3 phase electrical question

[GHarman]

I have a 3HP, 3 phase, 230 volt motor on my lathe. I have been powering it with a static 1-3HP phase converter. The on/off cycles kill these converters. I was wondering if anyone out there knew how and could instruct me in how to hook up a 3Phase idler motor. What size motor for my application, etc. . Any help would be highly appreciated. GregH

 

[rbattelle]

Greg, you might consider a variable frequency drive unless you happen to already have a 3-phase idler motor available for free.

-Ryan

 

[GHarman]

Ryan, What is THAT!!! I am not familiar with "variable frequency drive" equipment. I dont have an idler motor, as yet and I'm on a tight budget. You'll have to do alot of 'splainin' to this old dog:-laf. GregH

 

[SRadke]

I'm no expert on the subject but I think he refers to a variable speed drive, or possibly a soft start.

 

[rbattelle]

A variable frequency drive is also called an "inverter. " Simply put, it converts your 240v AC line voltage to high voltage DC, then high-speed switches it to 3-phase output power. Very clean, very efficient, and remarkably affordable, depending on what you were planning on spending to get a 3-phase idler motor.



Here's the one I have (except I have the 1. 5 hp version):

Driveswarehouse



And here's one explanation of how they can be wired:

Wiring a VFD



You'll need to first determine whether you can get your idler motor for less than $255. If you can, then we can talk about wiring that up to generate 3-phase power. If you can't, then getting the VFD is likely a good choice. I know you're good with electricity, so I wouldn't expect you to have too many problems learning to wire and operate a VFD.



-Ryan

 

[p-Bar]

I have used VFD's for years to run my cabinet shop i use a 15hp unit leave it on and have multiple machines hooked up to it and they are very efficient those static and motor units lose you 1/3 of your hp . Go on ebay and punch in VFD just be sure it is advertised as single to 3 phase . You do have to buy a bit larger unit though because of the single to 3 phase conversion.

 

[GHarman]

Old Dog, New Tricks!!!!

Thanks a bunch Gentlemen!!!!! This new technology done passed me up, many moons ago!! "I dont need no stinkin idler motor"! BUT! I got a Buzz Box and need to replace it with one of these VFD units. Sizing it correctly, purchase and installing are the obvious steps. I will have to put some money together. This will take a few months. I really appreciate the information. I now have a direction that makes sense! GregH

 

[p-Bar]

Greg just remembered you need to go 30% oversize when converting single to 3 phase . The unit I bought was a ACTECH Lenze-ACTech Frequency Inverters good stuff application engineer to help you too. Made in America

 

[rbattelle]

Greg just remembered you need to go 30% oversize when converting single to 3 phase .

I'm not familiar with this rule, but I don't dispute you.

I sized mine according to the motor's FLA specification. Turned out I needed a 1. 5hp VFD to drive the particular flavor 1hp motor I have.

-Ryan

 

[p-Bar]

I'm not familiar with this rule, but I don't dispute you.



I sized mine according to the motor's FLA specification. Turned out I needed a 1. 5hp VFD to drive the particular flavor 1hp motor I have.



-Ryan

Just came to me that the engineer told me that when we were figuring configuration. Again only when converting single to 3 phase

 

[GHarman]

p-bar, I checked your link and it looks like this unit with the integral disconnect. This is the largest unit available in its class.

Lenze-ACTech SMVector [Integral Disconnect]



Ryan, I checked your link and this is probably in the ball park? I just need to do more research on this. I'm plumb wore out. Just got done with my taxes

I'll read more after I get this kink out of my neck:-laf! Thanks a BUNCH!!! GregH

 

[rbattelle]

Greg, that one might work, but remember you need to have 1-phase input. The site you linked says they only go up to 3hp with 1-phase input, but you need to consider what p-bar said about 30% oversize and/or what I said about checking the FLA spec on your motor.

Maybe tell us what your motor data plate says and we can be of more help.

-Ryan

 

[GHarman]

Ryan, Thanks! When I get over to the shop, I'll crawl down there and see whats on the motor plate. Wont be till next week, some time. The input is 230V, single phase. Dont remember what the amps are. I'll check the breaker panel, also! GregH

 

[p-Bar]

Greg all those VFD have a "soft start" so when you turn on the actual VFD it doesn't power on your appliance till you flip on the low power toggle switch you wire in to the terminal strip on the VFD. Since I am running multiple machines I have run 3 phase out to a 3 phase sub panel .

 

[seafish]

I have a 20Hp rotary converter tied into a 3 phase distrubution panel in my shop.

I then have separate circuits for each machine.

The largest draw is a 4 head planer/moulder with a separate feed motor that totals almost 18 hp when running.
The other loads (radial arm saw, planer) are no more ten 5 hp each.

I have never heard of this VFD technology.

Are there efficiency or other advantages to it over the rotary converters ??

 

[p-Bar]

I have a 20Hp rotary converter tied into a 3 phase distrubution panel in my shop.



I then have separate circuits for each machine.



The largest draw is a 4 head planer/moulder with a separate feed motor that totals almost 18 hp when running.

The other loads (radial arm saw, planer) are no more ten 5 hp each.



I have never heard of this VFD technology.



Are there efficiency or other advantages to it over the rotary converters ??

very efficient rotarys you loose about 20-30% though the manufacturers tell you different plus VFD's are true 3 phase 120 degree rotarys are trying to shove that third leg into the 180 degree single and they are pumping up that third leg with about 160vac to compensate . I am doing the same with a 3 phase sub panel

 

[seafish]

But from the previous posts, it seems that you have to oversize the VFD by about the same, approximately 30%, so how is that any different ??

I never knew that about rotary converters compensating the 3rd leg...
If I test the voltage at each leg against ground , will the difference show up ??

I'll check in the next couple days !!

 

[p-Bar]

But from the previous posts, it seems that you have to oversize the VFD by about the same, approximately 30%, so how is that any different ??



I never knew that about rotary converters compensating the 3rd leg...

If I test the voltage at each leg against ground , will the difference show up ??



I'll check in the next couple days !!

That is a recommendation of the manufacturer due to not inputting 3 phase doesn't mean that you lose efficiency on the output side. Yes each leg to ground curious to see what you have. Are you 208 or 220/240 at the panel?

 

[SMorneau]

VFD's are great and I would go that way if I did not already have a large rotary convertor. If I had a static and wanted to get by cheaper I would look for a 3 phase idler motor, they go for scrap prices around here.

 

[CKelley1]

yes, you do not loose 30% of your horsepower like you do with the static or rotophase converters and you can vary the speed of the motors, this is really nice on things like mills, lathes or drill presses