phase converter question?

C

chuck furniss

Guest
rotary vs. static.
one is cheep the other is pricey.what is the difference? pro's and cons?.
I will be doing barrel work again after a 30+ year hiatius and am in the market for a good used lathe.currently looking at a logan but I think the deal is going to fall trough.
thanks for opinions.

Chuck Furniss
 
I think that a static converter for a small hp motor for a good lathe is OK. If you are like the rest of us, buy a big rotary and run everything off of that. I just don't get the guys that want to keep beating a dead horse with a big single phase, the world is full of lots of three phase motors that go begging second hand.


I broke down and bought a use 15 hp rotary phase converter years ago and don't have to worry about losing out on good deals for use motors anymore.


It is sure nice not to have to shut down one motor to run another. Let the programme run when you jump on the Lathe is nice way to go. Or not worrying about the compressor coming on while you are in to another project.
 
I agree with Al, a BIG rotary phase converter works extremely well. There is no issue with running several machines at the same time off it and heavy starting loads like an air compressor while another machine or two are running does not affect any other 3 phase equipment that is running at the same time.

However, for all that, if its a small lathe or milling machine and will be your only 3 phase piece of equipment, I hear plenty good things about the VFD digital electronics speed control single phase to 3 phase converter systems. If I had a need, I think that's what I'd try...

Happy shooting,
Mitch & Shadow...
 
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A 3hp converter will run a couple machines or more that are 3hp or less at the same time. Just start them separately. I have 2 VFDs that power my 2 step pulley Bridgeports. They are very nice and give me variable speed and instant braking.
Butch
 
I agree with Butch - if you're looking at running one or perhaps two 3-phase motors, the VFD is a great option. I've got a couple of them running my two 3hp lathes, and couldn't be more satisfied. The really nice things about VFDs are the ability to program them for a 'soft' start - particularly on a lathe - and the variable speed feature.

I've heard some comments in the past about rotary phase converters being 'noisy', and they do make enough noise to be noticable when running, but then, so does a VFD's cooling fan. If you're looking at setting up a large shop and filling it with several machines, a rotary converter makes sense. However, one thing to consider is that it takes electricity to run one. We've got a 10hp rotary running one of our irrigation sprinklers, and another identical sprinkler running off a 3-phase line. The monthly bill for the machine running on the converter is roughly double what it costs to run the other one.
 
If your bill is double running a phase coverter you have got something wrong, unless of course you are running the converter 24-7 and only running the pump part time or a 10hp converter and a 1hp pump.

Well that would be something wrong as well.
 
VFD is the way to go..

Butch and others have given you some good advice..

There are several web sites dedicated to just selling VFDs. "Dealersdirect" comes to mind.

You can figure on spending about $100.00 per horse power rating for a new VFD and less for a used one.

If you are running one piece of equipment the cost is minimal. If you are runing and entire shop it can be more expensive.

Nat
 
Another vote for VFD.
More control of your machine's operation.
Not very expensive.

I got mine from www.factorymation.com

They have great support and will help you choose the right model for your needs.
 
I use VFD's daily but for a totally different reason, as we have unlimited access to 480-3ph usually.

VFD's are an economical alternative for small motors.

I like rotary's for larger motors and at one time ran CNC's on a homemade rotary.

All you need is a 10-20 hp 3 phase motor, min 1750 rpm, 3450 preferred and a 3ph knife switch. once it's started it's works really well.

Thats really all a rotary is, actually, all in a neat pricey package.

The down side is a rotary runs continuously and uses power even if the tool is down, you usually let them run all day, or you have to start and stop them all the time.
 
Phase converter question?

glbreil said:
If your bill is double running a phase coverter you have got something wrong, unless of course you are running the converter 24-7 and only running the pump part time or a 10hp converter and a 1hp pump.

Well that would be something wrong as well.
Click to expand...

I suspect that the reason for the cost difference may have to do with the way the power company bills 3 phase power versus single phase.

Scott Roeder
 
The irrigation sprinkler I spoke of is a quarter-mile long center pivot machine, with seven towers, each with its own motor. And yes - it runs 24-7, all summer long - flat tires, seized gearboxes, or a burnt-out rotary converter notwithstanding. It typically takes 5 days to make a complete revolution, putting on approx. 1.5" of water in the process. The individual tower motors run in sequence, keeping the sprinkler straight within its safety limits. I doubt there's anything wrong with it or the way it's wired - everyone I've spoken with who has a sprinkler on a phase converter tells me it's much more costly than running directly on a 3-phase line.
 
flatlander

Your converted power is not 100% your 3ph would be. That 10hp rotary is not 100% efficent and is also another load added to the single phase which is possibly at 60-70% and is therefore creating a larger load thus costing more money.

Depending on your service for the single ph and the 3ph there could be a different rate......Where I live 3ph gets you commercial rate, they would not give me 3ph for a residential garage.

I'd be changing those motors yesterday and getting that unit on 3 ph if it were me. That's unless the want to charge $125,000.00 per mile to get you 3ph service.

All converters are a compromize and add to the power cost.

The VFD's are really working well to control motors once you get the hang of programing them. The accel and decel , braking all neat features you will not get with a rotary.
 
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