Question about putting VFD on a step pulley mill.

[ignator]

Interesting - - - thanks!

Any issues of EMI (or electro magnetic compatibility; EMC) are from long runs of wire between the VFD and motor, keep them less then 6ft/2meters long and you'll have zero issues of upset of any control wires used to remote the start stop speed. The manual has the requirements for the potentiometer (variable resistor) for remote speed control (Kohms and power rating). Just follow the manuals suggestions for the remote wiring.
Also NEVER put a switch between the VFD and motor, hard wire that. The reason is if you switch the motor while the VFD is running the motor, huge transient voltages can be created that blow up the transistors in the VFD, and at that point it's toast.
Also VFDs really are intended to be connected to one motor. They protect the motor from overload as that's a programable parameter in them, i.e. the motor HP and running current typically. So you can buy a much larger VFD, and program the motor size so it won't be overloaded. Running motors at very slow RPMs for long periods, can burn them up, as the internal cooling fan of the motor does not move enough cooling air. Some VFDs have thermistor inputs, or temp switch inputs for this protection if needed. I've never run into that issue, as I don't do continuous production as I'm just a make a part for some project I'm working on as a "fix broken stuff" guy.

 

[ajoeiam]

Any issues of EMI (or electro magnetic compatibility; EMC) are from long runs of wire between the VFD and motor, keep them less then 6ft/2meters long and you'll have zero issues of upset of any control wires used to remote the start stop speed. The manual has the requirements for the potentiometer (variable resistor) for remote speed control (Kohms and power rating). Just follow the manuals suggestions for the remote wiring.
Also NEVER put a switch between the VFD and motor, hard wire that. The reason is if you switch the motor while the VFD is running the motor, huge transient voltages can be created that blow up the transistors in the VFD, and at that point it's toast.
Also VFDs really are intended to be connected to one motor. They protect the motor from overload as that's a programable parameter in them, i.e. the motor HP and running current typically. So you can buy a much larger VFD, and program the motor size so it won't be overloaded. Running motors at very slow RPMs for long periods, can burn them up, as the internal cooling fan of the motor does not move enough cooling air. Some VFDs have thermistor inputs, or temp switch inputs for this protection if needed. I've never run into that issue, as I don't do continuous production as I'm just a make a part for some project I'm working on as a "fix broken stuff" guy.

More useful information - - - thanks!

 

[KellisRJ]

FWIW. I ran a BP M-head as others mentioned on the ~ middle pulley set, no problems. As screening criteria I suggest you consider this:

1. The manual is available to be read before purchasing. The really cheap units often don't and my experience is unhappy surprises.
2. Can you figure out how to make it do what you want?

I purchased a quality unit, and it was still a challenge to work from the schematic to get the correct external larger buttons and speed potentiometer wired up. The later one I was stuck with the buttons on the unit that were "OK" but I was spoiled by what I had previously.

What needs to be Normally Open, what needs to be Normally Closed. Once I did figure out how to use the information provided it got easier. One critical "note" was 3 pages after the schematic. Almost every sentence had some critical item to take note of, couldn't skim paragraphs looking for the quick answer. It was no where near plug n play.

The settings are often go to, example, 3, for breaking, then 32 to set the time and again 3 for i.e. 3 seconds. You can't just punch in 3323 and hit enter. If newer units let you do that, great!

So if there's no manual to see how good the Chinglish is, or you can't understand what you need to set, I'd look for another unit as the cost of frustration will be high.
Good|Quick|Cheap. You can have any two at the expense of the third.

 

[ddmckee54]

Ignator:

Regarding the obsolete AB/Rockwell drives. I've been working with AB drives since the 90's. I've got the PDF's for most of their drives, including the old stuff. Let me know if you can't find a manual, and I'll see if I've got a copy of it.

Don

 

[ignator]

I just purchased from eBay a Mitsubishi Electric FR-D720-042-W1 VFD for $69USD (brand new). This is a 1 HP max drive. I just tested it today with single phase power on a 1 HP 3 phase motor. This price is unbeatable. I could not find what the W1 means in the part number. That location is typically NA for North America delivered product. I was seeing these drives selling for crazy money. It's a very compact drive. So far I've only used the front panel to run the motor. But it has all the programmable inputs of any of the other brands and models I've used in my shop. There are several sellers of this same part number available. Appears these drives are surplus, as many sellers have them, but this was the lowest price I've seen. Just search for "FR-D720-042-W1" and you should see all the sellers of these.
These models are for three phase input, but this brand does not monitor for input phase lost and trip the inverter off on a fault code.
The only down side, the manual comes on a CD disk, but I found a pdf version for download (as none of my computers have a CD disk drive in them).

 

[ddmckee54]

I always thought that unless the drive was specifically designed for it, you needed to de-rate the drive when powering a 3 phase drive from a single phase source. (That old divide by the square root of 3 thing.)

But most likely that would be for a 100%, 24/7 duty cycle. It's probably stressing the drive running it like that, and the drive will have a shorter life. You might only get 25,000 hours out of the drive instead of the projected 50,000 hours.

 

[ignator]

I always thought that unless the drive was specifically designed for it, you needed to de-rate the drive when powering a 3 phase drive from a single phase source. (That old divide by the square root of 3 thing.)

But most likely that would be for a 100%, 24/7 duty cycle. It's probably stressing the drive running it like that, and the drive will have a shorter life. You might only get 25,000 hours out of the drive instead of the projected 50,000 hours.

The input diodes, are designed for single phase input up to the 3HP drive size. This I've gotten from many different forums with VFD experts commenting.
For larger then 3HP, the derating is double the Drive size for the motor. But that would be for full rated motor power delivered.
In my case I have a 10HP drive on a 7.5HP motor. I've only faulted the drive on undervoltage from too short an acceleration setting. I did add a huge power resistor for braking last year, as it would not decelerate, other then DC injection without that. Even with big depth of cuts and fast feed rates, I've never used the 7.5HP capability of the motor. I should put an ampmeter on the input to see what power is being used, just to have an idea of how hard I'm pushing my lathe. But I'm not production, and don't need to damage tooling.
What I don't know is which VFD brands monitor for input phase loss, and require the 3PH input to have all three phases connected. I've not run into that problem with TECO, Mitsubishi, Hitachi, or Weg that I have in my shop, and were all sold for 3phase input.

 

[timo_gross]

The big thing, first find the manual online, if you can't, don't buy the VFD.

That is my key decision maker recently for this kind of products. The name brand documentation and support is often (not always) just better. When much less time is spent to get it running, the higher price is quickly justified.

 

[user 284]

What pulley position to choose?

That's literally impossible to properly give any accurate answer for since it depends on just what your doing. I look at the material I need to machine, and with a mill, then the maximum and minimum cutting tool diameters I'm going to be using as the first two priorities. Then pick a belt / pulley position where I'm still going to be in the general ballpark of what I'd be using without the VFD and using a single ph machine. Even then, small or large diameter drills, end mills, face mills, fly cutters, power tapping, larger bored holes will still dictate when your going to have to shift that belt or use back gear. And fwiw, Bridgeport are cautious about listing in the documentation I've found on line about limiting the maximum spindle rpm to about 500 when you are using that back gear. With a new to you mill and looking for a VFD to power it, some forget that back gear also requires the motor to be run in reverse to then have the correct spindle rotation. It's less common today, but not all VFD's and especially the cheaper one's have that reverse option built in. So it's at least something to check before buying.

With an Asian sourced BP clone and what many don't seem to know. Then almost for sure it was also built to an Asian motor standard that doesn't conform to any of the more usual standards for Imperial or Metric frame off the shelf motors. That was pointed out by my industrial electrical supplier when I was buying my VFD. He also mentioned that "some" non VFD rated motors and it's apparently fairly rare, will refuse to play nice when powered with a VFD and can sometimes burn themselves out. My best guess is that probably happens when corners were cut on the amount and type of motor insullation that the motor manufacturer did. So just in case, I choose to vary my VFD by at most 30 Hz on either side of the motors rated rpm and change the belt position whenever I'd need to go outside that. It litterly takes less than 1 minute to change to a different pulley ratio, so I don't understand why anyone wouldn't do so. I'm using what was a quite expensive industrial rated 5 hp Baldor VFD on my mill, and even with it, the VFD would sometimes fault out in the top two belt speeds simply because the torque was a bit too high to get the spindle up to full rpm in the ramp up time the VFD was factory set for. Changing the parameters and adding 2 seconds to that ramp up time permanently fixed the only minor issue I've ever had with it.

I also have my VFD's hard wired into a seperate sub panel in my shop and an emmergency stop wired between that sub panel and each VFD . Unless I'm actualy using a machine, or when changing tools, those E stops are used to turn the supply power off to each one. And I'll trip the breakers for the whole shop anytime I going to be away from it for any length of time. In my opinion, buying any non UL compliant VFD just because it's dirt cheap is taking a massive chance if it ever did start a fire. You can virtually guarantee your home insurance would be worthless if any fire was ever traced back to it.