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Looking for economical single phase to three phase VFD

thomj

Aluminum
Joined
May 18, 2007
Location
michigan
Does anyone know where I can find a single phase to three phase 7.5 HP VFD? One that will last for a machine tool application? I was thinking somewhere around $600 but I think I am just not being realistic. Looking at adding another machine and trying to figure out how much this will cost. I do have a phase converter that isn't hooked up. I can use that but like the idea of having the variable speed control of a VFD. All of my other three phase machines are on VFD's

Thanks ahead of time. I will respond when I can.

Thom J
 
All my machines run on Mitsubishi VFD's. Biggest one is a 10HP one on my lathe. It is a 3 phase in and out but works fine with single phase input. It was about $450 around 5 years ago.
 
All my machines run on Mitsubishi VFD's. Biggest one is a 10HP one on my lathe. It is a 3 phase in and out but works fine with single phase input. It was about $450 around 5 years ago.

Really? Do you by chance know the model number? If not to much trouble. I have used AC Tech in the past. But to much money for what I want to do. You know,every penny I can save is a penny earned....
 
I get nervous buying something like that used. I figured it was a long shot. but thought I should ask in case someone here knew something more than what I have found...

Thanks,
Thom J
 
The Mitsubishi 10HP on my 5HP lathe is a model FR-D720-318-NA. If using a three phase input VFD with only single phase available you need to go up one size bigger and Mitsubishi don't make any single phase input models bigger than 3HP. I also have a remote control/display on the lathe to vary the speed without needing to go over to the VFD. Doing some price checking on it this morning the price is all over the place depending on the vendor.
 
The Mitsubishi 10HP on my 5HP lathe is a model FR-D720-318-NA. If using a three phase input VFD with only single phase available you need to go up one size bigger and Mitsubishi don't make any single phase input models bigger than 3HP. I also have a remote control/display on the lathe to vary the speed without needing to go over to the VFD. Doing some price checking on it this morning the price is all over the place depending on the vendor.

Ok. Thanks. I have heard the Mitsubishi drive are good. But I am far from a expert on this.

thank You very much!
 
Not one size up, you need to at least DOUBLE the size of the VFD if feeding it with single phase. So for a 7-1/2HP motor, you need a 15HP VFD. $600 is doable for that though.

Teco and Hitachi are good products in that price range new. Most everything else will have to be used to get down there and there are some risks to buying used VFDs for the uninitiated. I don't personally like AutomationDirect (I call them AutomationDestruct) but others are OK with them. They don't actually make their drives, they are brand-label deals and most of them come from a Taiwanese company called Delta. Delta makes good drives and cheap drives but they are not the same. I don't know which one becomes the AD "Durapulse", but my experiences with them point to the cheap version. Still, AD drives are still better than the super cheap no-name brands being sold on Fleabay and Amazon. THOSE are one you should steer clear of. Most have no name, or use a name that is officially banned from discussion here. Just stick to major name brands you have heard of and you should be fine.
 
I'm a peon compared to some of the expertise that is already participating in this discussion - but do I remember (I think?) from other discussions here that larger drives (generally intended for only 3ph input) sometimes (often?) have a function that if one of the three input phases is lost, then the drive shuts down, to protect itself if it is in its usual application of operating a motor at the drive's full nameplate capacity? Perhaps that can be disabled, but I'd want to verify that it can be disabled before investing in a particular make/model of drive. . . .
 
I'm a peon compared to some of the expertise that is already participating in this discussion - but do I remember (I think?) from other discussions here that larger drives (generally intended for only 3ph input) sometimes (often?) have a function that if one of the three input phases is lost, then the drive shuts down, to protect itself if it is in its usual application of operating a motor at the drive's full nameplate capacity? Perhaps that can be disabled, but I'd want to verify that it can be disabled before investing in a particular make/model of drive. . . .
Yest that is true. It used to be more common that it is now, most of the VFD mfrs realized that not giving users the ability to disable the phase loss trip (or ignore phase loss altogether and just look at the DC bus ripple) mostly just results in limiting your sales. So as mfrs redesign they products that issue has been fading.
 
And at 7 1/2 hp it starts becoming attractive to build your own front end and adapt it to a 7 1/2 hp drive. Only the rectifier section (diode bridge and capacitors) are different between a single phase input and 3 phase input.

Last week I was running a trial on a 1 hp 240 volt unloaded motor. One motor lead fell off and the drive was tripping on DC Link Undervoltage when it got to around 45 hz. The tech support engineer said it was a DC Link Undervoltage fault because I was single phasing the drive and it was designed for 3 phase input - I did not like that answer - drive output rating is 16 amps and drive never went over 5 amps output. By the time my conversation with the VP of Drives was done, they wanted to send me 2 drives to play with and give them feedback on how I like them. Should have the drives this week. One is a single phase input and one is a 3 phase input.
 








 
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