Induction motor? 1

[bevins]

Hi all,

I need a motor and vfd while I am building a machine. Peoblem is I do not know much about motors. I have an older Dayton 1.5hp and a 5 hp dayton. models 3n222 and 2N998D respectively.

230 AC 3phase. Do you have to connect an induction motor to a vfd or any AC motor will do. How do I know if these motors are induction motors.

I cannoit find any info on these motors at all.

Any help would be appreciate4d.

Thanks in advance,

Bob

 

[waross]

Above 1 HP 99% of three phase motors are induction motors.
When you get above hundreds of HP synchronous motors start showing up.
If the nameplate doesn't identify the motor as a stepper, a servo, or a special purpose motor it is likely an induction motor.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[bevins]

Thanks for the reply.

I have another question. When I put the 1160RPM 230vac 3phase motor on a vfd, and use a 9" pully on the motor and a 3" pully on the shaft (lathe) I am turning, can I expect enough torque to at 3100 RPM?

Thanks,

Bob

 

[jraef]

Define "enough"...

Motor torque:
Tq (ft. lbs.) = 5252 x HP
_________
rpm

Then you have a speed increase ratio of 3:1 so you have torque REDUCTION of 1:3 at the final work shaft (less a small amount of mechanical transmission losses).

If your final work speed is 3100RPM, I would get a 2 pole (3600RPM) motor and use the VFD to lower the speed to other levels when necessary. No loss of torque in that process.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[ScottyUK]

Torque available at the high speed pulley will reduce by the same ratio that the speed increases, i.e. there is an inverse proportional relationship.

Whether there is 'enough' torque really depends on your load, and we don't know anything about your load.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[bevins]

Sorry,

It is going on a lathe for turning wood.

 

[jraef]

That doesn't do much for me and I am (was*) a hobby turner. Generally you want higher speeds for lighter / finer cuts and maybe polishing, so a decrease in torque with increased speed is usually not a big deal. But for all I know, you are planning on turning 6 foot diameter bowls made of green oak at 3100RPM... (if you are, let me know where you are so I can stay clear!).

Generally, and especially on wood lathes, I recommend that you start with a motor close to the highest speed you want to work at and use a VFD to turn it down, unless you have a stepped pulley. In that case, strive to attain the best torque at lower speed ratios, that's where you need it, and use the pulleys to speed up for the finish work.

* Wifey made me give up the space for my hobbies when the kids were born. 26 years later they're still here...


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[bevins]

I see. Thanks, Not going to be turning a big tree. If that were the case I think I would rather turn around the tree instead of the tree turning.

We are doing small pens and maybe some table legs.

This is the motor I have. I do have a 5hp motor that I may use instead then. It is 3500 RPM. Problem is the vfd is much more expensive for a 5hp motor.

Thanks,

 

[jraef]

5HP is serious serious overkill for turning pens and table legs. Even 1-1/5HP is overkill for that matter, 3/4HP is considered pretty decent power for a small wood lathe for things like that. I wouldn't worry at all about torque, use the 1-1/2HP and your step-up pulleys.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[bevins]

Thanks, you guys are great!

can I reserve one more question for connections? I know how it should be done but, just want to make sure before I do the actual connection.

Thanks again,

Bob

 

[jraef]

http://www.patchn.com/index.php?option=com_content&task=view&id=45&Itemid=34

"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[accordlx]

Keep in mind that induction motors made to run on VFD's are wound with inverter duty magnet wire. Some of the older motors cannot withstand the phase to phase voltage stresses when run off a vfd. Also cooling is an issue that needs to be considered as well. If the motor is going to be run at a reduced rpm, external cooling may be required.