Electic motor advice

[Kent]

Currently building a 2x72" belt grinder Got all wheels turned up and plans in progress.
Now motors ....
I have a treadmill motor but it unshielded and as i know tge grinding dust will kill it too soon iam thinking of laying it to one side and buying a new one direct for purpose

A fb group i joined on these machines seem keen on 240 v dc with a vfd to alter speed. But thinking is it worth the cost and hassle (as i dont even pretend to be very clued up on electrickery).
How much more hassle and cost might this add over just buying a single speed 240v with the correct speed for my drive pulley to keep under the lower level max speed rating of the belts? Ie dc over ac with the vfd ontop ?
Best suppliers ?
Thoughts?
Obviously looking for full shielded type of motor

 

[Matrixx]

tricky question, A DC motor might be more expensive but the speed control will just be a DC voltage regulator which will be cheaper than a VFD drive, but the AC motor would be cheaper.

all depends how important speed control is for you.

 

[Kent]

tricky question, A DC motor might be more expensive but the speed control will just be a DC voltage regulator which will be cheaper than a VFD drive, but the AC motor would be cheaper.

all depends how important speed control is for you.

Whats the percentage difference likely to be though ?

 

[the snooper]

If you want different speeds you could always use a stepped pulley like pillar drills

 

[rikrobson]

What is you power requirement for the project?

a 3ph 1/2HP motor will be under £100 of ebay and a VFD will be less than £50

its not just varialble speed, that is a benefit of VFDs you can have a soft start as well as braked stopping to name a couple

 

[Anguz]

I might have something to interest you... fairly certain I have some motors with built in vsd... 240v ac input.. would be about 1hp at a guess, (can check)
Am intending to use one myself for the same thing

 

[Kent]

Waiting of a reply from a specialist motor firm and cost. Lets see obviously i have spindle and keyway requirements to fill etc

 

[brightspark]

no real need to have them run at different speeds just select the right grit belts. if you want to remove stuff fast just press on harder lighter for a slower cut

 

[vbottles]

Do you already have v pulleys? If not go the vfd route. The cost of pulleys will be more than halfway to buying the vfd.
I made a grinder a few years ago and LOVE how I can go really slow to scary fast. You can also run the motor up to 150% without risk of damage and faster for occasional use.
The one down side is the lower speeds do have a drop off of power. But when will you run at 20% power and hogg down on the belt.
Is also look to a larger motor. Belt grinders usually run 1hp per inch width of belt. Hence most grinders run 2hp/1.5kw.
If your building from scratch look at making one that can go horizontal. These look good for basic surface grinding or controlled grooving.
Andrew

 

[brightspark]

so a 6inch belt sander needs a 6hp motor I have a 6inch x 1meter belt sander and it has a 1hp motor fitted and a 4inch with a half hp and both are well capable of a good riving

 

[Kent]

Sorted found a link Going vfd three phase
https://dcknives.blogspot.com/p/grinder-motors.html?m=1

 

[Kent]

no real need to have them run at different speeds just select the right grit belts. if you want to remove stuff fast just press on harder lighter for a slower cut

Oh there is for my purposes.. Using synthetic handle mstrrials or wood but also very high wear factor high carbon steels and various belts And grits.

 

[Kent]

Do you already have v pulleys? If not go the vfd route. The cost of pulleys will be more than halfway to buying the vfd.
I made a grinder a few years ago and LOVE how I can go really slow to scary fast. You can also run the motor up to 150% without risk of damage and faster for occasional use.
The one down side is the lower speeds do have a drop off of power. But when will you run at 20% power and hogg down on the belt.
Is also look to a larger motor. Belt grinders usually run 1hp per inch width of belt. Hence most grinders run 2hp/1.5kw.
If your building from scratch look at making one that can go horizontal. These look good for basic surface grinding or controlled grooving.
Andrew

Thanks am going vfd three phase.. Swatted up some on the net. I freely admit its not my area but i found the low down and i could run 3-5 hp and have the speed + direction control got to be worth it, not doing this twice to get it right, its going to see a lot of action and time is money

 

[Luke]

Have a look at https://inverterdrive.com/

Pretty reasonable prices, and a proper company to deal with.

 

[vbottles]

Think that's the same company I bought my lady vfd from. Very helpful and have heard they will talk people through wiring up the vfd.
For background my first linisher was a commercial beast I bought off ebay for £50.
Worked great but s***t scary to use. Think it ran over 30 meters per second. It was great at hogging off material but it wanted to eat you if it could.
I built a 50x2000 grinder using a piece of i beam for the body. As its what I had to hand. Its the best tool I've made. It was also a huge leap in what I could make.
If I ever get to make another I'd look at a tw 90 for ideas.
http://www.traviswuertz.com
Andrew

 

[Kent]

Certainly going throgh a learning process here on this one

Using a VFD from single phase supply powering a two pole 3 phase motor there are issues with emergency stop fitting ?

 

[dai]

Certainly going throgh a learning process here on this one

Using a VFD from single phase supply powering a two pole 3 phase motor there are issues with emergency stop fitting ?

you can set the ramp up time and ramp down time
i just fitted a new 1 to my lathe and set the ramp down to 1 second so it stops quick

 

[Luke]

As long as the motor has a 230V winding (normally delta, i.e. a 230V/400V motor), the single phase 230V input, three phase 230V output is not an issue - there are plenty of suitable inverters.

There are a number of options for a proper E-stop;
- STO (Safe Torque Off) functionality - probably outside of the price range we're looking at.
- Contactors in the supply to the VSD. How many (1 or 2) and how they're controlled depends on how far you want to go - An industrial application would probably use a certified safety relay (Pilz being the ubiquitous brand - the 'Hoover' of safety relays).
- Non-safe quick ramp down of the drive. will provide the functionality, but not the performance to a safety standard.

Combinations of the above can be effective - a quick stop of the drive, followed by the contactor opening a few hundred milliseconds after the drive should have stopped is a valid approach.

Luke

 

[brightspark]

by the time you have decided to stop it with safety gear it has already skinned you alive and its 2 late

 

[Luke]

If you're just considering Cat 0 stops, yes, that could be the case.

Cat 1 stops, using Off3/quickstop/SS1 solve that issue, and you can still go on to provide safe isolation of energy.

On the basis that most of the discussions on here can involve significant inertia (lathe chuck and workpiece, etc.) I would go for a combination of the two - quick stop, followed by opening the contactor.