VFD seems too good to be true

[kb58]

That's not true at all. I'm not looking at the low end, I just did a Google search, and this is what came up. I don't know which brands are the best-- I did a Google search for "VFD Best Brands", and all I got are those stupid web pages where people put up generic marketing information and an affiliate link to Amazon, so they make money when you make a purchase. If there are high quality brands that I should know about, please tell me. Even better, if there's a high end brand that does what this one claimed to do, I'd really appreciate learning about it. But although there's a person in this thread saying he's using this model to do what it says it does, the consensus is that this is a kludge that's not likely to work out the way I want in the long run, so barring further information, I'll just need to wait until I can get the new panel installed and wiring done.

Okay, fair enough, but don't use low cost as a reason to buy.

A VFD that uses single-phase input 110V is unusual, and it's very unusual that it outputs 220V. Nearly all are designed to accept 220V single-phase and output 220V 3-phase. Assuming that you have 220V available (drier vent?), I highly recommend buying a 220V 3-phase machine and using a VFD, but only if you need variable speed of course.

 

[hman]

Regarding current draw ... one of the questions asked was about a manual and the current draw. The seller responded that you need 20 amps. Others have pointed out that it would probably take more current than that, and it sounds a bit low to me as well. Also note that one of the first bullet points in the description says "The vfd only supports light load motor." Strange to call a 3 HP motor "light load!" Personally, I'd tend to avoid this VFD.

@andrewgr - I think spending the $$$$ to get your panel upgraded would be a very good investment. From your description, it sounds like a fire waiting for a time to happen. Stay safe!

 

[metric_taper]

Isn't 2.2 Kw at 220 V 10 A

At 110VAC, 2.2Kw is 20amps, but that assumes this is 100% efficient. They use a voltage double circuit, capacitors and steering diodes to pump the voltage to the DC input. This is over 311VDC some losses, but closer to 340VDC with 240VAC as that is the distribution standard. 110/220 are archaic.
My experience with Huangyang VFD, it failed in my shop on power up test. Very loud bang, which I assume was one of the DC filter capacitors. I had to wait for a replacement from China. But I was unimpressed with the quality. Also this is not a sensorless vector drive, so it will not do high torque low RPM motor operation. But I'm guessing they have improved on their component quality by now. $260 is pricey for this brand.
I'm with the other posters that this idea of 120VAC input should be canned. However for lower wattage, this unit may be OK.
When I go to the Precision Matthews Lathe and Mill web site, I have no clue what models the OP is looking at.
My experience on large lathe with 7.5HP motor, I use a 10HP VFD to drive it. I will never use the full rated HP of this lathe, so I'm not worried about derating the normal 2:1, mainly for the input diode current limit using single phase source.

 

[andrewgr]

Okay, fair enough, but don't use low cost as a reason to buy.

A VFD that uses single-phase input 110V is unusual, and it's very unusual that it outputs 220V. Nearly all are designed to accept 220V single-phase and output 220V 3-phase. Assuming that you have 220V available (drier vent?), I highly recommend buying a 220V 3-phase machine and using a VFD, but only if you need variable speed of course.

Could you expand on the last sentence? I was under the impression that even if I have a 220 feed, I'd still need a VFD to go from one phase to three phase. I'm not sure what you mean by "if you need variable speed".

 

[Cooter Brown]

Screw the VFD..... If you have 220v 1PH all you need to do is get a static phase converter for like $50....... Its just a relay and a couple start capacitors.... But they work great....

HD 3 - 5 HP Static Phase Converter Mill Drill Saw MADE IN USA Single to three | eBay

3 to 5 HP STATIC PHASE CONVERTER. Bench grinder. Chop saw (1HP & under). Thickness planer. Product Line: STATIC WAVE. Table saw (2HP & under) Band saw (belt drive). Drill press (2HP & under). Radial arm saw.

www.ebay.com

I have this one and was using in for a 3hp 3ph motor on an air compressor before I got the new shop.....

 

[andrewgr]

Screw the VFD..... If you have 220v 1PH all you need to do is get a static phase converter for like $50....... Its just a relay and a couple start capacitors.... But they work great....

HD 3 - 5 HP Static Phase Converter Mill Drill Saw MADE IN USA Single to three | eBay

3 to 5 HP STATIC PHASE CONVERTER. Bench grinder. Chop saw (1HP & under). Thickness planer. Product Line: STATIC WAVE. Table saw (2HP & under) Band saw (belt drive). Drill press (2HP & under). Radial arm saw.

www.ebay.com

I have this one and was using in for a 3hp 3ph motor on an air compressor before I got the new shop.....

I see. Thanks!!!

I'm used to being competent at the things I do. Nearing retirement, I'm trying some new things-- failing doesn't seem as awful to me as it used to. But it sure is humbling to be a complete novice surrounded by professionals and near-professionals!

 

[hman]

EVERYBODY here started out as a novice, and ALL of us are novices in innumerable fields.

There are several ways to get to 3 phase - static phase converter, rotary phase converter, and VFD are the most popular. There are advantages and disadvantages to each. The advantage of a VFD is in the "V" of the abbreeviation - variable. It allows you to change the speed of a mill or lathe with just the turn of a dial. If all you need is a motor running at a the rated (single) speed, then you should consider either a static or rotary phase converter. They're generally less expensive (as @Cooter Brown has pointed out).

 

[mksj]

I think it might be helpful to indicate what you want to power and what your needs are. A static converter works in some applications but you loose 1/3rd of your Hp. It can also cause some surface finish issues because it is not true 3 phase, and you also need to know which is the generated 3rd leg/phase and this should not be connected to transformers and electronics. A VFD can also be a bit more complicated to install and is made to power the motor, not operate the machine. You use low voltage input connection on the VFD to tell it what you want to do, not the machine controls like contactors and so forth. VFD's come in many variants, until several years ago they operated off of voltages of 200V and higher, some of the newer lower Hp models now have voltage doublers which allows them to operate off of 120VAC. The maximum size I have seen is 1.5Hp single phase 120VAC VFDs that will output 3 phase 230VAC. The limitation is typically single phase circuit is 20A, and that limits the maximum output power. When a manufacture talks about light duty, it may mean a 3 Hp motor that is delivering 1.5-2Hp worth of output/work. So may be fine for spinning a saw blade, but start cutting hard and it will stall. Same is true of a static converter.

The largest single phase 240VAC input VFD's usually is 3 Hp and very few go to 5 Hp, a VFD designed for 3 phase input needs to be derated usually by a factor of 2 to run on single phase. So if you wanted to run a 5 Hp motor, you would need a 10 Hp 3 phase input VFD and you could run it off of single phase. This is because of how the power is delivered to the input, and what limits single phase input VFD's.

So a lot of the cheap eBay and Amazon VFD's may have ratings, but they do not specify the operating conditions that is clear to others. They may work for some people, others not. You can spend a little more for say Teco, Hitachi, Fuji VFDs that are much clearer about their ratings, all of them can be a bit challenging at first to understand. There are some great on-line videos that go through how to connect and program something like the Teco L510, and other VFD's worth a look.

If you have a marginal electrical panel, the last thing you want to do is overload it and possibly have a fire. Better to be safe and do it right the first time, I have seen some scary electrical work and it can be very dangerous.

 

[andrewgr]

I think it might be helpful to indicate what you want to power and what your needs are.

Let me say, "Thank you" again for your patience and help.

I'm planning on a lathe: a Precision Mathews PM-1340GT, which is 2 HP and comes either 1 phase or 3 phase.
I'm also looking at a mill, but it looks like it runs on 110 20 amp; even if I got a different model, I'm sure it wouldn't draw more than the lathe.

I'm just a pure hobbyist. I won't be making production runs of anything. My initial use case is making lightsaber hilts, lightsaber stands, and tools for my (small) workshop. I know that it's more lathe than I need, but I'm in my 50s, I'm aiming to retire in 5 years, and I can afford the extra $1K or whatever it is more than a model that's a step or two down. Also, I don't know exactly where this hobby will take me-- it seems reasonable to get the best my limited space and budget will accommodate.

 

[metric_taper]

Could you expand on the last sentence? I was under the impression that even if I have a 220 feed, I'd still need a VFD to go from one phase to three phase. I'm not sure what you mean by "if you need variable speed".

That is one of the real good reasons to use a VFD. This stands for Variable Frequency Drive. VSD is the same thing, this term used more in Europe, for variable speed drive. These work by taking your AC input, and rectifying it to DC, then chopping it up to AC but at a much higher frequency pulse rate, as it's a duty cycle. It is all controlled with special purpose microprocessors. I have removed all single phase motors from all my metal machining equipment. And it's for this purpose. I never change the belts on any of my machines. I get better then the original spindle speed range. I have two lathes, one with a 2HP motor (it had a 1HP single phase as purchased a 10x24 bench top), and a 18x40 lathe with a 7.5HP motor. That has a gear head, and I do change them for the speed ranges. The only time I mess with the VFD speed is for real slow single point threading, or driving a tap or die. A drill press with a 1HP (belt drive), a vertical mill with a 2HP motor (belt drive), and a horizontal mill with a 3HP motor (this has a Lima conversion system as it was originally an overhead lineshaft driven machine).
Looking up your lathe; Precision Mathews PM-1340GT; You most likely will not get the real benefits of a VFD as it's a gear head lathe. Nice specifications, D1-4 spindle nose. MT5 spindle taper, 1-9/16" spindle through hole. Made in Taiwan. I think this is a great lathe, for a life time.
It is a bench style lathe. The only issue I had with my much smaller lathe, was heavy cuts, like parting operations. It would dance on the floor, mounted on a sheet metal lathe stand. My fix was to get a 2" piece of steel, as large as the base of the lathe, mark the bolt down hole locations and drill and tap this base. This was placed under the chip pan and the sheet metal base was bolted from below to the 2" steel plate. That made the lathe stop flexing. It would go into harmonic oscillation and 'dance' on the floor. For reference I got this lathe in 1977 Jet brand.