3HP 2 pole vs 2HP 4 pole

S

Sharpco

Joined
Mar 27, 2019
Messages
34
Hello.

Many guys said "4 pole is better than 2 pole for motor". I agree.

How about "3HP 2 pole vs 2HP 4 pole"?

I found this page.
http://dcknives.blogspot.com/p/grinder-motors.html
He said.........

--------------------------------------------------
Ideal Motors
We've looked at a lot of motor parameters so far and it's clear that some motors are better than others for a grinder build.

Ultimate
Three Phase
230 VAC
TEFC
1.5 to 3 Horsepower
2 Pole (3600 RPM)
4" Direct Drive Wheel
Variable Frequency Drive

Choice #2
TEFC
115/230 VAC
1 to 2 Horsepower
4 Pole (1800 RPM)
Counter-shaft with 4" Drive Wheel

Q: Is it true that running a motor slow can cause it to over heat?
A: Yes this is possible. However motor manufacturers often use the same fan for 2 pole (3600 RPM) and 4 pole (1800 RPM) in a given line of motors. Running a 2 pole slower less harmful than running a 4 pole slower. Running a 2 pole at 1/2 speed is the same as running a 4 pole at full speed.
--------------------------------------------------

How do you think about that?
 
There's a little more to it than just saying "slow motors can overheat", and it doesn't necessarily follow that a 2 pole (3600 RPM) motor has a lesser chance of overheating than a 4 pole (1800 RPM) motor. Yes, 2 pole motors spin faster, thereby drawing more air over the motor for the same given frequency, but what does that mean? Part of the equation is airflow, but you have to also factor in load on the motor.

Most makers (as far as I understand) are buying 4 pole motors because they have a little more torque at lower frequency (speed), but they will also "2x" their VFD to get 3600 RPM out of them. If you're doing a lot of slow grinding where you're really bearing down on your belt and loading down the grinder, then yes, you probably want to keep an eye on motor temps. For the average maker, however, it's likely going to be a non issue, as you're not typically grinding slow, long and hard enough to heat the motor past a critical temperature. I won't say it can't happen, or never happens, but it's probably not typical.

As far as the difference in lower end torque between 2 and 4 pole motors, this is another thing that the average maker is probably not going to notice very much if at all. The more noticeable difference will likely be the speeds.

As for 2hp vs 3hp... this again is going to be something that the average maker probably won't notice the difference in, unless you're really pushing into a larger platen or contact wheel and really hogging off a lot of metal.

TL;DR: You're probably not going to notice enough of a difference between the two options you listed to make it worth worrying about. Of course, that's just my opinion, YMMV.
 
Drew said it correctly - you'll never know the difference without looking at the name tag on a 2X72 grinder between a 1800 rpm motor setup to run at 3600 rpm or a 2 phole 3600 rpm motor. No difference what so ever in actual normal use.
 
Running a 4 pole motor at double speed to get 3600 RPM isn't harmful to the motor. It's the same bearings and shaft as the 2 pole that runs 3600.

Running a two pole motor at 5 hertz to achieve to the same speed as running a four pole motor at 10 hertz might not be good for it. It certainly will cog worse.

I like four pole motors for grinders on a VFD.
 
You must log in or register to reply here.
Back
Top