Variable Speed Motor Advice for KMG Grinder

C

CaptainFill

Joined
Mar 30, 2015
Messages
58
Hello,

I'm looking at purchasing a KMG grinder and am looking at what options I have for a variable speed motor. I see that the difference in price between just the grinder vs. grinder and variable speed is nearly a grand but I am convinced that I can do it for cheaper.

I am thinking that a variac speed controller might do the trick. I found a relatively inexpensive one with a 20 amp limit which would be plenty for a 1.5 hp motor. http://www.ebay.com/itm/NEW-Variac-...KM-/171850762306?_trksid=p2141725.m3641.l6368

The question is what type of motor would be capable of using something like this? Would I need a 3-phase?

Thank you much!
 
NO


If you use that you will smoke a motor

If you don't believe me, search for the other threads on this.




If you spend $100 on a variac, what are you saving ?



Buy the KBAC-27D from a local supplier if you can wire it up yourself =saved $

Buy an unsealed Nema 1 like a TECo50 wire it yourself, make your own enclosure, or take the chance metal sparks will smoke it
$200 ish
But they need 220v input


KBAC-27D
Will run 1.5hp and plug into any 110v 15 amp plug, in a sealed unit.
 
The KBAC is a very popular VFD on these forums. People love them, that says something. However if you are looking for something a little less spendy there are plenty of cheaper options on ebay. Something like this
http://www.ebay.com/sch/i.html?_sacat=0&_nkw=vfd 2hp&rt=nc&LH_PrefLoc=3&_trksid=p2045573.m1684

If you go that route though you will need to put some time into figuring out how to configure it. Also you will need to figure out an enclosure for it though because the steel dust will kill it. Lots of good info on on how to do this on this and other forums.

And yes you will require a 3 phase motor.





*Edited link
 
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Teco FM50 works for me. I put it in a sealed toolbox, and I haven't looked back. I run 2, 2hp motors and 3/4hp motor off this drive using a switch routing box to send the output where it needs to go. A VFD is needed to be able to keep torque up at lower speeds. A variable AC setup will cut speed, but it will also eliminate the torque needed to keep grinding when pressing firmly into a grinding belt. It will also, as the count suggested, smoke your motor eventually.

The filters were are there so I could pull filtered air through if necessary, but I haven't found the need.


--nathan
 
silver_pilate said:
Teco FM50 works for me. I put it in a sealed toolbox, and I haven't looked back. I run 2, 2hp motors and 3/4hp motor off this drive using a switch routing box to send the output where it needs to go. A VFD is needed to be able to keep torque up at lower speeds. A variable AC setup will cut speed, but it will also eliminate the torque needed to keep grinding when pressing firmly into a grinding belt. It will also, as the count suggested, smoke your motor eventually.

The filters were are there so I could pull filtered air through if necessary, but I haven't found the need.
--nathan
Click to expand...

Careful for others reading this -- one is never supposed to have any switch/disconnect between the VFD's output and the motor that can be switched off while the VFD is running.

The metal box is a good idea on a non-NEMA 4x VFD, though. Make sure the back/heatsink portion of the VFD is directly against the metal box for cooling purposes.
 
Yes, always wait until the motor is stopped prior to switching output locations. That and make sure you have appropriately rated switches and you'll be ok.
 
Thank you all for the input! Especially the not to use a variac one ;)

I like the FM50 option and feel that I would be capable of making something like this work with a proper enclosure. A problem that I do forsee however is that the only available 115v model (which is the only power supply in my workshop) supports up to 1 hp motor while the 230v supports up to 3 hp. I'd like to use a 1.5 hp motor so the 115v version might be underpowered for my application?

Thank you all again!
 
12345678910 said:
NO


If you use that you will smoke a motor

If you don't believe me, search for the other threads on this.


If you spend $100 on a variac, what are you saving ?

Buy the KBAC-27D from a local supplier if you can wire it up yourself =saved $

Buy an unsealed Nema 1 like a TECo50 wire it yourself, make your own enclosure, or take the chance metal sparks will smoke it
$200 ish
But they need 220v input


KBAC-27D
Will run 1.5hp and plug into any 110v 15 amp plug, in a sealed unit.
Click to expand...

Plus one the TECO unit very easy to wire and the unit can do just about everything, I built the LB Wilmont Grinder with a 3Ph 1.5 HP motor and used the TECO EV/JNEV Series from Wolf automation. Works like a champ
 
CaptainFill said:
Thank you all for the input! Especially the not to use a variac one ;)

I like the FM50 option and feel that I would be capable of making something like this work with a proper enclosure. A problem that I do forsee however is that the only available 115v model (which is the only power supply in my workshop) supports up to 1 hp motor while the 230v supports up to 3 hp. I'd like to use a 1.5 hp motor so the 115v version might be underpowered for my application?

Thank you all again!
Click to expand...

How hard would it be to run a 220 line into your shop? I'm sure its something you've already considered, I just bring it up because I think you would be happy you did. If you are just starting to purchase tools/machines for your shop having the 220 is a big plus, opens the door to better options sometimes. If your current circuit is only 15 amp you will likely need to run a 20+ amp circuit anyway. Wouldn't cost much more to run a 220 line.
 
The most intuitive VFD IMO is the KBAC hybrid series, analog dial control, settable ramp up, ramp down, minimum speed, and maximum speed, reversable, etc. I've had to deal with their CS department as well when one of my VFDs started to act up 9 months after I bought it, and they were fantastic, having an actual engineer call me on the phone to step through diagnosis problems before sending it back to them and having the main board replaced at no cost to myself.

They're a bit more expensive than the equivalent from other manufacturers but they're bulletproof, (ok that's just figurative, but they are dust proof!)

For an example of how much I like them... Most of my equipment runs off of them.

rivettVFD.jpg


dupontVFD.jpg


kmg1.jpg
 
I would NOT plan on running a 1.5hp motor+VFD combo on 110v. The KBAC series VFD's are capable of doing this, but they will draw a lot of amps (something like 22+, which means you really need a 30amp circuit and might possibly, though not necessarily, squeeze by with a 25amp circuit). I would be surprised if you have a circuit that can reliably manage this. Therefore, plan to run your motor+VFD on a 220v single phase circuit. If this is a home-shop, then you'll probably find one of those for your washer/dryer, and maybe separate ones for garbage disposal and central A/C. By the way, you can probably run 2hp on the VFD on a 220v circuit.

Note that this is different than running a single phase 1.5hp motor. Most single phase 1.5hp motors draw 13.5-16 amps @115v, so you can run them on a 20amp 115v circuit (remember the circuit should be 25% greater amperage than your motor's nameplate amp draw).
 
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I think that my only bet will be to wire for 220, there are two circuits running into the workshop so it won't be too difficult but still a bit of a challenge. The reason why I am trying to find a way to make 110 work is because it opens my options for relocation where 110 might be the only option in something like a rental unit w/ garage. Ultimately 220 will be my best bet and will need to make proper arrangements to accommodate those requirements.

Does anybody know of a good yet budget friendly 1.5-2hp 3ph motor? I'd like <$300.

Thanks all again!
 
Those are both excellent motors! Do you think that the RPM will be sufficient with a direct drive? I feel like I would want to shoot for around 3500 rpm in that case.

Either way, excellent resources for finding one!
 
Personally I like the 1725 rpm and use the pulleys to set my speeds. I have a 1725 with a 5" motor pulley and 2" shaft pulley turning the drive wheel and it will hit that 4000 SFPM on the top end but I don't spend much time in that speed range. Here is a chart showing motor speeds and pulley combos and what the expected SFPM could reach.

http://www.engineeringtoolbox.com/pulley-motor-speed-d_1475.html
 
CaptainFill said:
Those are both excellent motors! Do you think that the RPM will be sufficient with a direct drive? I feel like I would want to shoot for around 3500 rpm in that case.

Either way, excellent resources for finding one!
Click to expand...

Not sure you would want to go more than 1750 RPM with a VFD. Most VFD's you can adjust over 60 Hz, some you can even run up to 200 Hz for sure you will shorten the motors life but you have that extra power when you need it. This one listed below is great unit and their tech support is awesome.

TECO
 
I just realized you said direct drive in which case you would need to calculate your drive wheel diameter. You will still have a really fast running machine with 3600 rpm.
 
Busto said:
I just realized you said direct drive in which case you would need to calculate your drive wheel diameter. You will still have a really fast running machine with 3600 rpm.
Click to expand...

That's what I was thinking with a 3600 RPM motor, I have a five" wheel on mine with a 1750 RPM motor and at 60 Hz I have plenty of speed and rarely do I go above that.
 
There has been a lot of debate on what the best RPM is for a grinder. I use a 1750RPM as I can set the KBAC-27 to 2x speed. This gives me plenty of torque at lower speed and with a 5" drive wheel top end is around 4,600 FPM. This works good for me.
 
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