Jointer 3 Phase Power Advantage

[Steve Mathews]

One of the advantages in 3 phase power for surface grinders is that it reduces ripples in the finish caused by pulses in the motor. Does that same advantage translate to jointers that use 3 phase power?

[Bill Dufour]

theoretically yes. In fact sanding afterwards makes it meaningless. With a surface grinder the finish is as ground and not touched again, ever.
Bil lD

[Jim Becker]

Any time there is a spinning knife, cutter head speed and feed rate are going to be the variables that will produce noticeable scalloping that has to be removed after milling by hand planing, scraping and/or sanding. The motor isn't going to contribute to that in a meaningful way, IMHO, and a jointer isn't a tool that's like a surfacing grinder used for precision metalwork. 3 phase does have the advantage of supporting more horsepower at a reasonable amperage and that can come into play if it's a "big tool".

[Darcy Warner]

An amp is an amp no matter what voltage or phase it is.

3 phase motors are simpler and way more durable than a single phase motor. I have numerous 3 phase motors well over 100 years old still running strong.

[Jim Becker]

That's true, Darcy, but the only practical way to get HP beyond about 5hp is by moving to 3 phase...hence, the larger machines tending to be so equipped.

[Dan Friedrichs]

I think the concept Jim is referring to is the fact that a 3 phase system can transmit more power per conductor area than a single phase system. So while "amps are amps" is true, you can power a larger machine than would be possible using the same total area of conductors than possible on single-phase: https://en.wikipedia.org/wiki/Three-phase_electric_power#Advantages

[Erik Loza]

One of the advantages in 3 phase power for surface grinders is that it reduces ripples in the finish caused by pulses in the motor. Does that same advantage translate to jointers that use 3 phase power?

Literally the first time I've ever heard this but curious. Gonna' try it out when I'm up in Dallas next. We have both in the shop. Would you only see it with a straight knife, though?

Erik

[George Makra]

Actually Jim that is incorrect you can get 7.5 HP all day long in single phase for about 350 and 10 HP is 1000 plus, for single phase an 15 HP is a couple grand.
As for pulses I call BS when you figure in inertia of the motor,drive train and moved object (cutter or what have you) it aint gonna decelerate and accelerate every 3300 or 5000 RPM or in the case of three phase times that by three.

[Bill Dufour]

An amp is an amp no matter what voltage or phase it is.

3 phase motors are simpler and way more durable than a single phase motor. I have numerous 3 phase motors well over 100 years old still running strong.


An amp is a amp but on three phase the amps are spread out between three conductors not two. So a three phase motor uses less amps. A single phase motor of equal horsepower will draw the three phase current times 1.732. I do not understand why it is not just 1/3 more amps.
1.732 is the square root of three.
Bill D

[David Kumm]

The balance of the head and pulleys, the belt quality and alignment, and even the bearing precision and clearance are bigger factors than three phase vs single. Enough other reasons to prefer three phase though. Dave

[Jim Becker]

Actually Jim that is incorrect you can get 7.5 HP all day long in single phase for about 350 and 10 HP is 1000 plus, for single phase an 15 HP is a couple grand..


I didn't say you couldn't get it...but I believe it's extremely uncommon in woodworking machinery to have uber-large single phase motors in the products you can commonly buy, at least with current machinery offerings. If you go shopping and want more than 5hp, the typical offering is more than likely going to be three phase...at least from what I've seen.

[Frank Pratt]

One of the advantages in 3 phase power for surface grinders is that it reduces ripples in the finish caused by pulses in the motor. Does that same advantage translate to jointers that use 3 phase power?

What is your source for this? I suspect that it is in theory only. I've never heard of that being an issue in real world applications.

[Bill Dufour]

Probably more significant results to balance the motor better then factory. Then balance each pulley with the set screws installed. Then it may be time to worry about three phase vs single phase.
Bill D

[Steve Mathews]

What is your source for this? I suspect that it is in theory only. I've never heard of that being an issue in real world applications.

No direct source that I can recall and I don't have much experience with surface grinders to back up my statement. I'm just a hobby machinist with a surface grinder. However I've been told and have read from experienced machinists that 3 phase motors are preferred on surface grinders because of their more consistent torque and stability. A search online will probably include some dissenting opinions but the overwhelming consensus makes sense to me based on what I understand of 3 phase motor construction.

[Dan Friedrichs]

Steve, I've heard that, too, and it has at least some theoretical basis. A 3-phase motor produces constant torque, while a single-phase motor produces pulsating torque. Whether or not that shows up in metalworking, I'm not sure.

[Erik Loza]

Literally the first time I've ever heard this but curious. Gonna' try it out when I'm up in Dallas next. We have both in the shop. Would you only see it with a straight knife, though?

Erik

Update: No apparent difference.

Erik

[Steve Mathews]

Update: No apparent difference.

Erik


Good to know. Sometimes actual experience is more practical than what one might expect from theory. Sounds like the theory only translates to metal grinding.