Three Phase to Single Phase Conversion?

[FlipFlopKing]

I just got a screaming deal on a Dake V-24 Band Saw and I'm looking at getting it set up in my shop. It's got a 2.2hp motor and is wired to be operated with an input voltage of 230, 3 phase, 60 htz
(+/- 10%).

I do not have three phase power in my shop, so I am faced with the decision of how to handle my power supply problem. The way I see it, I have two options:

1.) Replace the motor with a 240v single phase unit.
Pros: I have a 240V outlet already wired up in the shop.
Cons: I have no idea what would go into changing out the motor, I have to believe that there's going to be a little more to it than just swapping the motors out. Also, the three phase motor is more efficient and will last a lot longer.

2.) Buy a rotary phase converter and wire it up with that,
Pros: Maintain the bennefits of the 3 phase motor. Don't have to monkey around with the machine at all.
Cons: The breaker box is outside and I'd have to hardwire the phase converter into it. I rent the space and I don't think that the property manager would be too keen on me messing with the electric(even if I hired a professional). As much as I'd like to just wire the phase converter to plug into the 240v outlet (as the breaker is the correct size), I can't do it because the run is over 30 feet and I'm sure it is wired with something smaller than 8 guage wire (I'm sure those of you who are smart on electricity will have a littany of other reasons why that would be unsafe as well).

Any thoughts or advice?

 

[Sancho]

Have you considered a vfd? (variable frequency drive)

 

[Kirbot]

Have you considered a vfd? (variable frequency drive)

x2
Thats what I would suggest

 

[FlipFlopKing]

Have you considered a vfd? (variable frequency drive)

I've got to be honest with you... I have no idea what that is. I'm going to do a web search right now, but anything you can tell me about it would be greatly appreciated.

Cheers,
Scott

 

[Sancho]

Im not the best person to explain it technically. I do know you feed it 220 and you can get a slew of 3phase power options out of it.

I like to think of it as a magic box that opens the world of 3 phase machines to homeowners. For what they do they are tiny.

 

[930dreamer]

Look here, they also have a ebay sight.

http://www.driveswarehouse.com/Drives/AC+Drives/Variable+Torque+VFD/X200-022NFU.html

 

[toms73novass]

I would definately go with a vfd. I have done both a rotary phase converter for the wood working tools in my basement and VFD's on the mill and lathe in my garage. I LOVE the VFD in particular the ability to vary the speed of the motor with out having to switch belts on my mill or late most of the time.

 

[fatfillup]

Had not heard of VFD. What you have to watch is start up amps. If a machine pulls 10 amps under full load, start up amps for a split second can be 30. Your shop current can supply that "overload" for a split second without repercussions, don't know about VFD.

Also, if you swap motor from 3 to 1 phase, you will probably have it run heavier wire to the motor cause single phase draws more amps then 3 phase. Not a big deal but must be done.

 

[mag409]

Where instant reversing is not an issue, a simple static phase converter would also work fine. You can get one from Enco for about $150 to handle your motor size. The static converter uses a start capacitor circuit to get the motor spinning and then kicks out running the motor on 220 single phase. The disadvantage is that the motor will only run at 2/3 of rated HP but for this application that will not be a problem. I have both a rotary and static converter in my shop and use both daily. The VFD's are nice for variable speed changes, but the dake should be adjusted via a pulley sheave system rather then through electronics so the static converter would also work for this application. Just my .02

 

[Alchymist]

Some VFDs give the option of slow startup to reduce initial draw. Other features include dynamic braking and variable speed. VFDs were designed for driving motors.

 

[Sancho]

I would assume LRA/inrush is figured into the type of vfd you buy, typically they are sized by motor HP. If I remember right, inrush is roughly 3x running current.

Regardless they work very very well.

 

[larry_g]

I would assume LRA/inrush is figured into the type of vfd you buy, typically they are sized by motor HP. If I remember right, inrush is roughly 3x running current.

Regardless they work very very well.

As said above inrush current is tempered by using the startup ramp programmed into the VFD (variable frequency drive)
lg
no neat sig line

 

[hofferwood]

As said above inrush current is tempered by using the startup ramp programmed into the VFD (variable frequency drive)
lg
no neat sig line

Bandsaw= VFD. Speed control is SWEET
Here's my oldie. But never used (was a spare, and the orig. never broke)

And for acceleration ramp and decel. ramp, the only programing skills you need is a screwdriver

Chuck

 

[larry_g]

AS you look at options for powering up this machine keep in mind that if it has a blade welder on it that the welder may complicate things. If it has a welder the the rule of putting no on/off switch between a VFD and its load may be a problem. Something to understand.

lg
no neat sig line

 

[rsanter]

go with a VFD as it will also allow you to adjust the speed of the bandsaw

bob

 

[FlipFlopKing]

Had not heard of VFD. ...Also, if you swap motor from 3 to 1 phase, you will probably have it run heavier wire to the motor cause single phase draws more amps then 3 phase. Not a big deal but must be done.

didn't know about the increased amperage draw of the single phase motor. This kind of plays into my concerns with the rotary phase converter... if the motor is going to require a heavier wire, teh entire circuit will require the same heavier wire, won't it? If the motor will require more current after the phase converter (regardless of the type), it'll require more from the panel to the converter... the converter isn't going to create current.

I'm not real smart on electricity... Am I completely off base here?

 

[FlipFlopKing]

...The static converter uses a start capacitor circuit to get the motor spinning and then kicks out running the motor on 220 single phase. The disadvantage is that the motor will only run at 2/3 of rated HP but for this application that will not be a problem.

[/QUOTE]I have both a rotary and static converter in my shop and use both daily. The VFD's are nice for variable speed changes, but the dake should be adjusted via a pulley sheave system rather then through electronics so the static converter would also work for this application. Just my .02[/QUOTE]

Yeah, I was aware of the reduces horsepower when using a static converter.

This saw does have a variable speed mwchanism. It's got a transmission with a high a nd low gear... there is an adjustment wheel that gives complete adjustment in each gear... 50-5000rpm.

 

[FlipFlopKing]

AS you look at options for powering up this machine keep in mind that if it has a blade welder on it that the welder may complicate things. If it has a welder the the rule of putting no on/off switch between a VFD and its load may be a problem. Something to understand.

lg
no neat sig line

Yeah, I was just reading about that on another site about different kinds of phase converters... This machine has got an entire fuse box of it's own, I'm thinking that's going to create lots of issues for the VFD option.

 

[larry_g]

Yeah, I was just reading about that on another site about different kinds of phase converters... This machine has got an entire fuse box of it's own, I'm thinking that's going to create lots of issues for the VFD option.

A vfd may not be out of the question here. You have to understand if the welder is three phase or just single phase driven by one or two of the 3 phase legs. You may be able to drive the motor with the vfd and use 240 single phase to run the welder. Have you found a schematic for the machine? If so link it here so the group may have a look and advise.

lg
no neat sig line

 

[FlipFlopKing]

A vfd may not be out of the question here. You have to understand if the welder is three phase or just single phase driven by one or two of the 3 phase legs. You may be able to drive the motor with the vfd and use 240 single phase to run the welder. Have you found a schematic for the machine? If so link it here so the group may have a look and advise.

lg
no neat sig line

Schematic... heck, here's the entire electrical manual!
http://www.dakecorp.com/manuals/Model E-V Series - Electrical.pdf

 

[DocsMachine]

If it were me, I'd install the VFD onto or even into the saw in an enclosure. Then run 220V single phase into that enclosure, with a branch off to also feed the welder. Easy as pie.

The only tricky part will be to wire the existing on-off switch to the VFD signal input, but even that's pretty simple.

I don't recommend static phase converters- they basically run the motor on two of the three phases, so the motor only has 2/3rds it's rated HP. The VFD typically has a "soft start" feature- bringing the motor up to speed over a couple seconds- so there's little worry about too high a starting draw popping a breaker.

Doc.

 

[930dreamer]

I asked the owner of a DoAll bandsaw if the welder was single or three phase and I believe the answer was single phase.

Looking at the diagram the welder is single phase.

 

[bolecailey]

Can you run a 3 phase TIG off a VFD?

 

[rsanter]

Can you run a 3 phase TIG off a VFD?

you might but I dont think so
a vfd is ideal for a motor but to power a transformer Im not really sure about

bob

 

[larry_g]

If it were me I would use a rotary phase converter. You have two motors and the welder on the mains and quite a bit of control circuitry. I would make sure that the controls and the welder do not run off the generated leg. As Doc said you could add a VFD after the RPC to have variable speed if you need it. I don't think that Doc took into consideration the 3 phase grinder motor. I think I also seen a coolant pump in there.

lg
no neat sig line

 

[FlipFlopKing]

Yeah, I think I'm pretty much set on the Rotary Phase Converter... just trying to figure out the rest of the issue.

I'm thinking that my best bet is to see if I can get an electrician to rewire the existing 240v socket with 8 guage wire... to handle the current issue (if I can get it done under the radar, it should be transparent to the property manager and owner).

Then I can wire up the phase converter to plug right into the wall and hard-wire the phase converter to the saw with a power switch in beteween.

Thanks for all the input... it's greatly appreciated.

 

[Steve from Socal]

I faced a similar issue with my DoAll band saw. My saw has a single phase grinder but a 1 HP 3 phase coolant pump. I used an old 5HP motor as a rotary; my saw has a 3HP main motor. I used 8 gauge wire because my welder is 8KVA, in looking at the wiring for your saw your welder is under 4 KVA at 3800VA. You could use 10 gauge wire with no issues.

Steve

 

[hedjhawg]

Also, if you swap motor from 3 to 1 phase, you will probably have it run heavier wire to the motor cause single phase draws more amps then 3 phase. Not a big deal but must be done.

Wire gauge is related to amperage, which is inversely proportionate to voltage. It has no relationship to phase.

If the current motor is 240VAC Three-phase, you can swap in a 240VAC single phase motor with no change in wiring. If the current motor is 480VAC, you will need to step up the wiring due to the increased amp draw at 240VAC (all else being equal).

On my Walker-Turner band saw, I swapped out the 3PH motor for 1PH. Easy, fast, machine is awesome. Going to 1PH made sense since the variable speed changes were due to the gearbox/pulley.

On my Walker-Turner drill press, I used a VFD on the 3PH motor. Since I HATE pulley changes, this made sense to me as I can control spindle speed through the VFD.

 

[theoldwizard1]

1.) Replace the motor with a 240v single phase unit.
Pros: I have a 240V outlet already wired up in the shop.
Cons: I have no idea what would go into changing out the motor, I have to believe that there's going to be a little more to it than just swapping the motors out.

Seeing as the saw is set up with a multi-speed drive, swap the motor and the switch. I'll bet it be pretty easy and probably cost about the same or less than a VFD.

Unless you are going to run it in a production shop, where you would have 3 phase, the saving for running it on 3 phase isn't that huge.

 

[hedjhawg]

Seeing as the saw is set up with a multi-speed drive, swap the motor and the switch. I'll bet it be pretty easy and probably cost about the same or less than a VFD.

Agreed... a used motor can be had on the cheap, or you might even be able to swap someone your 3PH for a 1PH

 

[fatfillup]

Wire gauge is related to amperage, which is inversely proportionate to voltage. It has no relationship to phase.

If the current motor is 240VAC Three-phase, you can swap in a 240VAC single phase motor with no change in wiring. If the current motor is 480VAC, you will need to step up the wiring due to the increased amp draw at 240VAC (all else being equal).

On my Walker-Turner band saw, I swapped out the 3PH motor for 1PH. Easy, fast, machine is awesome. Going to 1PH made sense since the variable speed changes were due to the gearbox/pulley.

On my Walker-Turner drill press, I used a VFD on the 3PH motor. Since I HATE pulley changes, this made sense to me as I can control spindle speed through the VFD.

Not so, and I speak from 28 years of experience selling and servicing electric powered equipment. Just a quick look in the Grainger catalog and a 5 HP 1 phase motor pulls 26 amps and 230 volts. The corresponding 3 phase motor pulls 13.9 amps. For the single phase motor, 10 gauge wire is needed and for the 3 phase motor 14 gauge would do.

 

[hedjhawg]

so... amperage determines gauge. We agree.

 

[fatfillup]

so... amperage determines gauge. We agree.

Yes we agree that amperage determines gauge, but I got the impression that you didn't know a given HP motor will draw more amperage at single phase then 3 phase. By just switching a given HP motor from 3 phase to single phase of the same HP, amperage will go up. And if a machine is designed for a certain HP, I assumed the same HP motor would be used as a replacement, thus the need to upgrade the wiring.

If I misinterpreted your post, I apologize.