Then what do we do with all of the Torque wrenches? (Toss them in the trash?) If torque is a force times distance, and a torque wrench can apply 1000 ft lb without moving, then your theroy is no good. Sorry! But I have to completely disagree with you. Toqrue is an applied force, and has nothing to do with distance, or rpm.
And yes the 220v does indeed have twice the force as 110, so it is safe too say that it would have twice the torque. You can double the torque without effecting the horsepower. And the other way around is not possible.

Chris, I am not trying to be a di(k with you, some times I have a hard time explaining things, and the internet makes it even worse.

Think of it this way;
Torque gets things moving, and horsepower keeps it moving. You can have torque without hosepower, but you can not have horsepower without torque.

[Dennis McDonaugh]

Mike, your assertation is not supported by fact. Look in any physics text book and you'll find that torque is defined as a twisting motion (as in rotation) and measured as force times distance.

I don't understand your comment about throwing away the torque wrench. A torque wrench simply indicates how much force (torque) you've applied at the end of the wrench at a given instant in time.

Power is measured as force times distance moved over a period of time. Motors with different hp ratings can move the same mass, it just takes the smaller hp motor longer to move the mass.

Check out any book on motors, there is no evidence to support your claim of a motor operating on 240 volts having double the HP as the same motor operating on 120 volts. You can say it does, but that doesn't make it so. You simply can't provide any evidence to backup your claim.

power = voltage times amps

240 volts X 10 amps = 2400 watts
120 volts X 20 amps = 2400 watts

The power is the same for both motors

You also need to watch your language on this forum.