Any benefit in running my bandsaw on 220 instead of 110?

[Phillip Gregory]

Please see my comments below: Your misconceptions are common but incorrect.

A very small amount of research on the Internet - even Wikipedia - will demonstrate that the US residential service is single phase.

Mike

[Look here. A quote taken from the article: "...a split single-phase is not a two-phase system."][/QUOTE]

It is not technically considered two-phase because it was generated from a single phase using one alternator winding instead of two separate windings. That's all Wikipedia said on the topic. The very tiny two-phase distribution system stemming from the late 19th century had the phases offset by 90 degrees, which was clearly different from split phase and did require different sets of motor windings to generate. Academically, a split-phase system is otherwise identical to the equipment running on it (not the distribution system before the center-tapped transformer!) as two-phase with a 180 degree offset:

split-phase-sine-wave.gif

The summation of the potential differences (absolute values) of the two sine waves does lead to a single sine wave with twice the amplitude, which is why the equipment running on 240 volts doesn't care if the 240 volts is split phase, single phase, or two phases off of a 240 V delta or wye 3-phase setup. All it cares is that between two wires there is 240 volts of potential difference. 240 volt northern Western Hemisphere split-phase is NOT the same as 240 volt one-hot-and-a-neutral most-of-the-rest-of-the-world single-phase from a wiring perspective though. One simply has to wire a 240 volt split-phase receptacle vs. a 240 volt one-hot-and-a-neutral receptacle and that difference is obvious. You wire a 240 V split phase receptacle identically to wiring two phases of 208Y three-phase (which would be offset by 120 degrees) to an identical piece of equipment such as a stove or a 280-240 volt "single phase" motor with two hots and no neutral. Rest of the world one-hot-and-a-neutral 240 V would be wired identically to North American 120 volt, 277 volt, or 347 volt with one hot and a neutral, not two hots.

The single phase part comes from the transformer primary is fed by only one generated phase from the power plant's alternator rather than drawing off two phases from the power plant, as you would with a "true" two-phase setup rather than split phase.

[Mike Henderson]

A very small amount of research on the Internet - even Wikipedia - will demonstrate that the US residential service is single phase.

Mike

[Look here. A quote taken from the article: "...a split single-phase is not a two-phase system."]

It is not technically considered two-phase because it was generated from a single phase using one alternator winding instead of two separate windings. That's all Wikipedia said on the topic. The very tiny two-phase distribution system stemming from the late 19th century had the phases offset by 90 degrees, which was clearly different from split phase and did require different sets of motor windings to generate. Academically, a split-phase system is otherwise identical to the equipment running on it (not the distribution system before the center-tapped transformer!) as two-phase with a 180 degree offset:

split-phase-sine-wave.gif

The summation of the potential differences (absolute values) of the two sine waves does lead to a single sine wave with twice the amplitude, which is why the equipment running on 240 volts doesn't care if the 240 volts is split phase, single phase, or two phases off of a 240 V delta or wye 3-phase setup. All it cares is that between two wires there is 240 volts of potential difference. 240 volt northern Western Hemisphere split-phase is NOT the same as 240 volt one-hot-and-a-neutral most-of-the-rest-of-the-world single-phase from a wiring perspective though. One simply has to wire a 240 volt split-phase receptacle vs. a 240 volt one-hot-and-a-neutral receptacle and that difference is obvious. You wire a 240 V split phase receptacle identically to wiring two phases of 208Y three-phase (which would be offset by 120 degrees) to an identical piece of equipment such as a stove or a 280-240 volt "single phase" motor with two hots and no neutral. Rest of the world one-hot-and-a-neutral 240 V would be wired identically to North American 120 volt, 277 volt, or 347 volt with one hot and a neutral, not two hots.

The single phase part comes from the transformer primary is fed by only one generated phase from the power plant's alternator rather than drawing off two phases from the power plant, as you would with a "true" two-phase setup rather than split phase.[/QUOTE]


Let me see if this will help. Imagine the neutral is completely removed. The transformer on the pole is just a 240V secondary with no center tap. So nothing in your house is 120V. You have two wires serving your home, plus a ground for safety. All of your 240V motors work just fine.

The voltage is single phase - I'm sure you can see that because the input to the transformer is single phase. The voltage is 240 V because that's what the secondary of the transformer is. Can you see that?

Now, add a center tap on the secondary of the transformer on the pole but don't do anything with it. Nothing is changed, is it? You still have 240V single phase. Can you see that?

Now, bring the center tap to the main box but don't do anything with it. Hook it up, but everything is still 240V single phase in your house. Can we agree that all of your 240V circuits are still single phase?

Now hook up a few 120V circuits to your main box. Has that changed your 240 V circuits? No, they are still single phase. You have 240V across the two wires supplying all of your 240V circuits.

We only WISH we could get two phase that easily from a single phase circuit.

There was a two phase system years ago, and I think it is still used in a few places even today. That was two phasors separated by 90 degrees. You can find a description of that two phase system on the Internet, I think on Wikipedia.

Mike

[Another example: Suppose the transformer on the pole had three taps evenly spaced, with 5 wires coming into your house. The voltages available to you would be 60V, 120V, 180V and 240V, all single phase. Surely you aren't going to try to say that that system is a 4 phase system.]

[The US residential distribution system is similar in certain ways to David Morse's idea for getting 120V off of a 240V motor - all single phase.]

[David L Morse]

Split-phase 240 volts in the US is really is two-phase.

If you look up the IEC definition of Multiphase Systems you'll find that there are no rules; you can pretty much call it whatever you want. In common usage however two phase refers to systems that have a 90° or (270°) separation between the phases.

Single phase, center tapped or not, cannot be converted to multiphase with just transformers. Two phase can be changed to three phase and vice versa with proper transformer connections.

Three phase can be implemented with center tapped transformers like single phase but that's not usually called six phase although according to the IEC you could if you wanted to.

Single phase, two phase and three phase are just labels that are conventionally used to refer to certain electrical systems. Don't get too hung up in trying to extract meaning from the names. We agree on the definitions so we can understand each other better.

[Ole Anderson]

So does anybody here actually have their EE stamp, if there is such a thing? Interesting discussion with a lot of "experts" contradicting a lot of "experts". I am a CE (with a stamp) but I am not going to jump into this discussion which would be out of my area of expertise.

[Malcolm McLeod]

So does anybody here actually have their EE stamp, ....

I do not. I am BSME, that got corrupted by the dark side many years ago (I was dragged kicking and screaming into the PLC/controls integration/SCADA world. And now love it.)

My suggestion, for powering a lamp, is based on other's electrical designs. I am familiar with the method via my involvement with site commissioning and acceptance testing of those designs. It is also how (fellow SMC-er) Mr. Baker's 230V elevator's 115V brake is actuated. The method is, in my semi-learned, wholly-unlicensed, generally-illiterate opinion - - a cheap way to do it. Did I mention cheap? Cuz' its cheap!

Apologies for re-lighting the fuse.

[Mike Henderson]

So does anybody here actually have their EE stamp, if there is such a thing? Interesting discussion with a lot of "experts" contradicting a lot of "experts". I am a CE (with a stamp) but I am not going to jump into this discussion which would be out of my area of expertise.

I don't know what EE stamp is but I'm an electrical engineer (BSEE, MBA) and spent my entire working life doing EE work. I hold a number of US patents on EE subject matter.

But more importantly, look to the logic of the arguments.

Mike

[Malcolm McLeod]

Stamp :: registered Professional Engineer

[Mike Henderson]

I am not a registered professional engineer. When you work for a large company, you don't need the PE certification. That's only needed when you hang out your shingle.

I'll just add that the vast majority of Electrical Engineers working in industry, including silicon valley, are not PEs. In my whole career, I only met a couple of EEs who had PE certification, and mostly because they had an outside business of their own.

Mike

[Malcolm McLeod]

Thought something got lost. Never mind.

[Tom Deutsch]

Nope, that's not how dual-voltage motors work. When a dual-voltage motor is connected to 120V, both windings (or groups of windings) are connected to the hot wire on the "front" end of the windings, and the neutral on the "back" end of the windings (a "parallel" wiring scheme). When connected to 240V, one hot leg of the 240V supply is connected to the front end of one winding, then the back end of that winding is connected to the front end of the second winding, then the back end of the second winding is connected to the second hot leg of the power supply (a series winding).

Yep. That's how they are wired. Not sure where I contradicted serial vs parallel (other than the "separate but equal" remark - which ignored the fact that one leg becomes the return when the other is pushing electrons.) I was trying to illustrate ... conceptually and not specifically ... for those of us (like me) who get dizzy when we read engineers' explanations of wiring diagrams. LOL. I work as a creative director in web development with software engineers, so I'm used to being told that I'm wrong when I boil stuff down. ("But you didn't exclude when a volcano explodes, therefore you are wrong!")

But I'm glad to hear that the voltage does add up when it's connected to both wires; that's why I always go for it when I have a choice. Then how can a 230v-wired motor NOT be more obviously superior to the same 115v-wired motor than this long debate suggests?

[Dan Friedrichs]

So does anybody here actually have their EE stamp, if there is such a thing? Interesting discussion with a lot of "experts" contradicting a lot of "experts". I am a CE (with a stamp) but I am not going to jump into this discussion which would be out of my area of expertise.

I do, and Mike's right

[Peter Aeschliman]

Soooo.... is there any benefit of running a bandsaw on 220 vs 110?

[Mike Henderson]

Soooo.... is there any benefit of running a bandsaw on 220 vs 110?

If the circuit is adequate, no.

Mike

[Ole Anderson]

If the circuit is adequate, no.

Mike

That much I knew...

[Peter Aeschliman]

Ha

Just messing with you guys. The conversation went about 2,000 miles over my head, so I couldn't help but dumb it down for a sec.