Another VFD Question

[JR49]

On some of the You Tube vids about VFDs, they talk about getting a "2 HP rated VFD to use on a machine with a 1 HP 3 ph. motor", or a " 1 HP rated drive for a 1/2 or 3/4 HP motor. Are there any benefits to using a higher rated VFD than the 3 phase motor you will be using it on? Also, for you electrical guys out there, How about an outright Product recommendation. My lathe is a Logan 12 X 36 model #2557 VH, It uses a 1 HP 220V. 3 phase motor WHAT SAY YOU? thanks JR49

 

[DMS]

I am running a 1.5kw VFD (2HP) on my 1.5HP mill. Not sure why folks recommend going so much oversize other than the "bigger is better" idea. The VFD I have actually has 2 ratings, depending on how you configure it. IIRC constant voltage and constant current modes had separate ratings, and the constant current mode was lower. For units that don't have both ratings, the "oversized" recommendation may be to account for running in constant current mode on a unit with a faceplate value rated for constant voltage.

As far as products, I am using a Hitachi WJ200-015SF http://www.hitachiacdrive.com/hitachi-wj200-series-wj200-015sf/ and I have been quite pleased with it. It's not the cheapest out there, but it had the features I wanted and cost was not crazy.

 

[hvontres]

+1 on the Hitachi Wj-200 series. The thing to check when sizing a VFD is the Full Load Amps (FLA) on the nameplate for the motor. Then choose a VFD that is rated for at least that amount fo current. Ususaly that is the continous current rating. The Hitachi drives can supply up to 200% tourque on startup. One other thing to keep in mind is that VFD's can produce high voltage spikes that may damage the insulation on older motors. I added a three phase Reactor between the VFD and my mill to help reduce the spikes and protect the motor on my Bridgeport. Newer Motors tend to have new types of insulation that are designed to handle the spikes. If you decide to switch motors, look for an "Inverter Duty" one. Can you post a picture of the nameplate on the motor?

One other thing to keep in mind is that the power from the motor will reduce at low speeds. When using mechanical means (step pulley or Reeves drive) to change the speed, the motor is still running at the nominal speed and putting out 1HP. When you run the motor at 1/2 Speed, you are now only getting ~1/2 HP.

Ok, I just checked, and the 2557 has a variable speed drive. If it is still in good condition, I would reccomend using the VFD to generate 3 phase and using the original Variable speed setup to change speeds. This is what I have on my Brigeport J2 head and it works out really nice. One other thing I highly recomend is getting a braking resistor to help incrase the DC braking capabilities of the drive. On the bridgeport, I can stop the spindle in about 1.5 s, even at high speeed in backgear. And using a similar setup on my Clausing lathe, I can stop my 8" three jaw in about 5s. The Hitachi drives already have a dynamic braking unit built in, so adding the resistor is fairly simple. It's job is to make sure that the DC voltage inside the drive does not exceed the upper limit while braking, when the motor is actually acting like a generator. I am using a 500W 50 Ohm resistor that I got from e-bay for about $30.

Hope this helps.

PS: looks like you aren't too far away

 

[sparkness]

On some of the You Tube vids about VFDs, they talk about getting a "2 HP rated VFD to use on a machine with a 1 HP 3 ph. motor", or a " 1 HP rated drive for a 1/2 or 3/4 HP motor. Are there any benefits to using a higher rated VFD than the 3 phase motor you will be using it on? Also, for you electrical guys out there, How about an outright Product recommendation. My lathe is a Logan 12 X 36 model #2557 VH, It uses a 1 HP 220V. 3 phase motor WHAT SAY YOU? thanks JR49

You can absolutely use a 1hp VFD for a 1Hp motor that is what it is rated for, no need to go to a larger model, you can use a larger vfd on a smaller motor . I have used several different brands, and each have some good features. automation direct and teco are the least expensive and easy to program. the automation direct 1hp does not have the ability to use a brake resistor but has some built in braking. you can display scaled rpm , amps. Mitsubishi is a bit of a pain to program but offers a lot of features. As hvontres stated using a larger motor is good for when you use slow speed . on my 10" sheldon i have 1hp motor and vfd, I no longer use the back gear - just turn the knob on the vfd . I also run the motor up to 50% faster at times to get more rpm for finishing . Search the internet and you will find several places to get a good deal. I recommend buying new as apposed to used off of ebay because people selling used ones seem to ask way too much. here are a few sites which I have purchased from and had no problems. www.automationdirect.com www.dealerselectric.com www.factorymation.com

 

[itsme_Bernie]

I met Dealers Electric guys at Cabin Fever once, and purchased a Teco for up to 1HP. I love it.



Bernie

 

[Smudgemo]

I have a Teco on my small horizontal mill & the Hitachi wj200 on my vertical. Both are great, but the Hitachi seems nicer. More robust? I haven't seen any complaints for either.


Sent from my iPhone using Tapatalk

 

[jim18655]

3 phase VFD connected to 1 phase may need to be derated depending on the model and size of the motor. You'll need to read your book to see if it applies to your setup. Most likely scenario would be to multiply the motor FLA (full load amps) by the square root of 3 (1.73) and use that answer to find the size of the drive you need.

 

[hvontres]

3 phase VFD connected to 1 phase may need to be derated depending on the model and size of the motor. You'll need to read your book to see if it applies to your setup. Most likely scenario would be to multiply the motor FLA (full load amps) by the square root of 3 (1.73) and use that answer to find the size of the drive you need.

Or make sure that your VFD is set up for single phase input. The WJ-200's come as either SF (single phase) or LF models.

 

[countryguy]

Re: Some other considerations for VFD HP+1 formula : Another VFD Question

And you'll find that many motors are now "inverter rated" which accounts to the VFD type tech. If your motor is not, you may want to do some research on many of the VFD settings and what your motor can accomodate. The comment about the older motors and burning out is out there. Many documents have pics showing this burn out event in the windings. With VFD driven it's so east to run the Hz up and see boosts in RPM. When you do this, another reason to possibly consider going over on theVFD side is that you will run the HP motor beyond it's design. I did buy the 3HP for a 2HP Mill motor and 1HP lathe motor on my Shopmaster combo unit. LOVE that WJ200! Wowza! another thing I learned was the CT and VT ratios. 10:1/ 4:1 and the CT 1000:1 which I bought. as these motors are "paramatized" and delt HF blow's you can see how the "inverter rated" motors become almost a "must" consideration. (IMO). Also the IMax and RPM CT/VT roll off's when you push and pull the RPM's up & down may not do what you need. Just some comments while this is all fresh in my head from a week of VFD replacement on my Mill. What an adventure!
CGout.

 

[JR49]

Thanks everyone for the great responses. As a total newbe I learn something from every response. hvontres, about your PS, unfortunately I'm still not that close yet. Although, thanks to this forum, I think I've learned enough to be able to "Power up" the lathe. BUT the total hip replacement surgery I had last month will keep me from running the electric to the lathe for at least a few more months, not to mention even getting on the floor to read the specs off the motor plate, so I get the correct VFD. However, even on crutches, I spend a lot of time out there figuring things out and coming up with more questions for you guys. So thanks to all of you for keeping my recuperation, from getting boring, JR49