# Variable or constant torque VFD for a 3 p Baldor grinder?



## Glenn Brooks (Oct 19, 2017)

Hi all,   

Here's yet another very basic  VFD question -  would  a 3 phase Baldor commercial grade grinder need a constant torque or variable torque VFD?  

I assume it would be a constant torque application - but really, know almost nothing about VFD's.  All my few 3 p machines run directly off an RPC.  

Background:  I am  trying to sort out buying a VFD to power a Baldor 220v 3P grinder I recently bought.  Don't really want to run a new 3P circuit and conduit across the shop for this one piece of equipment.  So am thinking about adding a cheap VFD to convert 1P to 3P at the work station.


Also, any recommendations on good versus not so good brands of VFD's and vendors these days??

Thanks 

Glenn


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## mksj (Oct 20, 2017)

Usually you want constant torque in this application, a common VFD used in this application (grinders and belt sanders) is the KB Electronics KBAC or  KBDA, these are sealed VFDs so NEMA 4x. These would not require a separate enclosure, so that needs to be factored into the total cost. They do not have the flexibility (inputs and programming) of most VFDs, but they work very well in this application. There are other NEMA 4x VFDs, but they are more expensive. Teco E510 is an alternative with more features, but I would stay with the KBAC.
http://www.kbelectronics.com/Variable_Speed_AC_Drives_Inverters/AC_Drives_NEMA_4X.html


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## Karl_T (Oct 20, 2017)

I'd just shop for value, not a critical application here.

My 2 cents, automation direct has great VFDs for a fair price. i'd go GS2 series for this:
https://www.automationdirect.com/ad...Drive_Units_(115_-z-_230_-z-_460_-z-_575_VAC)


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## Glenn Brooks (Oct 20, 2017)

Thanks guys, 

One other question I forgot to ask.  When selecting VFD HP, Do you directly match the HP rating  of the motor, or double it, to handle start up power surge requirements and overloads?

Thanks again,
Glenn


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## JimDawson (Oct 20, 2017)

If the grinder is 3 HP or under, then Automation Direct (and many other vendors) have single phase input VFDs that will run it without oversizing.  Most will handle a 150% overload for some short period of time.  All of them will handle the starting load.  Setting the acceleration parameter to > 10 seconds will minimize the starting load.  I agree with @Karl_T that a GS2 would work for a bench grinder type application.  I would assume that for a grinder you would just set the VFD at 60Hz and leave it there.


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## woodchucker (Oct 20, 2017)

Glenn Brooks said:


> Hi all,
> 
> Here's yet another very basic  VFD question -  would  a 3 phase Baldor commercial grade grinder need a constant torque or variable torque VFD?
> 
> ...


Why not just get a small static converter for the one machine. It's not a machine that you would run a different speeds or reverse.


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## Karl_T (Oct 20, 2017)

woodchucker said:


> Why not just get a small static converter for the one machine. It's not a machine that you would run a different speeds or reverse.



Yep, if you want to be REAL CHEAP, just hold in about 250 MFD start caps per hp between one of the single phase legs and your wild leg for about two seconds. the grinder should start right up.


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## woodchucker (Oct 20, 2017)

Karl_T said:


> Yep, if you want to be REAL CHEAP, just hold in about 250 MFD start caps per hp between one of the single phase legs and your wild leg for about two seconds. the grinder should start right up.



A static converter is a VFD that is not variable right?  So why put the REAL CHEAP comment,, it's a real alternative for about $150-220.
Are you making it like a low quality solution. 
And are you saying that it won't start w/o a set of CAPS in line.  While I have a rotary I have watched a guy light up some very big equipment on a static. Only 1 machine runs on it at a time. But it seems to carry the load pretty well.


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## Glenn Brooks (Oct 20, 2017)

So what's the advantage of a static converter over a  VFD, or vice versa?  They both can be had in the $150 price range.

Obviously I don't know much about either.

Glenn


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## woodchucker (Oct 20, 2017)

Simplicity. Are you planning on using the Grinder at different speeds? If not, then the static converter supplies simple 3 phase power. The VFD , more complex power, as it is VARIABLE.  If you need Variable, then VFD, if you need power, the Static is all you'll need. It's just like a Rotary but doesn't handle the load that a Rotary will. A rotary will handle multiple machines, while Static only handles one at a time well. Much the same as a VFD. You can set the Static up with plug to single phase and a plug for the 3Ph if you wanted to, so you can use more than one machine, just unplug and plug in the other machine. Generally with the VFD you will hardwire. With the Static it's not unusual to use a twist lock.


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## Karl_T (Oct 20, 2017)

woodchucker said:


> A static converter is a VFD that is not variable right?  So why put the REAL CHEAP comment,, it's a real alternative for about $150-220.
> Are you making it like a low quality solution.
> And are you saying that it won't start w/o a set of CAPS in line.  While I have a rotary I have watched a guy light up some very big equipment on a static. Only 1 machine runs on it at a time. But it seems to carry the load pretty well.


This would be over most folks head, but you can make a three phase motor start on single phase with just a few start caps held in for a couple seconds. for those interested, this can be done for less than $50. Info on how to this is readily availble on the web.

Myself, i suggest the 110 volt VFD so the grinder can be plugged into any wall outlet.


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## Glenn Brooks (Oct 20, 2017)

Actually I have a 220 single phase circuit right where I want the grinder to sit. So will go with a simple VFD 220 to 220 3 phase unit.  TECo and Hitachi have them in constant speed configuration for around $150-$170, depending on vendor. 

Probably could have saved myself from installing even tthe 220v but last time I looked at VFD's - a year ago or more - 110v to 220 3 phase VFD's werent really ready for prime time.  Didn't do much aka any due diligence when thinking about power supplies, when acquiring this grinder. Traded it for an old Delta drill press.  

The other time I ve been reading is that static converters only use about 60% of horse power, so you need to buy a bigger unit to compensate, then pay the extra utility bill.  whereas VFD's are up around high 90's to 100% of rated HP.   So more efficient.  Probably doesn't make a big difference in my shop as the grinder will be occasional use.  But, it will be a good citizen when it cranks up. 

Glenn


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## Ulma Doctor (Oct 21, 2017)

the biggest hurdle in using a static converter is starting the intended motor quickly.
once the grinder motor is running, it will generate the third leg through induction.
it is not as efficient as 3 phase supply or a VFD, but you could build a motor starting system for less than $50
with parts from ebay
here is a set up i did for giggles, i had a spare contactor
this is a simple model, overload protection was omitted for simplicity





if you need help in making a starter, i'm more than happy to help- or make one for you


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## Glenn Brooks (Oct 21, 2017)

Hi Mike,

Hey, great video.  This is very cool!  I might be interested in making this up from scratch.  I think It would be a very interesting learning project, particularily if you can stand some possible rudimentary questions from an inept, electrically challenged old guy.

Couple of questions about your video:

What is the best way to secure all the components in a case?  For example, I didn't notice any mounting brackets on the capacitor.

Also Is each component tied into ground? If not, what parts should be grounded?

What size wiring did you use for the connections?

What would be a proper mounting board/frame?

What about overload protection and a circuit breaker? 

I need to confirm motor size - I think it is either 3/4 hp or 1 hp.  Same size components for this size motor, as themparts you used ?

Iam thinking this assembly would ideally be mounted in the U shaped column that the grinder is bolted to.  Off/on buttons around front somehow.   Mine is a floor mounted column with grinder motor at about waist height - 8" X1" grinding wheels.

We have a local old school electrical supply shop near by that likely has all the parts in your video in stock.

Thanks
Glenn


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## CluelessNewB (Oct 21, 2017)

woodchucker said:


> A static converter is a VFD that is not variable right?



No a static converter is NOT a VFD that is not variable.  A static converter will only allow the motor to deliver about 2/3 it's rated power.  A VFD will allow the motor to delver it's full rated power.   The only advantage of a static converter is the low cost.


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## Ulma Doctor (Oct 21, 2017)

Glenn Brooks said:


> Hi Mike,
> 
> Hey, great video.  This is very cool!  I might be interested in making this up from scratch.  I think It would be a very interesting learning project, particularily if you can stand some possible rudimentary questions from an inept, electrically challenged old guy.
> 
> ...



Hi Glenn,
thank you for your kind words.
as far as securing components in an enclosure, you can use DIN rails for attachment or you can use bolts, aircraft nuts, and washers.
for attachment of the capacitor, zip ties work wonders. ( commercial cap brackets are available if you want them)

for this operation, you'll ground the motor to the input ground- no other component grounding is necessary

for the control wiring for the switches and capacitor, i used 18 gauge stranded wire
you could use heavier wire if you choose.

For the motor wiring, you may wish to use 14 gauge  or  12 gauge if you are going to pull more than 20 amps

you can get enclosures from the big box stores for less than $20, that will suffice

overload protection can be accomplished by 4 fuses and 4 fusseholders (2- 1a control fuses and 2- 10 amp system input fuses)
or
you can use a 10-12 amp overload relay and 2 control fuses of 1a capacity

you can get away with a smaller contactor, because the load is small.

we can even add a balancing capacitor to gain back some lost HP 

if you have other questions, i'm happy to assist in any way i can


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## mksj (Oct 21, 2017)

If your grinder is 1 Hp, and then you consider you will loose maybe 30% of the power with a static converter, you are left with a pretty whimpy grinder. You can pick up a 1 Hp Teco L510 for $125, a 2Hp for $175, and it will have overload and short circuit protection. They can also provide up to 150% overload for up to 1 minute, so the grinder will not bog down. Going up a size (2 Hp), would allow you to use the VFD on other machinery, or should you decide to get a larger grinder/machine at a later point.  Metal dust can be an issue, but you could mount the VFD a few feet away on a wall and just add a socket plug to the input and it can easily be moved.  I often will put the VFD in an open faced (no cover plate) inexpensive electrical box or put a flat shelf 6-8" above the VFD so nothing falls into it. Fine to make your own static converter, but the parts/enclosure will probably cost you more than one that you can buy wired and ready to go for about $45 including shipping.
http://dealerselectric.com/L510-201-H1-N.asp
http://dealerselectric.com/L510-202-H1-N.asp
https://www.ebay.com/itm/HD-1-3-Hp-...athe-Saw-USA-single-three-SCM03-/281623703425


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## Glenn Brooks (Oct 23, 2017)

Thanks everyone.  Finally decided to buy a TECO VFD on sale from Dealers electric - actually went with a 110v input -3 phase output unit.  Mostly to expedite resale down the road.

Also the HP rating on the motor in 3/4 HP.  And I didn't want to loose 1/3rd of that with a static converter set up.

Now hopefully I can figure out to install and set up parameters when the box arrives.  On to the next project in my shop upgrade!

Glenn


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## Bob Korves (Oct 23, 2017)

Glenn Brooks said:


> Now hopefully I can figure out to install and set up parameters when the box arrives.


There is plenty of help for you here on H-M, Glenn, and that Teco should be pretty straightforward to set up.


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## Glenn Brooks (Oct 27, 2017)

Well, I hooked up the teco VFD and the unit only runs the grinder at slow idle.  

So  I learned on line that I need to program the unit, as apparently none of the parameters are preset.

any advice would be appreciated.

Thanks
Glenn


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## mksj (Oct 27, 2017)

Power up the VFD, it should initially show the output voltage which is 220V, then after 2 seconds display the frequency set point. So you are seeing the frequency set point, assume it shows 5.00. You press the MODE button to cycle through the different display modes, see P4-5. At the frequency display screen it will show up as 5.00 at 5Hz, 60.00 at 60Hz. If you want to change it using the default setting which is from the keypad, do a short press on the ENT key to access each digit, use the UP and DOWN key to change that digit, then press do a short press of the ENT key to confirm the entry and move (shift) to the next digit. This sets each digit of the parameter.  If you want 60.00 Hz, press four short ENT key pushes until you are at the tens digits, then press the up key till you reach 6, so the display reads 60.00. Press and HOLD the ENT hey to confirm any changes. To exist the program and confirm that entry, usually just press and hold the ENT key for a few seconds. Pressing the ENT key for more than a few seconds brings you back to the previous menu level and confims the change. If this is not done the change will not be entered into memory, sand will not stick.  This is outlined on Page 4-7.


You will also need to program the parameters below as a starting point, PRESS the Mode Key until you see the 00-01 programming display, and press the ENT key. Use the UP DOWN key to select the number for each digit of the programming parameter you want to change, then press ENT to move to the next digit.  When the you have reached the parameter to modify, hold the ENT key for more than 2 seconds and then modify the parameter value, when done entering each digit press and hold the ENT key to bring you back out to the next menu up. You must press and HOLD the ENT key for a setting to be entered once you have changed the digit(s) for that parameter. A short press of the ENT  is to shift to the next digit to change.

*Group 00- The basic parameters group*
*Setting*
*00-05 *Main Frequency Source Selection CHANGE THIS PARAMETER TO "1" : Potentiometer on Keypad
*00-14 *Acceleration Time I WOULD RECOMMEND SETTING THIS TO 5.0 seconds
*00-15 *Deceleration Time I WOULD RECOMMEND SETTING THIS TO 5.0 seconds

*Group 02- Motor parameters*
*Setting*
*02-00 *Motor No Load Current - factory default
*02-01 *Motor Rated Current SET TO YOU MOTOR CURRENT _ _ . _ A
*02-02 *Motor rated Slip- factory default
*02-03 *Motor Rated Speed SET TO YOUR MOTOR RATED RPM _ _ _ _ 
*02-04 *Motor Rated Voltage SET TO YOUR MOTOR RATED VOLTAGE _ _ _ . _ V

*Group 11: Auxiliary Parameters*
*11-01 *Carrier Frequency (kHz), I would set to 8 Khz, default is 5.

If you are unclear on any of the parameters, let me know or PM me and I can give you some recommendations.
Mark


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## Glenn Brooks (Oct 27, 2017)

Thanks Mark,

One immediate question.  If I set the frequency to 60hz, does that mean when I turn on the VFD  it will automatically ramp up the motor to full speed?

Or does it mean,the frequemcy will be in the range of 5 to 60. 5 ( the current factory default setting of 5) to 60 Hz - adjustable with the pot as I need?

Going out to the shop now to look for the settings you suggested.

Thanks
Glenn


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## mksj (Oct 27, 2017)

Hi Glenn

If you set the speed to 60.00 Hz, it replaces the 5.00 Hz setting, yes it will ramp up to 60Hz when you hit run.. When you turn it on it will ramp up to 60Hz over the acceleration time, and stop on the deceleration time. If you cahnge 00-05 to 1 then the speed pot on the panel will be variable from the minimum to the maximum Hz values you enter. So by default, this would be 0-60Hz or 0-100%. It is also possible to set the minimum to say 30Hz and the maximum to 80 Hz, and in that case the speed pot would adjust between these ranges. Max. Frequency is set with 01-02, min. Frequency with 01-08.


Mark


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## CluelessNewB (Oct 27, 2017)

Make sure you don't exceed the maximum RPM that the grinding wheels are rated for.


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## Glenn Brooks (Oct 28, 2017)

Mark, I set all the parameters to the values you suggested, and Wa-la! Like magic, the grinder turned up to full speed.  runs sweet! Actually, I didn't need to change the 5 Hz to 60. Somehow that corrected itself after I punched in the motor values.

Clueless: the motor is running at 1800 rpm, and the wheels are rated for much higher, so good to go there

thank you!

Glenn


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## Glenn Brooks (Nov 2, 2017)

Hi all, one more question - about installing a simple remote on/off switch.  I ordered a two wire paddle on/off switch on line, but don't understand what function the 'com' port plays in activating the switch.

The TECO manual says to wire the 'on' side of the switch to the S1 port. Then wire the other side of the switch to "com".

What exactly is  this"com"?  It looks like  the negative side of a 12 v circuit. But why call it 'com'?

Thanks
Glenn


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