# Powering A Grinding Spindle With A DC Motor.



## Don B (May 30, 2014)

Is it practical to powering a Grinding Spindle with a DC motor, first off I know virtually nothing about electronics, this motor came from my CNC mill, it is a 92GN-BLM-300HA-300H-SMT DC motor, would this be possible/practical to make use of it to drive a grinding spindle.
I really have know Idea where to start or if this would cost more to make use of this motor than just buying a new motor..?:thinking:




Sorry I was unable to get a clear picture of the tag but I can write out the info if this is worth pursuing.


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## f350ca (May 30, 2014)

I used a DC treadmill motor on this tool grinder. A variable transformer controls the voltage, allowing me to set the spindle speed to 3600 for allumium oxide wheels or 5000 for diamond ones.




Sorry, no photos of tyne belt drive.
Greg


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## Don B (May 30, 2014)

f350ca said:


> I used a DC treadmill motor on this tool grinder. A variable transformer controls the voltage, allowing me to set the spindle speed to 3600 for allumium oxide wheels or 5000 for diamond ones.
> Greg



Ok thank you very much, it proves it's practical and that was one thing I was hoping for was the variable speed option, the problem I have now that I can see is this motor has 9 wires, I understand 2 wires and what happens when the polarity is switched... But..?
Could some one point to some reading material to figure out how to wire this, and does anyone maybe know how I can safely test this so me and the motor both live through it..?
As I said this came from my CNC and from what I could gleam it may have been the control board thingy that went, but I'm not sure.

Than you.
Don


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## JimDawson (May 30, 2014)

Don B said:


> Ok thank you very much, it proves it's practical and that was one thing I was hoping for was the variable speed option, the problem I have now that I can see is this motor has 9 wires, I understand 2 wires and what happens when the polarity is switched... But..?
> Could some one point to some reading material to figure out how to wire this, and does anyone maybe know how I can safely test this so me and the motor both live through it..?
> As I said this came from my CNC and from what I could gleam it may have been the control board thingy that went, but I'm not sure.
> 
> ...



Don the short answer is: yes it will work.  The problem is that it is a 3 phase motor.  BLDC = BrushLess Direct Current.  It needs to be powered by a BLDC controller.  This is actually a servo motor.  Once powered properly, you would have really precise speed control over your grinding wheel.

From the web site:  ''The whole system include brushless DC Motor (92BLM-GM-300HA,123BLM-IN-300HA) and brushless DC motor driver(BLMC-1100-300H, BLMC-2200-300HA), Function Board(SMT-1100), SMT-LCD''

http://www.everychina.com/products/...gn_blm_300ha_smt-29285921-zaf6667-detail.html


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## Don B (May 30, 2014)

JimDawson said:


> Don the short answer is: yes it will work.  The problem is that it is a 3 phase motor.  BLDC = BrushLess Direct Current.  It needs to be powered by a BLDC controller.  This is actually a servo motor.  Once powered properly, you would have really precise speed control over your grinding wheel.



Thank you Jim, so am I right in assuming there's now way for me to test this motor unless I purchase a "BLDC controller"
I'm probably really going to show my electronics ignorance with this question, but is there any type of re-wiring fix that could be done to the motor to make use of a simpler seed controller?


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## JimDawson (May 30, 2014)

Don B said:


> Thank you Jim, so am I right in assuming there's now way for me to test this motor unless I purchase a "BLDC controller"
> I'm probably really going to show my electronics ignorance with this question, but is there any type of re-wiring fix that could be done to the motor to make use of a simpler seed controller?



I'm pretty sure you could run that motor with a VFD.  I did a bit of research on the web sites and it looks like it is a 220V motor.  You should be able to confirm this from the data tag on the motor.  It should also have the power rating there.  I am a bit confused by the way the data is presented in the web site.  I can't tell what the power rating is from the part number, strange.

If you can get a picture of the data tag, or provide that information, I might be able to figure out what the proper VFD specs are.


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## Don B (May 30, 2014)

JimDawson said:


> I'm pretty sure you could run that motor with a VFD.  I did a bit of research on the web sites and it looks like it is a 220V motor.  You should be able to confirm this from the data tag on the motor.  It should also have the power rating there.  I am a bit confused by the way the data is presented in the web site.  I can't tell what the power rating is from the part number, strange.
> 
> If you can get a picture of the data tag, or provide that information, I might be able to figure out what the proper VFD specs are.



Jim, Thank you for taking the time to help, I'm not sure why I can't get a clear picture.

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

Line 1 --> Specifications -> DC300V - 1100W - 6000RPM - 4.5A - 1.8N.m

Line 2 --> Power Line -> Red (U) - Blue (V) - Black (W) - Yellow/green (GRD)

Line 3 --> Hall Line -> Red (+5V) - Black (GRD) - Yellow (SA) - Blue (SB) - Green (SC)

Line 4 --> Ip54 & Insulation Class F - Three Phase and 4 poles


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Is this OK, all Greek to me...?:thinking:


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## DMS (May 30, 2014)

I'm guessing you can't just pull the controller off of the mill the motor came off of? The easiest thing to do would be to find a replacement driver for that motor. I am guessing it would be cheaper than a VFD in any case.

LMS sells this, it may work. If you call or E-mail them they are very helpfull

http://littlemachineshop.com/products/product_view.php?ProductID=3995&category=-877015131


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## JimDawson (May 30, 2014)

Don B said:


> Jim, Thank you for taking the time to help, I'm not sure why I can't get a clear picture.
> 
> -----------------------------------------------------------------------------------------
> 
> ...




Line 1 is the most important for this discussion.

DC300V is the max operating Voltage

1100W is the power rating, approximately 1.5 HP

4.5A is the rated input current

1.8Nm is the rated torque, I think

So with this information the specifications for a VFD to run this motor:

Power rating  = 1.5HP or 1.1KW, probably 2HP rating is what you would want.

Assuming you only have single phase power available, you would want a VFD that will accept a single phase, 200V to 240V input.  this is pretty common.

There are a lot of VFDs available on ebay at reasonable prices.

I'm not going to provide free advertising, so I won't post the links.  If you decide to move ahead with this, I'll be happy to confirm the specifications.


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## frostheave (May 30, 2014)

Hi Don,

While I am not real "Hi-Speed" on motors, I don't think a VFD will work with your motor.  The "Hall" wires are for a sensor which is used by the controller to determine the motor speed.  They would not be used on a conventional VFD.

Many have had good luck replacing their stock DC controllers on their small mills with ones from KB Electronics.  They are reasonably priced and their website has some good info:

http://www.kbelectronics.com/Variable_Speed_DC_Drives.html

Bob


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## Don B (May 30, 2014)

DMS said:


> I'm guessing you can't just pull the controller off of the mill the motor came off of? The easiest thing to do would be to find a replacement driver for that motor. I am guessing it would be cheaper than a VFD in any case.



I do have the original Controller, but that's the thing I'm not sure what went wrong, Novakon wanted to charge me $100 plus the shipping to check it out, after the outstanding service I had received up until that point I past on the offer, died on the 4th piece, wonderful...!
Please excuse my terminology if it's off electronics just doesn't stick in my head, I looked around at what others had done and decided to invest the ($100 plus shipping) into a replacement motor, 3 phase and the board with a VFD.

Thank you for the advice, I'll check into this.

Don


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## JimDawson (May 30, 2014)

frostheave said:


> Hi Don,
> 
> While I am not real "Hi-Speed" on motors, I don't think a VFD will work with your motor.  The "Hall" wires are for a sensor which is used by the controller to determine the motor speed.  They would not be used on a conventional VFD.
> 
> ...




Bob, you are partly correct.  The Hall sensors are for very precise speed control on VFDs and servo drives that have the provision for that input.  They are also used for positioning in a closed loop servo system in CNC and other applications that require positioning accuracy.

In this application a variable output frequency from the VFD is all that is required to operate the motor as a standard 3 phase, the Hall wiring would not be used at all.  To the VFD, this motor would look like any standard 3 phase motor.

This motor is not a DC motor, so a DC speed controller would not work.

A BLDC motor is actually a 3 phase motor constructed with a permanent magnet armature so that they have the capability of producing near 100% torque at near 0 RPM and have a nearly flat torque curve over their speed range.


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## Don B (May 30, 2014)

frostheave said:


> Hi Don,
> 
> While I am not real "Hi-Speed" on motors, I don't think a VFD will work with your motor.  The "Hall" wires are for a sensor which is used by the controller to determine the motor speed.  They would not be used on a conventional VFD.
> 
> ...



Thank you Bob, I'll look into this, I guess I have some reading to do..!)

- - - Updated - - -



JimDawson said:


> A BLDC motor is actually a 3 phase motor constructed with a permanent magnet armature so that they have the capability of producing near 100% torque at near 0 RPM and have a nearly flat torque curve over their speed range.



Jim, thank you so much you have been so helpful.)


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## frostheave (May 30, 2014)

JimDawson said:


> Bob, you are partly correct.  The Hall sensors are for very precise speed control on VFDs and servo drives that have the provision for that input.  They are also used for positioning in a closed loop servo system in CNC and other applications that require positioning accuracy.
> 
> In this application a variable output frequency from the VFD is all that is required to operate the motor as a standard 3 phase, the Hall wiring would not be used at all.  To the VFD, this motor would look like any standard 3 phase motor.
> 
> ...



Hi Jim,

Thanks for the info, although now I am confused, which is not unusual!  I see that the link I posted does not apply to that specific motor as they are not BLDC drives, OOPS.  So here is my question.  After some reading, BLDC motors require some type of closed loop feedback, either hall effect sensors or back-emf.  How would a VFD drive a BLDC motor?  Does it sense the back-emf for proper commutation?

Thanks for your help,
Bob

- - - Updated - - -



Don B said:


> Thank you Bob, I'll look into this, I guess I have some reading to do..!)
> 
> - - - Updated - - -
> 
> ...



Don,

Jim was kind enough to straighten me out on the motor driver.  Please disregard the link I posted as those drives not apply to your motor.  Sorry about that.

Bob


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## JimDawson (May 30, 2014)

frostheave said:


> Hi Jim,
> 
> Thanks for the info, although now I am confused, which is not unusual!  I see that the link I posted does not apply to that specific motor as they are not BLDC drives, OOPS.  So here is my question.  After some reading, BLDC motors require some type of closed loop feedback, either hall effect sensors or back-emf.  How would a VFD drive a BLDC motor?  Does it sense the back-emf for proper commutation?
> 
> ...




Bob, again you are partly correct.  The feedback loop is required for speed control if the controller does not output a set frequency via a phase locked loop internal in the controller.  There are VFDs with what is called Sensorless Vector Control, those do sense the back EMF for commutation.

It really depends on the application that the motor will be used in.  Normally you would never use a BLDC motor in an application where a standard motor would do just because of the cost difference (like running a grinder), but if you have one laying around....  A BLDC motor would be happy running off of the 60Hz, 3 phase line without any control system ahead of the motor.  (assuming the voltage was correct).

We normally think of 3 phase motors as being something you would find in an industrial environment, running heavy machinery.  This is not so much the case today.  BLDC motors are everywhere, from model RC cars and aircraft and small battery power tools, to heavy industrial machinery.  Most of the new battery drills have BLDC motors in them and the feedback loop is via the trigger.

I hope this makes sense.


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## frostheave (May 30, 2014)

JimDawson said:


> Bob, again you are partly correct.  The feedback loop is required for speed control if the controller does not output a set frequency via a phase locked loop internal in the controller.  There are VFDs with what is called Sensorless Vector Control, those do sense the back EMF for commutation.
> 
> It really depends on the application that the motor will be used in.  Normally you would never use a BLDC motor in an application where a standard motor would do just because of the cost difference (like running a grinder), but if you have one laying around....  A BLDC motor would be happy running off of the 60Hz, 3 phase line without any control system ahead of the motor.  (assuming the voltage was correct).
> 
> ...



Thanks Jim.  It's starting to make more sense, but now I really have a lot of questions!  Maybe I'll start a new post.  At the risk of hijacking this thread, I would like to ask one more.

I have an Optimum BF30 mill and the motor has significant cogging.  The manufacturers tech has told me he believes their motor driver is sub par.  Do you think I could connect my 2HP Teco VFD to the mill motor and see if it runs better?  I would run the motor under no load as it is rated at 3HP, 2200W.  Below are the specs.





Thanks for your help.

Bob


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## JimDawson (May 30, 2014)

frostheave said:


> Thanks Jim.  It's starting to make more sense, but now I really have a lot of questions!  Maybe I'll start a new post.  At the risk of hijacking this thread, I would like to ask one more.
> 
> I have an Optimum BF30 mill and the motor has significant cogging.  The manufacturers tech has told me he believes their motor driver is sub par.  Do you think I could connect my 2HP Teco VFD to the mill motor and see if it runs better?  I would run the motor under no load as it is rated at 3HP, 2200W.  Below are the specs.
> 
> ...



It should work OK for testing.  I would start at maybe 15% speed and dial it up slowly while watching the amps on the display, don't let it go much over the max rated amps for the VFD.  VFDs will generally take about 115% of max amps without complaining too much.  I don't know how to display the amps on that unit, but normally you just push the up or down programming arrows to change what parameter is displayed while running.  Then turn the speed down again before hitting the stop button.

The VFD will limit the output current to keep it's self from self destructing.


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## frostheave (May 30, 2014)

JimDawson said:


> It should work OK for testing.  I would start at maybe 15% speed and dial it up slowly while watching the amps on the display, don't let it go much over the max rated amps for the VFD.  VFDs will generally take about 115% of max amps without complaining too much.  I don't know how to display the amps on that unit, but normally you just push the up or down programming arrows to change what parameter is displayed while running.  Then turn the speed down again before hitting the stop button.
> 
> The VFD will limit the output current to keep it's self from self destructing.



Excellent, thank-you Jim.  I'll give it a try.

Bob


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## JimDawson (May 30, 2014)

frostheave said:


> Excellent, thank-you Jim.  I'll give it a try.
> 
> Bob



Please let me know how that works out.  I expect that you may get some cogging at low RPM, but is should smooth out as the speed comes up a bit.


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## Don B (May 31, 2014)

frostheave said:


> Thanks Jim.  It's starting to make more sense, but now I really have a lot of questions!  Maybe I'll start a new post.  At the risk of hijacking this thread, I would like to ask one more.
> 
> I have an Optimum BF30 mill and the motor has significant cogging.  The manufacturers tech has told me he believes their motor driver is sub par.  Do you think I could connect my 2HP Teco VFD to the mill motor and see if it runs better?  I would run the motor under no load as it is rated at 3HP, 2200W.  Below are the specs.
> 
> Bob



Hi Bob, no worries about the thread the question suits the spirit of it, and it's interesting, could you please tell me what you mean by "cogging"
When I looked it up it said "_Cogging_ means that when you turn _the motor_ by hand it jumps from one magnet pole to the next and feels bumpy when you turn it" but I'm thinking you might mean something about how it running.


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## JimDawson (May 31, 2014)

Don B said:


> Hi Bob, no worries about the thread the question suits the spirit of it, and it's interesting, could you please tell me what you mean by "cogging"
> When I looked it up it said "_Cogging_ means that when you turn _the motor_ by hand it jumps from one magnet pole to the next and feels bumpy when you turn it" but I'm thinking you might mean something about how it running.



Pretty much the same thing applies when running at very low RPM,  This is where the commutation comes into play from the controller when connected to the Hall sensor.  This effect should go away as the speed comes up a bit.  The internals of a BLDC motor look somewhat like a stepper motor.


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## frostheave (May 31, 2014)

Don B said:


> Hi Bob, no worries about the thread the question suits the spirit of it, and it's interesting, could you please tell me what you mean by "cogging"
> When I looked it up it said "_Cogging_ means that when you turn _the motor_ by hand it jumps from one magnet pole to the next and feels bumpy when you turn it" but I'm thinking you might mean something about how it running.



Hi Don,
What I mean by cogging is, instead of the motor turning smoothly at a constant rpm, the speed varies, mostly at low rpm.  The thing is, it does not vary consistently, like once every second.  It happens at an inconsistent and seemingly random rate.  I know this is happening because of the sound the mill makes.  I can hear the speed changes as the pitch of the sound varies.  The problem is compounded because the quality of the gear meshing isn't great, i.e. the gearbox has a lot of slop.  This results in a VERY noisy mill that is no fun to use.

I talked to the Optimum tech and he said the problems I am experiencing are due to a poor motor driver design and the sloppy meshing of gears in the gearbox.  Short of a belt drive, I can't do much about the gearbox.  With the realization my BLDC motor can be run with a VFD, thanks to Jim Dawson, I want to see if the VFD makes a significant difference.  Maybe with a proper motor driver the mill will quiet down.  I will report back with my findings.

Bob


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## JimDawson (Jun 4, 2014)

I had a chance to play with a small (about 400 Watt) BLDC motor a couple of days ago.  This particular one is powering an electric bicycle, 36 volt power.

What I found was that it didn't seem to make any difference if the Hall sensor was connected to the controller or not.  It seem to run just the same, and was smooth running throughout its speed range.  In this case the operator is providing the feedback for speed control.  From this I think I can conclude that running a BLDC motor with a VFD should work well, but I still haven't had a chance to actually try it.


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