Yet more VFD questions... Belt sander

[Carl Beckett]

A lot of you advocate VFD to run 3 phase equipment. I have a Jet 7.5hp belt sander (1632, same as powermatic 1632) that I normally run off a RPC (rated at 10hp). I am setting this up in a new space and deciding on whether to keep with the RPC or convert the machine to VFD after which I can run it off single phase wherever I might be in the future.

I hear how cheap VFD's are, and they 'are', but I am trying to estimate an all in cost and have a couple decisions some of you can help with.

First - what size? The sander is rated at 7.5hp and a 10hp (7.5kw) vfd says it needs 35 amps. I might be willing to run it at a derated 5hp and pull 10awg wire since the rest of my shop is on 30A outlets. There is a convenience to that, but I give up some capacity of the sander (cant say I have ever tripped it, but wide belts take power)

Going from 10hp VFD to 15hp VFD jumps the price. And then I need a dedicated circuit and breaker. Doable without 'that' much work in the current setup. So this keeps the sander rating and seems worthwhile, but now limits choices and increases investment.

Then I need a second VFD to run the belt. This one is 1/4hp. I could swap the motor but currently the sander is a fixed feed speed, so this is where variable speed would really help to be able to control the belt speed. Having the same drive brand and enclosure for both would be a cleaner upgrade.

I like the idea of mounting the drive inside the cabinet (believe there is plenty of space for this), and panel mounting the controls. Some do this. I do not feel the need for vector drive on the sander since its not obvious why I would want to slow the sanding belt, only the feed motor.

Some suggest to stay away from the Chinese imports. This bumps price considerably. (I need to buy two drives)

Something like this gets me to 10hp at a reasonable cost: https://www.amazon.com/HKS-Variable-...67&sr=8-7&th=1

But some of the US brands stop at 5hp for single phase input. So there are fewer options if going to 10hp with a single phase input. And going to 15hp vfd pushes price even higher. I think I am missing something to consider here...

So its not quite as simple nor as cheap as it might be on other machines - at least at first glance. Educate me!

Any insights?

[Kevin Jenness]

Why change from the rotary converter you use now? Seems like an unnecessary expense. Using an undersized vfd and having less power available on that machine seems self-defeating. If it were me I would keep the 10 hp rpc and add an inexpensive small 3 phase input vfd to control the feed motor,

[Carl Beckett]

Why change from the rotary converter you use now? Seems like an unnecessary expense. Using an undersized vfd and having less power available on that machine seems self-defeating. If it were me I would keep the 10 hp rpc and add an inexpensive small 3 phase input vfd to control the feed motor,

A fair question.

Wiring/code requirements of installing a RPC.

Future flexibility to simply plug it into standard single phase outlets and not have to jump through all the code requirements at each install, since I am likely to move again. (did I mention meeting electrical code? )

The variable feed rate feature - or after some more reading some do turn the belt speed lower for woods that are prone to burning. But as you say, I could get variable belt drive with just a smaller add (likely worthwhile upgrade independent of the main motor wiring)

[Kevin Jenness]

The variable feed rate feature - or after some more reading some do turn the belt speed lower for woods that are prone to burning.

Actually, increasing the feed speed (plus sharp abrasive and lighter cuts) is better.

[Jim Bixel]

Take a look at https://www.phaseperfect.com/enterpr...-volt/pte007r/

I have one of there older larger units and have been running my whole shop off it for about 10 years now. I live real rural and loose my power all the time with a lot of voltage spikes and I have never had a issue with there unit even with all this abuse.

[Carl Beckett]

Take a look at https://www.phaseperfect.com/enterpr...-volt/pte007r/

I have one of there older larger units and have been running my whole shop off it for about 10 years now. I live real rural and loose my power all the time with a lot of voltage spikes and I have never had a issue with there unit even with all this abuse.

These are great units with great reputation. (more $$ than I was hoping to spend) My RPC was $500 used. I could always swap a motor and turn the machine into single phase.

When push comes to shove I prefer to spend money on the equipment instead of the wiring, since I will pull the wiring out when I leave.

Have a couple new ideas. Its going to come down to what the inspector wants. (but in general, most RPC installs I see do not meet code for one reason or another)

[Bobby Robbinett]

I looked into running a wide belt off of a VFD once. I was told that there is a guy named Jack Forsberg that is the master at making custom VFD’s for applications like this. I have a buddy that had a 10hp wide belt and to get it setup with Jacks’s VFD’s was close to $2,000. Once he told me that I just bought a 100hp panel from American Rotary and picked up a used 100hp motor and now I can run what ever.

[Mike Leiferman]

Carl,
Send me a note if you try a VFD. I would like to go that route with my 7.5 hp 3p saw motor. The cost of the drives ranges from about $170 to $1800 - and I have no idea why the variation other than country of origin.
Mike Leiferman
leiferman@gmail.com

[Carl Beckett]

Carl,
Send me a note if you try a VFD. I would like to go that route with my 7.5 hp 3p saw motor. The cost of the drives ranges from about $170 to $1800 - and I have no idea why the variation other than country of origin.
Mike Leiferman
leiferman@gmail.com

Happy to. I havent pulled the trigger on a VFD just yet. If I can get the RPC installed and passed that will be my easiest/cheapest path. More to come.

[Michael Schuch]

A lot of you advocate VFD to run 3 phase equipment. I have a Jet 7.5hp belt sander (1632, same as powermatic 1632) that I normally run off a RPC (rated at 10hp). I am setting this up in a new space and deciding on whether to keep with the RPC or convert the machine to VFD after which I can run it off single phase wherever I might be in the future.

I hear how cheap VFD's are, and they 'are', but I am trying to estimate an all in cost and have a couple decisions some of you can help with.

First - what size? The sander is rated at 7.5hp and a 10hp (7.5kw) vfd says it needs 35 amps. I might be willing to run it at a derated 5hp and pull 10awg wire since the rest of my shop is on 30A outlets. There is a convenience to that, but I give up some capacity of the sander (cant say I have ever tripped it, but wide belts take power)

I would use a 10hp (7.5kw) VFD on a 30A outlet. Your 7.5hp motor should never be able to draw the full rated 35 amps through the VFD. If it does the 30amp breaker in the breaker box will pop.

Going from 10hp VFD to 15hp VFD jumps the price. And then I need a dedicated circuit and breaker. Doable without 'that' much work in the current setup. So this keeps the sander rating and seems worthwhile, but now limits choices and increases investment.

I would stick to the 10hp VFD and skip the 15hp VFD. A 10hp should give you plenty of headroom for your 7.5hp motor even when it is under a high load.

Then I need a second VFD to run the belt. This one is 1/4hp. I could swap the motor but currently the sander is a fixed feed speed, so this is where variable speed would really help to be able to control the belt speed. Having the same drive brand and enclosure for both would be a cleaner upgrade.

I go for name brand VFD's when I am able to but go with Chinese VFD's when a name brand isn't practical. I own Fuji, Teco, Allen Bradley, Toshiba and Chinese VFD's. For simply running a 3ph motor with speed control there really isn't a lot of difference. For running a 3ph metal lathe with speed control, forward/reverse, jog fwd/rev, braking, emergency stop with fast braking, etc. the documentation and more advanced capabilities are worth buying a name brand VFD to me. For simple phase conversion and speed control I would go Chinese.

I like the idea of mounting the drive inside the cabinet (believe there is plenty of space for this), and panel mounting the controls. Some do this. I do not feel the need for vector drive on the sander since its not obvious why I would want to slow the sanding belt, only the feed motor.

I prefer to mount my drives in a separate water tight electrical box (EBAY! Look at used ones to) to keep all the saw dust out of the VFD. I have gone so far as to put a fan in the box I run a large VFD in with a good filter to keep air circulating and the VFD cool. I would suggest this for your application. You can easily run the controls out of the box and mount them on the control sander of your sander. Use some connectors on the box so you can easily detach the controls and work on the ox if you need to.

Some suggest to stay away from the Chinese imports. This bumps price considerably. (I need to buy two drives)

Chinese will get the job done!

Something like this gets me to 10hp at a reasonable cost: https://www.amazon.com/HKS-Variable-...67&sr=8-7&th=1

Yes, I would purchase this VFD that you linked to.

But some of the US brands stop at 5hp for single phase input. So there are fewer options if going to 10hp with a single phase input. And going to 15hp vfd pushes price even higher. I think I am missing something to consider here...

So its not quite as simple nor as cheap as it might be on other machines - at least at first glance. Educate me!

Any insights?

Are you a production shop or a hobby shop? A Chinese VFD should last for years without issue. You will probably be down for a week on the chance the VFD dies and you have to order a replacement. If your VFD dies it will probably be due to dust build up on the VFD causing it to overheat. If you are a production shop I would recommend sticking with the the tried and proven RPC you already own because your income would probably be seriously affected by down time.

[Carl Beckett]

Thank you Michael, for such detailed insight and recommendations!!

I will know by tomorrow which direction this is headed.

[Bill Dufour]

Be careful about amp requirements. A VFD will almost eliminate the inrush start current problems but.
Example for a 10amp three phase motor supply from a single phase line. Note a VFD will have some small percentage of loss internally.
Single phase to 3 phase power calculation input requirement = The square root of 3 (1.732) x 10 amps
= 1.732 x 10 amps
Bill D
= 17.32 Amps

[Carl Beckett]

The inspector says: need a breaker on the output of the RPC. So that means a box and a 3 phase breaker.

Its not obvious they make single breaker boxes, and the larger boxes seem quite large and $.

More homework.

It is down to adding the breaker or starting over and running single phase all the way to the machine and putting on the VFD (which very well could be more straight forward...)

All ears on how others have done it.

[Michael Schuch]

The inspector says: need a breaker on the output of the RPC. So that means a box and a 3 phase breaker.

Its not obvious they make single breaker boxes, and the larger boxes seem quite large and $.

More homework.

It is down to adding the breaker or starting over and running single phase all the way to the machine and putting on the VFD (which very well could be more straight forward...)

All ears on how others have done it.

This is one area where ebay still really shines! Surplus electrical supplies are a tiny fraction of buying new.

https://www.ebay.com/itm/22449314272...8AAOSwX4dgwnPo

https://www.ebay.com/itm/35342258146...YAAOSw9vdgUXoH

https://www.ebay.com/sch/i.html?_fro...r+box&_sacat=0

https://www.ebay.com/itm/27225505934...4AAOSwuU9dI6X~

https://www.ebay.com/itm/17346330689...UAAOSwL7dbbejS

https://www.ebay.com/itm/26527691121...AAAOSw~KphH8iV

https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=12


My approach was no inspector. I put 40amp 1ph receptacle on the wall right below the breaker box and wired it in with a 40amp breaker. Then I put two 30 amp 3ph receptacles in my RPC control box, one for the idler motor and one for the driven machine. I never wired my shop for 3ph which is why I run VFD's for almost all machines.

PICT8059.JPG

PICT8057.JPG

[Kevin Jenness]

I found a used distribution panel with breakers at an online electrical supply website for low $. That plus a used 10 hp 3 phase motor a starter (basically a switched static converter) and some cable set me back about $600. I run a sliding table saw and a planer from it. I also have several machines powered by vfds which benefit from speed control (exhaust fan, edge sander and lathe) and a slot mortiser running off a static converter.