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

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.
 
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
 
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 :)
 
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
 
Last edited:

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.
 
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

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
 
Last edited:
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
 
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
 
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
 
Last edited:
Back
Top