Three Phase 50HP Motor Control

[powerplay]

I have been asked to connect a three phase 480 volt 50HP Motor for a Sawmill. I have requested pricing from three Electrical Suppliers, but have gotten a price from one for an Variable frequency Drive... he said it is the economical way to get it done.... any advice or feedback?

 

[templdl]

I have been asked to connect a three phase 480 volt 50HP Motor for a Sawmill. I have requested pricing from three Electrical Suppliers, but have gotten a price from one for an Variable frequency Drive... he said it is the economical way to get it done.... any advice or feedback?

Economical, as comp as red to what what? Certainly a full voltage non reversing starter would be less expensive. If starting is an issue, which you didn't state that it was, a soft starter should be considered.
But if there are no starting issues an across the line full voltage starter would coast less and do the job just fine.

 

[Besoeker]

I have been asked to connect a three phase 480 volt 50HP Motor for a Sawmill. I have requested pricing from three Electrical Suppliers, but have gotten a price from one for an Variable frequency Drive... he said it is the economical way to get it done.... any advice or feedback?

I think templdl got it just right. There is no way a VFD solution could be comparable with an across the line starter. Economical? No way. Economical with the truth? Very probably.
Unless there are compelling reasons to go VFD, walk away from it.

 

[powerplay]

Economical, as comp as red to what what? Certainly a full voltage non reversing starter would be less expensive. If starting is an issue, which you didn't state that it was, a soft starter should be considered.
But if there are no starting issues an across the line full voltage starter would coast less and do the job just fine.

...sounds like I was being misinformed..... the salesrep said it is the cheap way to do it....

 

[Besoeker]

...sounds like I was being misinformed..... the salesrep said it is the cheap way to do it....

Get him to provide a written quotation for an across the line starter and an alternative VSD.
Money talks. Bullsh1t walks.

 

[jusme123]

I did not realize those VFD's where that expensive, $3700?

 

[kwired]

Economical would mean slowing down the driven load during certain times may save on energy costs. Usually an application for fans and pumps where there are times when low flow can be tolerated but yet you don't want to completely shut down.

Controller costs alone - the drive should cost more then a simple across the line controller.

 

[ptonsparky]

I can get a pump panel for 1/3 the cost of a VFD, connect 8 wires, set the overloads and walk away.

 

[Besoeker]

I did not realize those VFD's where that expensive, $3700?

Does seem to be expensive. I'd expect to pay about $2.5k for a 37kW drive.

 

[petersonra]

Does seem to be expensive. I'd expect to pay about $2.5k for a 37kW drive.

The thing is if you ask for a quote and do not know what is available you will never get a decent price. Most people just do not know what this stuff can be had for so they pay through the nose when they buy.

I would expect that a 25Hp drive at 480V can be acquired for under $1000 if you know where to look and how to ask for the price.

here is one that is $1170 and I did not even look that hard.

http://www.driveswarehouse.com/s-77...80-480-10&select3=&select4=&select5=&select6=

Generally, online prices are somewhat higher than what you can get them for if you know what to say and who to ask, but this shows what can be gotten and rough pricing.

I would expect under $2000 for a 50 HP unit.

 

[ptonsparky]

The thing is if you ask for a quote and do not know what is available you will never get a decent price. Most people just do not know what this stuff can be had for so they pay through the nose when they buy.

I would expect that a 25Hp drive at 480V can be acquired for under $1000 if you know where to look and how to ask for the price.

here is one that is $1170 and I did not even look that hard.

http://www.driveswarehouse.com/s-77...80-480-10&select3=&select4=&select5=&select6=

Generally, online prices are somewhat higher than what you can get them for if you know what to say and who to ask, but this shows what can be gotten and rough pricing.

I would expect under $2000 for a 50 HP unit.

It will help If you buy more than a few a year. For me, I have on hand more VFDs than the 3 closest suppliers only because I have more than 0. (2) They can be competitive with Online, but barely and if I want it in a couple days with no freight charges, forget it.

 

[Besoeker]

The thing is if you ask for a quote and do not know what is available you will never get a decent price. Most people just do not know what this stuff can be had for so they pay through the nose when they buy.

I think another aspect is that not every in our field is altogether familiar with what features a drive can include, those that can be excluded for the specific application, or don't know the right questions to ask. And that can make a substantial difference to price.
As can asking what discounts are available.

And, for something of that value, I'd want the quotation in writing detailing what was being offered.

 

[don_resqcapt19]

Do you have 3 phase power available?....if not the supplier may be correct.

 

[ptonsparky]

Do you have 3 phase power available?....if not the supplier may be correct.

That is a thought, but now that moves it up to a 100 HP VFD. Ouch.

 

[Jraef]

If you don't need speed control, there is no way this is even remotely economical compared to an across-the-line starter or even a soft starter at 50HP. Buying a VFD when you don't need it is foolish. There are thousands more parts to fail and if you never change the speed, you are going to increase the operating cost, because the VFD loses about 3% of the energy it is controlling to heat. That supplier is a scam artist, or at best, an ignoramus. In either case, stay away.

If you CAN gain some sort of benefit from changing speed, that's a different matter altogether, but you didn't say what this is for, only that it is in a sawmill. That's too vague.

 

[Besoeker]

I have been asked to connect a three phase 480 volt 50HP Motor for a Sawmill. I have requested pricing from three Electrical Suppliers, but have gotten a price from one for an Variable frequency Drive... he said it is the economical way to get it done.... any advice or feedback?

Whats the 50hp motor driving?

 

[kwired]

Whats the 50hp motor driving?

Um, a sawmill





I know, you probably meant please be more specific about nature of the driven load.

 

[GoldDigger]

Perhaps a saw?

 

[Jraef]

Perhaps a saw?

Generally, changing speed on a saw is not a good idea. Saw blades are designed for a specific operating speed, as in how fast the cutting teeth move across the material. Changing that speed can result in poor performance and even dangerous consequences.

 

[GoldDigger]

Generally, changing speed on a saw is not a good idea. Saw blades are designed for a specific operating speed, as in how fast the cutting teeth move across the material. Changing that speed can result in poor performance and even dangerous consequences.

But a controlled starting ramp and active braking could both be advantages.
I agree that the feed motors would be even better candidates for VFD.
Which would likely be the largest motor?