3 phase and single phase, whats better
kenney66
| Posted in Power Tools and Machinery on
Recently i purchased a 8″inch jointer. The jointer came wired for 220 3 phase with a different type plug than on smaller machines. Hopefully you know what I am trying to describe. So I am having a 220 outlet installed near the jointer so I can use it. The reason for this message is i am wondering what the difference between 3 phase and single phase is. Does one run the machine better than the other? Please help
Replies
the difference between 3 phase and single phase is.. MONEY...
I sure hope you have 3 Phase where you are. If you don't, I'd send it back or get a new single phase machine. Gets kind of expensive if you don't have 3 phase already.. If you don't have 3 phase call some local electrical contractor for a bid..
Sorry but I did that ONCE..
Its more a matter what is available (for a resonable cost) and what your needs are. You can convert to 3 phase and many do but the advantage becomes less the more you spend on converters or to have it run to your shop. Lots of "cheaper" 3 phase equipment out there if you do get set-up.
Kenny.. the primary difference is power; you can only push so many amps into a single phase motor before it can't take no more and going to a bigger single phase doesn't make much difference. That's where three phase takes over; if you need massive amounts of power and unstoppable torque, the only way to go is three phase.
Efficiency wise, you get more bang for yer buck with three phase too; because they run at a higher voltage, they draw comparativly less current making them slightly cheaper to run. In addition, their nature makes them more efficient in how they use the power.
That said, to really see the difference between the two, you need to be looking at a fair sized machine and using it under commercial or industrial conditions; an 8" planer is well within the capabilities of a modest sized single phase motor, and probably better suited to your purposes; if it's not already nstalled, three phase can cost a small fortune to install, requiring it's own breaker panel and outlets.
Mike Wallace
Stay safe....Have fun
You don't have 3-phase power in your house. It is probably not available in your neighborhood even if you re-wired all the way out to the street. If you're using this jointer at home, the cheapest thing for you to do is exchange the motor for a single phase one. You can get a converter, but it will be very inefficient (will waste a lot of electricity.) You'd be better putting that same current into a bigger single phase motor.
They are different ways to transmit alternating current.
In single phase, the voltage alternates between a single pair of wires (hot and neutral). The alternating current creates an alternating magnetic field. If a motor's rotor is spinning, the spinning distorts the magnetic field and causes the field to spin as well. The spinning magnetic field drags the rotor around with it, thus the motor turns.
Motion of the rotor is necessary to drag the field to one side or the other to start the motor spinning, otherwise, it just sits there and hums. To get it started, the shaft can be spun in either direction by hand, then, once the distortion begins, it continues on its own. A capacitor can distort the current and electronically "drag" the magnetic field to one side, thus single phase motors use a capacitor to kick them around. If the capacitor fails, the motor would only start if it were manually spun after power was turned on.
In three phase, there are three separate currents, carried between three hot wires. Say you call each wire A, B, and C. There is current between A & B, between B & C, and between C & A. They all peak at different times all equally spaced 1/180th of a second apart. First, the AB current peaks, then the BC, then the CA. If you wind a motor so the three phases magnetize separate windings arranged around the rotor, as each successive phase peaks it drags the rotor around in that direction. The motor spins nearly in time with the spin of the phase currents around the coils.
The advantages of three phases are smoothness and economy. If you imagine a game of theather ball with three players instead of one, that's how it is with three kicks spinning the rotor around vs. one. It also allows you to get power from the current with less loss, so you get more horsepower out for the power you put in. Motors can be made smaller, lighter, and cheaper to deliver the same power with three phase. And they have inherent direction -- no capacitor. You wire the phases either clockwise or counterclockwise when you hook up the motor, thereby determining the direction. It will start without a spin. And, you can change the direction by throwing a switch which criss-crosses the wires, which you can't do with single phase, because direction is determined by the capacitor.
So, larger motors are three phase because of these advantages.
Ok next question, The delta DJ-20 is what i purchased. IT came with a plug that has its prongs running the opposite direction as a normal plug. Can i just install a 220 outlet and be ok? Or is there more to the story? The manual is kind of confusing to me. What i really am looking for is how not to @#$%$ up the machine?
thanks again.
I don't know. The plugs are intentionally designed so you cannot plug a device into the wrong voltage and phase. And you must not try to get around this by installing the wrong outlet.
The surest way to proceed is to check the nameplate on the motor itself and find out what voltage it runs on and whether it's single phase or three phase. There's no way of telling what motor might be on the machine without looking at it. Then check with an electrical supply house to see if the plug you have agrees with the motor nameplate. (They have charts of plugs and outlets.) If it does, then you can install a corresponding outlet.
If the motor is three phase and you are in a home, there is no way to wire up single phase to give you three phase power. You'll either have to by a phase converter or a new motor. If your motor is 220 volt single phase, all you have to do is intall the correct outlet for the motor on a 220 volt circuit.
Kenny.. forgive me, I'm on the wrong side of the pond to be familiar with Delta machinery... this is a jointer??
If I'm right, I seriously doubt that it'llbe a three phase motor; the max load just doesn't justify that kinda motor.. I suspect that it'll be a 220v single phase motor. Either way, as already said, the rating plate that's attached to the motor will tell you for sure.. for the record, three phase plugs should have either 4 or 5 pins, single phase will only ever have 3...Mike Wallace
Stay safe....Have fun
Mike, I appreciate your comments. This woodworking stuff can get overwhelming at times. There are so many things to learn. My first hobby has been golf. IT took me a while to get good at that and I figure the same can be said for working with wood.
I have learned a lot from reading these forums and I want to say thanks to all of the people like you who that take time to help a stranger out.
Kenney
No worries Kenny... I've been at this for over 4 years now, and I'm still at the steep end of the learning curve. I've found the beauty of woodworking is that when armed with even a basic skill set, you can set out to build really usefull stuff that needn't look too shabby. As your skills improve, the range of projects available to you are limited only by your ability to imagineer solutions to the technical probs; there's always a range of ways to accomplish something...Mike Wallace
Stay safe....Have fun
mike where do you live? I go over sees every two three years to Ireland and or Scotland to play a little golf.
Kenney
I'm in Aberdeenshire.... tryin to avoid turning green with mould in this weather.....Mike Wallace
Stay safe....Have fun
Well said Wayne. Even I understood that 3 phase explanation.
;-)
Regards,
Ken
"Do as you would be done by." C.S. Lewis
Edited 3/16/2005 7:09 pm ET by kenshep
Wayne had a great explanation, I'll add that (from college radiology classes more years ago than I'll admit to) we were taught that 3-phase generators put our about 15% more effective power than single phase, which requires one to adjust techniques (exposure) depending on power supply.Regards,Leon Jester
Are you sure that the machine you purchased is 230 volt three phase and not just 230 volt. The reason I ask is that you say you are having a three phase plug installed. There is no way an average home has or can even get three phase power. I used to run a tool and Die shop and all our big machines were three phase, but for an average home shop it does not add up.
Keith
Keith what you wrote is correct. I just was not sure of it myself. We had a 220 outlet installed with the correct electrical outlet. I did not understand what 3 phase meant. I do now because of you and the others who responded. Also, the electrician I had install the outlet said that, homes do not recieve 3 phase power. So this all makes more sense now.
so in closing the 8' jointer came with a plug that looks like _ _
0
So i had my electrician install a 220 outlet with its own circuit breaker that would mate to that plug.
Thanks again for all your help
DJ-20's come with a 1.5 HP single-phase motor. The plug you show is a NEMA6-15P plug, 15 amp, 240V, 2 pole, 3 wire (i.e., 2 hots plus a ground). 'just what you'd find on a single-phase motor of this size.
Edited 4/19/2005 2:31 am ET by BarryO
just a note on three phase. Here in our rural area three phase is not available everywhere however some farmers have it to run their dryers on the grain bins. But where available our electric coop charges for power by using a surge meter. A person could run machinery one day of the month or all month long and pay the same bill depending on the load reached at any given time according to the surge meter. In other costly power bills!
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