Needing VFD Suggestions - 1Ph to 3Ph

sparkie

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So we just wired up a small automotive shop. They bought a second-hand lift but only have a single phase service.

The motor is 3 phase, and the wiring on the controls is in pretty bad shape, so much of it will need replaced.

The controls are pretty simple. There is a momentary 3 position switch with a spring return for either up, down or off. There is an upper travel limit and lower travel limit for the motor. All of this can be controlled via a VFD pretty easily, and I think with the cost of salvaging the old controls and time involved, we can get a new system put in pretty quickly and it would be cheaper.

Here are the specs on the VFD I would need:

220V input single phase
3 phase 230V output
motor is 1135RPM and 4.9 HP
Need to have a couple inputs for the limit switches to stop travel.

I will use a contactor for power on/off to the drive

Can anyone suggest VFD's that will fit this profile?


The other option we have is to use transformers to create 3-phase, but I think given everything using a VFD is the way to go.
 
Hopefully more experienced VFD guys will be along presently, but in general you have to de-rate a drive by about half when you're supplying it with single-phase power, and 10 HP is getting close to the top end of the single-phase drive market.

Is the lift purely mechanical, or is it hydraulic ? Does it have sufficient mechanical braking to make lifting it safe if the VFD and motor stall ?
 
The lift is mechanical. Overall, the lift is pretty simple. It is a belt drive rather than a chain. As far as breaking, I'm still looking more into the lift and have no made any decisions yet. We do have a 200A service, and this is the only lift. Other than an air compressor and two gas pumps there isn't much potential load in the shop.

I have also been concerned about efficiency when converting 3-phase to single phase, so my first idea was to go with a motor, but it is a strange FC frame and an 1135 RPM motor, so I'm having a hard time finding a motor to fit the specs.

They bought the lift second hand under the assumption that "it can be wired for single phase" because it says so in the user manual, but you can't wire a 3-phase motor for single phase as far as I know.

I was just looking for two primary factors at the moment, safety and cost, in that order.

In order to prevent the lift from dropping, the safety mechanism has to be mechanical, as the controls are very simple. Maintain power button/lockable disconnect switch feeding the control circuitry, a motor starter, transformer to 24AC for the control circuit, the up and down switch I mentioned earlier and the two limits.

As far as derating, I'm having a hard time finding a drive above 3 horses that will do that job. We may end up having to repair the controls and using a single phase to 3 phase transformer.

The one good thing about the deal is that there is no wiring in place and the lift is right beside the panel, which means we can size everything properly from the get-go.

We may end up pricing a service change to 3-phase as well, but would hate to do that for one piece of equipment.
 
I'm afraid I have nothing useful to add, but I have to ask, is a 200A single phase supply common across the pond? That just seems like an extremely poorly thought through idea in general. I don't think I've ever seen a single phase supply over 100A here in Oz.
 
I have also been concerned about efficiency when converting 3-phase to single phase, so my first idea was to go with a motor, but it is a strange FC frame and an 1135 RPM motor, so I'm having a hard time finding a motor to fit the specs.

Sounds like a 6 pole (hence 1200 RPM) motor. You will have a hard time finding a replacement for it


They bought the lift second hand under the assumption that "it can be wired for single phase" because it says so in the user manual, but you can't wire a 3-phase motor for single phase as far as I know.

Nope. You can't (and have it drive a load).

As far as derating, I'm having a hard time finding a drive above 3 horses that will do that job. We may end up having to repair the controls and using a single phase to 3 phase transformer.

There are rotary three phase converters available, I bought a 20hp one for a friend, it was only $900.
 
I'm afraid I have nothing useful to add, but I have to ask, is a 200A single phase supply common across the pond? That just seems like an extremely poorly thought through idea in general. I don't think I've ever seen a single phase supply over 100A here in Oz.

Pretty common. When a builder decides to build a small strip mall, they have no idea as to what it will eventually be used for. So back in the day (70's - 80's), we put 200 single phase services in just about all of them.
 
rootboy, you would use a true "Roto-Phase" rotary phase converter that literally spins an armature for this purpose, rather than a "static phase converter" that will let you run a wye-wound motor at only 2/3 rating, right ?

Fortunately even a rotary phase converter wouldn't have a high duty cycle, even in an auto shop.
 
We have done several 200A single phase services. Larger dwellings often have potential to draw more than 100A when you figure in small workshops and such. Most of the commercial stuff in my town is single phase as well, so they will have 200A services put in to carry the load.

There is a TON of outdated electrical in my area, so we spend a lot of time upgrading too. I see knob and tube on a regular basis, as well as the old crimp and friction tape splices of the 40's and 50's. Actually, just replaced a lot of wiring in an old house like that today.

What about with transformers? My boss was suggesting that today as well.
 
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And they are easy to make, find a 3-phase (the idler) motor that is equal to or greater than the largest load motor (your lift). I prefer going 2x in idler HP, and that will be absolutely necessary if you are driving a heavy load such as hydraulics.

Wire the idler up across the single phase and then wire up the 3-phase service from the three leads on the idler. With the power off, and the lift disconnected from the idler, use a lawnmower pull rope to get the idler spinning. Turn on the power from the service, and the idler will speed up to nominal speed, once that happens, you can turn on the lift.

There are also ways of using a capacitor to start the idler motor in case you aren't crazy about the lawnmower pull rope method. :)

https://www.youtube.com/watch?v=Vm7sgy1JR1s

I built one back in the 80's so we could try out our drilling machine for elevator shafts. The drilling machine was 40hp, and we managed to get the thing running off of a 50hp idler powered by a 100 amp breaker. After the third time we reset the mains, that is... :)
 
We have done several 200A single phase services. Larger dwellings often have potential to draw more than 100A when you figure in small workshops and such. Most of the commercial stuff in my town is single phase as well, so they will have 200A services put in to carry the load.
Oh, there's plenty of large dwellings like that here too, but as soon as someone has a requirement for more than about 80A the supply authority just runs a three phase supply anyway. Domestic, commercial, whatever. The little differences like that between countries never cease to amaze me!

There is a TON of outdated electrical in my area, so we spend a lot of time upgrading too. I see knob and tube on a regular basis, as well as the old crimp and friction tape splices of the 40's and 50's. Actually, just replaced a lot of wiring in an old house like that today.
What on earth is "knob and tube"? I only ask because I really don't feel comfortable googling it :oops:

Sorry for the tangent!
 
rootboy, you would use a true "Roto-Phase" rotary phase converter that literally spins an armature for this purpose, rather than a "static phase converter" that will let you run a wye-wound motor at only 2/3 rating, right ?

Fortunately even a rotary phase converter wouldn't have a high duty cycle, even in an auto shop.

Yup, if you have to do this for anything above 5hp, rotary is the only way to go. The idler motor should be located near the machine, and the shaft of the idler needs to be guarded.

For heavy loads, size the idler 2x, or even 3x the hp of your machine's largest motor for the idler.

The rule of thumb is that you can drive up to four motors off of the idler (rotary converter). For example, if you had a machine with a 7.5hp, and three 5hp motors, size the converter for the largest motor, and it will "pick up" the other three as well. As an added benefit, as you add motors your power factor improves.
 
Well, we also use solid core copper wire and do our splices with wire nuts or stab-lok connectors for most residential and commercial stuff. When I worked at a packing plant it was mostly stranded THHN we ran because it was easier to pull. They both have their benefits. Our devices and switches also usually mount inside the wall, and we still use screws.

Knob and tube is an old wiring specification from the early 1900's where you would run the wires across porcelain knobs that were nailed into place. Also, rather than run a Line and Neutral for each device, they were also permitted to run the Line and Neutral wires separately from each other, which can be a real mess. Another thing that was allowed as fusing and switching of the neutral wire to break the circuit.

Just check it out on wikipedia, it is pretty cool but a pain to figure out what is going on at times when there have been additions to the wiring.

Also rootboy:

Yea, I'm not going to mess with building one. He can pay to buy one or not use his lift. It will be a bit of a pain reworking the controls, but I can live with that. I was hoping that I could just use a VFD and the VFD IO to handle the same task and eliminate the need for two sets of controls. Looks like that isn't going to happen now.
 
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We have done several 200A single phase services. Larger dwellings often have potential to draw more than 100A when you figure in small workshops and such. Most of the commercial stuff in my town is single phase as well, so they will have 200A services put in to carry the load.

There is a TON of outdated electrical in my area, so we spend a lot of time upgrading too. I see knob and tube on a regular basis, as well as the old crimp and friction tape splices of the 40's and 50's. Actually, just replaced a lot of wiring in an old house like that today.

Been there, done that. I was an electrician in Colorado many moons ago.


What about with transformers? My boss was suggesting that today as well.[/QUOTE]

Nope, won't work. :)

You've got a PM...
 
Been there, done that. I was an electrician in Colorado many moons ago.


What about with transformers? My boss was suggesting that today as well.

Nope, won't work. :)

You've got a PM...[/QUOTE]

Hah, my boss got his master's in CO. I have seen a lot of the work those boys do and it has always been pretty nice. I know he is damn good at what he does.
 
Technically, ANY VFD can be used to run a 3 phase motor from a single phase service, as long as you do two things:

  1. Double the VFD current rating from the motor FLA so that you have enough capacitance to smooth out the extra DC bus ripple. Don't listen to those that say you can just go up one size because it's about the current increasing by the sq. rt. of 3 (1.732x), that's an incomplete story. 2x is the MINIMUM.
  2. If you ever need full load at full speed from the motor, de-rate the operating temperature by about 25% because the capacitors will run hot doing the extra work. So if the VFD is rated for 40C in an enclosure, you must maintain 30C (77F) ambient inside of the box. That's tricky, so the alternative is to use a 65% de-rate factor on the current, meaning you take the motor FLA/.65 to size the VFD, then you can use it at its rated operating temperature. Or you can lower the Current Limit setting in the VFD (if it has that feature, some cheaper ones don't) to run it at no more than 75% torque, which might result in you not being able to run at full speed with a full load.
Once you get above 3HP at 230V, not all VFDs will work as a phase converter because some of them have Phase Loss protection that cannot be disabled.You need to make sure to check that before purchasing. I happen to know that all A-B VFDs will work, no settings necessary because they just monitor the DC bus ripple to decide if you lost a phase. The PowerFlex 70s don't need the extra de-rate because they have a built-in DC bus choke that removes some of the bus ripple burden from the caps. So you could buy a 10HP 230V PF70 drive for this. Other brands may work too, I just happen to know this one because I use them a lot. The PF40s and PF520s don't have the DC bus choke at that size, so they need the extra de-rating, as do most Asian drives (because almost none of them have DC bus chokes).
 
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