Setting up disk sander- DC motors?

E

elementfe

Joined
May 3, 2008
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I'm setting up a disk grinder using the very cool Nielson quick change system, and wondering why more folks don't just use a rectifier and DC motor.
Not knowledgeable about electronics at all and hoping someone who is can enlighten me. Aren't DC motors much more friendly about speed control and reversing than AC?
Most of the shops I've been in use VFD on 3 phase AC, it seems like the long way around but there must be a reason that it's the most popular system.
Thanks for any ideas!
Andy G.
 
It cheaper to use 3ph motors and VFD unless you use recycled motors,power supply's and variable speed controls from treadmills like I do.
 
DC motors are a popular choice for speed control, but they require a controller that is more efficient than a Variac and a rectifier bridge. That will work for low horse power and low torque motors, but ones running sanders and grinders need a controller similar to the VFDs used for 3 Phase. KB-C makes them and they are pretty much identical to the VFD controls, just with DC output and field/armature voltages. For a VS disc sander, a 1HP 180VDC motor is a good choice. The KB-PC 240D is a good choice for a controller.
 
bladsmth said:
DC motors are a popular choice for speed control, but they require a controller that is more efficient than a Variac and a rectifier bridge. That will work for low horse power and low torque motors, but ones running sanders and grinders need a controller similar to the VFDs used for 3 Phase. KB-C makes them and they are pretty much identical to the VFD controls, just with DC output and field/armature voltages. For a VS disc sander, a 1HP 180VDC motor is a good choice. The KB-PC 240D is a good choice for a controller.
Click to expand...

elementfe said:
I'm setting up a disk grinder using the very cool Nielson quick change system, and wondering why more folks don't just use a rectifier and DC motor.
Not knowledgeable about electronics at all and hoping someone who is can enlighten me. Aren't DC motors much more friendly about speed control and reversing than AC?
Most of the shops I've been in use VFD on 3 phase AC, it seems like the long way around but there must be a reason that it's the most popular system.
Thanks for any ideas!
Andy G.
Click to expand...

The DC controllers are about 1/3 the price of the AC VFD controllers

The trouble is that the DC motors are much more rare and expensive.
 
Thanks for the input, everyone! I may see about a treadmill motor, if that seems like a good way to go.
 
elementfe said:
Thanks for the input, everyone! I may see about a treadmill motor, if that seems like a good way to go.
Click to expand...

Are you buying a premade disc?

treadmill motors may not fit the shaft size and mounting

Also, they are likely to be open unsealed motors subject to steel dust intrusion.
 
Thanks, Count- ripping old stuff apart and making new stuff out of it carries a lot of issues, doesn't it.

Thanks, Scott, for the link- that got me to: http://dealerselectric.com/item.asp?cID=0&PID=6899
which is a 3/4 hp with vfd. and the 5/8 shaft I need.
Can anyone more knowledgeable than me tell how close that would get me to a reversible variable setup? None of these VFDs mention reverse...
I can certainly do brackets and so forth.
 
elementfe said:
Thanks, Count- ripping old stuff apart and making new stuff out of it carries a lot of issues, doesn't it.

Thanks, Scott, for the link- that got me to: http://dealerselectric.com/item.asp?cID=0&PID=6899
which is a 3/4 hp with vfd. and the 5/8 shaft I need.
Can anyone more knowledgeable than me tell how close that would get me to a reversible variable setup? None of these VFDs mention reverse...
I can certainly do brackets and so forth.
Click to expand...

I did a diagram with a tweco showing how to reverse.
download the manual

It's one switch and three wires.


FM50page17wiringdiagram-EDITING.gif


This came from an origional manual and was edited

Skip the footswitch if you want

read the actual manual for you unit and verify
 
Ah, very cool, Count!
I wired my house and shop no problem, but when you get into circuit boards and resistors and all that it looks like voodoo.
Thanks for all the help, people.
 
Mooseyard said:
I don't think that motor will work for a disc grinder because of the shaft size. Also, you will need to make a dust tight enclosure to prevent the VFD from getting metal dust in it.
Click to expand...

This variable frequency drive & three phase motor package consists of the following: VFD: is a 1 HP, 115V Single Phase Input-230V Three Phase Output, Teco Westinghouse, Model #: JNEV-101-H1, constant torque sensorless vector drive, HEIGHT = 5.20, WIDTH = 3.03, DEPTH = 5.13, 3 LBS., IP 20 Enclosure. Motor: is a Brook Crompton, Model #: FA4N.75-2, aluminum construction TEFC, NEMA 56 Frame motor. Shaft Dimensions: .625" Diameter, 1.88" Length. - See more at: http://dealerselectric.com/item.asp?cID=0&PID=6899#sthash.0ps8O1rJ.dpuf


I agree on a dust proof controller box.


What's the problem with the shaft size?

The Neilson disc is 5/8" and so is the motor


http://www.nielsendesigndiscgrinder.com/About_the_Disc_Grinder.html
 
On my disc grinder I have a similar set up I bought from them only difference was a reliant motor. I have been using the variable speed by Teco I have it in a box to protect it somewhat and I just blow all my equipment out once a week with compressed air. So you will get at least a year out of it marginally protected. The buttons to control it are all cracked from constant use. Just for reference I used it 7 days a week for a year on my old grinder before it went to its new life of a disc grinder . so not to bad for the money spent.

Count ! Thanks for the wiring diagram I lost my manual and I was thinking about reverse. For what I use it for probably doesn't really mater either way. But nice to know.

I have the KB on my KMG I got from Rob. I like that drive much better because of just having the knob. Plus its just a well built unit.
 
Marko3 said:
On my disc grinder I have a similar set up I bought from them only difference was a reliant motor. I have been using the variable speed by Teco I have it in a box to protect it somewhat and I just blow all my equipment out once a week with compressed air. So you will get at least a year out of it marginally protected. The buttons to control it are all cracked from constant use. Just for reference I used it 7 days a week for a year on my old grinder before it went to its new life of a disc grinder . so not to bad for the money spent.

Count ! Thanks for the wiring diagram I lost my manual and I was thinking about reverse. For what I use it for probably doesn't really mater either way. But nice to know.

I have the KB on my KMG I got from Rob. I like that drive much better because of just having the knob. Plus its just a well built unit.
Click to expand...

I you look in the digram above, Pins 8, 9, 10 is for an external potentiometer knob

Maye a 10K Ohm linear potentiometer would do it.
Read the manual to get it right and - maybe some other settings to change.
 
12345678910 said:
I you look in the digram above, Pins 8, 9, 10 is for an external potentiometer knob

Maye a 10K Ohm linear potentiometer would do it.
Read the manual to get it right and - maybe some other settings to change.
Click to expand...

I have seen some great setups with this type of vfd with a remote on off button an dial pot all mounted in the same nema4 box. Those boxes are pricy.
 
12345678910 said:
This variable frequency drive & three phase motor package consists of the following: VFD: is a 1 HP, 115V Single Phase Input-230V Three Phase Output, Teco Westinghouse, Model #: JNEV-101-H1, constant torque sensorless vector drive, HEIGHT = 5.20, WIDTH = 3.03, DEPTH = 5.13, 3 LBS., IP 20 Enclosure. Motor: is a Brook Crompton, Model #: FA4N.75-2, aluminum construction TEFC, NEMA 56 Frame motor. Shaft Dimensions: .625" Diameter, 1.88" Length. - See more at: http://dealerselectric.com/item.asp?cID=0&PID=6899#sthash.0ps8O1rJ.dpuf


I agree on a dust proof controller box.


What's the problem with the shaft size?

The Neilson disc is 5/8" and so is the motor


http://www.nielsendesigndiscgrinder.com/About_the_Disc_Grinder.html
Click to expand...
The link I followed was a 1 hp with a .875 shaft that Scott posted. The link you have is the 3/4 hp which will work fine.
 
Just a quick followup- I ordered the motor and controller from the Dealers Electric, it shipped right away, arrived in exactly the week estimated.
Though the package was tossed around a bit in transit, all was expertly packed, and arrived in perfect condition.
Quality appears to be very good, and a preliminary hookup and test shows all working well.
Thanks for all the input!
Andy
 
I have one of the earlier KMG grinders with the VFD/AC motor setup. I asked them why the switched from DC motors and they told me that the VFD/AC setup was a lot more reliable. Take that for what it is worth.
 
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