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VFD vs Phase Convertors

Weasel

Weasel

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Black Hills, SoDak
Ended up with a large 150 ton press with a 10' working die. It has a 15hp 3 phase motor that runs it. Have a estimate of about $2400 for a phase convertor from Phase Convertors North America.

I lean towards running a VFD but the recommended unit from Eaton would be a 30hp and run about $3400. But I'm not even sure it would work as the hydraulic pumps needs power right off the start, not like a fan or pump that can ramp up. I've seen some people recommend a vector drive VFD but guess at this point not sure how a VFD would be better then the PC at $1k more. Also planning on running a hoist, TIG, and maybe something like a water jet off it at some point.

Thoughts?
 
Get the phase converter. You will thank yourself when you get a second machine that needs it.

Edit: Meant to say phase converter.
 
Last edited:
How will a VFD help a second machine? I would get a rotary phase converter and wire it to a three phase panel for future equipment.
 
If you plan on running other things especially Cnc equipment I would lean towards a phase perfect converter. A vfd will be hard to run multiple pieces of equipment. If you have a bunch of dumb equipment a rotary is just fine. I have a rotary that runs my machine shop with no issues.
 
x3 on the Rotary. You can still run a VFD off the rotary if you need the variable speed or other features it may provide, but rotary will be cheaper in the long run for running multiple machines.
 
You can add a capacitor start circuit to spin the motor up and run 2/3rds hp. Overall cost is about $50. Only uses two properly sized capacitors and a momentary switch.

20200823_181205.jpg
 
Dethmachinefab said:
You can add a capacitor start circuit to spin the motor up and run 2/3rds hp. Overall cost is about $50. Only uses two properly sized capacitors and a momentary switch.
Click to expand...


How do you size the caps? I need to try this on my lathe. It's not playing well with the super cheap chinese VFD I have and I'd like to rule out the motor being fuct before I spend more on a real VFD.
 
That's an awesome press, damn. Rotary phase converter FTW.

Re: capacitor start. Seems like it behaves as a DIY static phase converter to me. Works fine as long as you don't (obviously) need full power of whatever you're running.
 
bgaidan said:
How do you size the caps? I need to try this on my lathe. It's not playing well with the super cheap chinese VFD I have and I'd like to rule out the motor being fuct before I spend more on a real VFD.
Click to expand...

I've got a 500uf on the hydraulic shear and an 500uf and 400uf in parallel the big mechanical press brake. Brake is 10hp, and shear is either 7.5hp or 10hp. I'm sure there is a method, but years of trial and error found these work well. Also start up loads play into the sizing.
 
GLTHFJ60 said:
That's an awesome press, damn. Rotary phase converter FTW.

Re: capacitor start. Seems like it behaves as a DIY static phase converter to me. Works fine as long as you don't (obviously) need full power of whatever you're running.
Click to expand...

Exactly, its the guts of a static converter that you operate manually on start up. It works well on a machine that runs constantly, and has inertia. Hydraulic machines less so, and you probably should add a motor to the circuit to make it a rpc. Overall you can build a rpc for darn cheap.

I always recommend a vfd when possible, but some machines are not practical to run one on single phase input.
 
Weasel said:
But I'm not even sure it would work as the hydraulic pumps needs power right off the start, not like a fan or pump that can ramp up.
Click to expand...

Hydraulic pump should need minimal power right from the start unless you're starting the motor with the ram under load and there's no control valve. I'd expect there to be very low backpressure on the pump during startup, so it should have low load. Power is proportional to pressure, and pressure in turn to load.

That being said, running a 15 hp motor off single phase is going to be lots of amps no matter how you do it.

If you have other stuff to run, a RFC would probably be the best overall setup, just be aware that it may be difficult to balance correctly with all those different size loads, so be careful with electronics heavy stuff.
 
sdmuleman said:
How do you get 2/3 hp? You're only powering one of the 3 phases, so I'd expect 1/3 hp.
Click to expand...

Like aczlan said above. L1 and L2 coming in, then power from L2 goes to a momentary switch then cap bank and out to L3.

To operate hold momentary switch, hit start button, motor spools, and release button.
 
aczlan said:
Looks to me like he is feeding L1 and L2 from the panel to those phases.
L2 is also feeding the cap bank which feeds L3.

Aaron Z
Click to expand...

Which means that the only effective coil is the one between L1 & L2 - L1-L3 & L2-L3 aren't energized, i.e. 1/3 of rated power. 2 wires /= 2 phases.
 
sdmuleman said:
Hydraulic pump should need minimal power right from the start unless you're starting the motor with the ram under load and there's no control valve. I'd expect there to be very low backpressure on the pump during startup, so it should have low load. Power is proportional to pressure, and pressure in turn to load.

That being said, running a 15 hp motor off single phase is going to be lots of amps no matter how you do it.

If you have other stuff to run, a RFC would probably be the best overall setup, just be aware that it may be difficult to balance correctly with all those different size loads, so be careful with electronics heavy stuff.
Click to expand...

That's just what I was told. Haven't dug into it enough to seem. I do seem to recall needing around possible 80amps at start up. So yeah it's a bit high. We will only be running 1 machine at a time on the RFC so will balancing still be an issue?
 
So slight sidetrack, but mostly related.

I have this cheap, $120 VFD. 3hp rate and runs off 120v input.

https://www.amazon.com/gp/product/B...h_asin_title?ie=UTF8&psc=1&tag=91812054244-20
51lSsgMmm4L._AC_SL1000_.jpg


I bought it mostly as an experiment because it was cheap. The hope is that I could run my 3hp Lagun mill off of it and then I picked up my Cincinnati lathe that's also 3hp. If it worked, it'd open up a lot of possibilities for people who don't even have 220 available.

So hooked up to either the mill or lathe, it'll turn the motor and I can play with the speed to get it where it's mostly stable and has decent torque. But there's a very narrow range in the speed knob that lets them run. If you crank it up too high or too low, it'll just cut out. I also found that with the lathe, when I'd drop the clutch in or out of neutral, it'd cut power. Sometimes it'd ramp back up and other times it wouldn't. If I started up with the clutch engaged, it'd be ok.

I played with a bunch of the parameters and was 98% sure I had them set right for the motor, but it would never work as it should with the variable speed knob.

I figured it was just the VFD was a POS and didn't work.

But then I hooked the lathe up to the ABB that runs my 3hp belt grinder and acted the exact same way - I could find a sweet spot in the speed, but it was touchy and would cut it if I went to high or low.


I also hooked the chinese VFD up to my new baldor pedestal grinder and it works perfectly - full range of speed down to almost nothing and I can crank it up to max with no issues.


So it makes me think I have a parameter set wrong for the specific motors on the mill and lathe. Pretty much the only things you usually set are voltage, speed and number of poles. All of which I was pretty confident I had right.


I'm kind of baffled at this point, but I'd love to figure it out.
 
bgaidan said:
So slight sidetrack, but mostly related.

I have this cheap, $120 VFD. 3hp rate and runs off 120v input.

https://www.amazon.com/gp/product/B...h_asin_title?ie=UTF8&psc=1&tag=91812054244-20


I bought it mostly as an experiment because it was cheap. The hope is that I could run my 3hp Lagun mill off of it and then I picked up my Cincinnati lathe that's also 3hp. If it worked, it'd open up a lot of possibilities for people who don't even have 220 available.

So hooked up to either the mill or lathe, it'll turn the motor and I can play with the speed to get it where it's mostly stable and has decent torque. But there's a very narrow range in the speed knob that lets them run. If you crank it up too high or too low, it'll just cut out. I also found that with the lathe, when I'd drop the clutch in or out of neutral, it'd cut power. Sometimes it'd ramp back up and other times it wouldn't. If I started up with the clutch engaged, it'd be ok.

I played with a bunch of the parameters and was 98% sure I had them set right for the motor, but it would never work as it should with the variable speed knob.

I figured it was just the VFD was a POS and didn't work.

But then I hooked the lathe up to the ABB that runs my 3hp belt grinder and acted the exact same way - I could find a sweet spot in the speed, but it was touchy and would cut it if I went to high or low.


I also hooked the chinese VFD up to my new baldor pedestal grinder and it works perfectly - full range of speed down to almost nothing and I can crank it up to max with no issues.


So it makes me think I have a parameter set wrong for the specific motors on the mill and lathe. Pretty much the only things you usually set are voltage, speed and number of poles. All of which I was pretty confident I had right.


I'm kind of baffled at this point, but I'd love to figure it out.
Click to expand...

Does it display a fault? I know The abb should. The narrow operating window problem seems odd to me. That thing should creep on a few Hz and run fine anywhere up to max Hz. Try putting everything back to default values.
 
Dethmachinefab said:
Does it display a fault? I know The abb should. The narrow operating window problem seems odd to me. That thing should creep on a few Hz and run fine anywhere up to max Hz. Try putting everything back to default values.
Click to expand...

No errors at all. All I need to do is fiddlefuck with the frequency knob and I can get them to ramp back up. I've reset it a couple times and followed some tips on setting the parameters that someone posted on youtube. I was ready to write it off as just being a POS until it worked perfectly on the grinder. The only difference is that the grinder is 1.5hp and the other two are 3.....but they were acting up without any load on them at all. And then when I tried the ABB VFD and it acted the same way, it makes me think it's something about the motors themselves that are causing the weirdness.
 
American Rotary is having a 25% off sale today, in case any of you are on the cusp of buying a VFD or Rotary setup.

CYBER25 is the code.
 
The vfd gets de-rated for single phase input to 3 phase output. I would not be surprised the 3hp is for a 240 volt 3 phase input.
 
cj3a said:
The vfd gets de-rated for single phase input to 3 phase output. I would not be surprised the 3hp is for a 240 volt 3 phase input.
Click to expand...

Generally a VFD that is designed for single phase input is labeled for the actual motor output....but with a cheap chino one, who knows? I know the automation direct ones labeled for the actual motor size.


But even then, you'd think it'd only have an issue when there was a big enough load on the motor to draw more than the (de)rated amps.
 
bgaidan said:
So slight sidetrack, but mostly related.

I have this cheap, $120 VFD. 3hp rate and runs off 120v input.

https://www.amazon.com/gp/product/B...h_asin_title?ie=UTF8&psc=1&tag=91812054244-20


I bought it mostly as an experiment because it was cheap. The hope is that I could run my 3hp Lagun mill off of it and then I picked up my Cincinnati lathe that's also 3hp. If it worked, it'd open up a lot of possibilities for people who don't even have 220 available.

So hooked up to either the mill or lathe, it'll turn the motor and I can play with the speed to get it where it's mostly stable and has decent torque. But there's a very narrow range in the speed knob that lets them run. If you crank it up too high or too low, it'll just cut out. I also found that with the lathe, when I'd drop the clutch in or out of neutral, it'd cut power. Sometimes it'd ramp back up and other times it wouldn't. If I started up with the clutch engaged, it'd be ok.

I played with a bunch of the parameters and was 98% sure I had them set right for the motor, but it would never work as it should with the variable speed knob.

I figured it was just the VFD was a POS and didn't work.

But then I hooked the lathe up to the ABB that runs my 3hp belt grinder and acted the exact same way - I could find a sweet spot in the speed, but it was touchy and would cut it if I went to high or low.


I also hooked the chinese VFD up to my new baldor pedestal grinder and it works perfectly - full range of speed down to almost nothing and I can crank it up to max with no issues.


So it makes me think I have a parameter set wrong for the specific motors on the mill and lathe. Pretty much the only things you usually set are voltage, speed and number of poles. All of which I was pretty confident I had right.


I'm kind of baffled at this point, but I'd love to figure it out.
Click to expand...

Right in the specs:
  • Input：1 or 3 phase 110V. Output：3phase 110v. Frequency：0-50hz/60hz. 0-400hz.
So your running the motor at half voltage, its going to be a grumpy turd.

They do have step up units, but I've only seen them up to 1.5 hp. Now, on a decent lathe you can do a lot with just a 1hp motor, my SB does just fine. You could also try running a 3hp motor, it would probably start just fine, but if you overload it the brain box may give out first.


I just bought this one https://www.amazon.com/gp/product/B01DKJWM62 for my surface grinder. It was half the cost of the automation direct one, kind of a gamble but if it sucks amazon has a good return policy. Asked with the amazon question BS if you could drive a DC relay off the control pins and got 3 yes and 1 no. Didn't realize it was a poll, or maybe its odds of it working
 
Whitbread said:
Build your own rpc. Buy a used motor from Craigslist or marketplace and a panel from WNY Supply. I have $450 in my 20hp setup with a Baldor idler. No reason at all to pay $2k+.

http://phaseconverterusa.com/Standard-Series_c_27.html
Click to expand...

There's no reason to be buying a panel either. The wiring diagrams and discussion of how to size the components are all over the internet. There's like $50-$100 of components in those boxes. Not worth it IMO. Also odds are whatever box you're using for your fuse and switch had plenty of free space inside for the caps so you may as well install them there.
 
kf4zht said:
Right in the specs:
  • Input?1 or 3 phase 110V. Output?3phase 110v. Frequency?0-50hz/60hz. 0-400hz.
So your running the motor at half voltage, its going to be a grumpy turd.

They do have step up units, but I've only seen them up to 1.5 hp. Now, on a decent lathe you can do a lot with just a 1hp motor, my SB does just fine. You could also try running a 3hp motor, it would probably start just fine, but if you overload it the brain box may give out first.


I just bought this one https://www.amazon.com/gp/product/B01DKJWM62?tag=91812054244-20 for my surface grinder. It was half the cost of the automation direct one, kind of a gamble but if it sucks amazon has a good return policy. Asked with the amazon question BS if you could drive a DC relay off the control pins and got 3 yes and 1 no. Didn't realize it was a poll, or maybe its odds of it working
Click to expand...

Good catch. I never noticed the lower output voltage rating. I need to probe it next time I run it to verify.

Still doesn't make sense why 2 out of 3 apparently identical motors (at least in the sense of poles, HP, RPM, etc.) will not run normally on it but the 3rd one seems fine. And I also tried a known good 220v vfd on the same lathe motor and it acted up too.
 
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