3 Phase to Single Phase

[DieselAddict]

Do you have commercial refrigeration? Most home refrig's run on 120v. If your running a 120v machine on 208 (coming from 2 legs and not one leg to neutral), then it's getting too much voltage.

Sorry, I was teasing you since residential units are 120v.

 

[jaws4518]

Sorry, my bad! I mean rated for 220/208. I was thinking either/or. Configurable or switch-able would apply to a welder or power supply. I do have two industrial motors that handle either voltage. I will have to look again, but I believe there is a wiring diagram on the data plate. I don't know if there is some special about these that they do a 3 wire connection. I'm not an expert in all the how-to or possibilities. Another example would be my compressor. It's not rated for 208. In my situation around here my compressor and AC unit condensers are the voltages I have to worry about.

 

[DieselAddict]

3 phase induction motors are much different from single phase induction motors. There isn't any practical way to make a motor that could be easily switched between them.

With the rise of VFDs you can easily run a 3 phase motor on single phase since the VFD takes the single phase, turns it into DC, then back into 3 phase AC.

 

[Triple Jim]

Just read all the specs before you buy a VFD, because many have 3-phase in put as well as output. In my experience, they're really the way to go, if you have 3-phase equipment that you need to run on single phase. Not only will that problem be solved, but you'll have the ability for variable speed, soft start, overload protection, and many other features.

 

[tobyS]

Sorry, my bad! I mean rated for 220/208. I was thinking either/or. Configurable or switch-able would apply to a welder or power supply. I do have two industrial motors that handle either voltage. I will have to look again, but I believe there is a wiring diagram on the data plate. I don't know if there is some special about these that they do a 3 wire connection. I'm not an expert in all the how-to or possibilities. Another example would be my compressor. It's not rated for 208. In my situation around here my compressor and AC unit condensers are the voltages I have to worry about.

The problem is that today, most things are built to the edge of their rated duty cycle and no more. Some call it a throw away society. The amount of copper is the issue. Motors rated for 208 have slightly more copper in the windings because they draw more amps. Heating makes resistance go up and more heat...to possible, but not certain failure.

Spend a few bucks for a 3 phase transformer to bump it up, even if you only use one or two legs.

A note about freq drives for using 240V single to make 3 phase. If you have a used unit, turn it on and let it sit for a day or two, without running the motor. They will fail quick if they don't have the electronics warmed up prior to putting a motor load. Great on drill press and lathe.

 

[Dwnorton1]

Typically 3 phase motors are usually tapped (9 lead ) where you can configure them for 3phase 208v or 3phase 480v. Single phase motors are typically 240v with sometimes being able to be wired 120v with twice amp draw. Never seen one that could be wired as either 1 or 3 phase.

That being said that is where gain in efficiency is with 3 phase motors over single phase motors by utilize full cycle of generator firing each phase 120degrees from prior.

 

[jaws4518]

I do have military split-pack HVAC unit. The condenser has a mounting flange that is made for tractor trailer mounting. Looks like a refrigeration unit. The air handler is a rack mount unit. It will do 208/220.

 

[tobyS]

A motor winding for 230 and 460 but without a rating for 208 will (likely) be 10% less copper (draws 10.7% more amps based on voltage, single phase). Older motors tended to be more generous, but don't count on it. Why take the chance when you could bump it up. There appears to be some confusion...he has a 3p generator that makes 208 and 2 motors that are 240v 1p.

My suggestion is to buy a 3 phase transformer 240-208 and in-feed the 208, then take up to 3 (A, B, C) single phase 240 loads. Putting both on one pole is not the way to go due to exceeding VA on one pole.

 

[jaws4518]

I believe what you are describing is what I'm talking about. I believe the 3 phase transformer is what I priced at around $2500. It's a big transformer if you want 30 amps at 240 out. It's been over a year since I researched what I might need. In the beginning, I thought I was going to scrounge up some single phase transformer and boost the voltage up to 220 on one leg, then I started diving into all the how-to articles to achieve this. You can find this on YouTube, and it seems like there are several methods based on the application. I could be talking out my rear, but I believe the diagram I am referring to show a delta being created between the one of the three phases. I believe it is proper and balanced with respect to neutral. Again, if I sound like I do not know what I'm talking about, then I apologize. I will revisit my study on this when I am ready to create the solution I'm looking for. Then, maybe there is no real need other than learning to transform 208v to 220v running the generator in three phase mode.

 

[tobyS]

I sold the 3p I was using to the jail for $500 and they leave it permanently attached (they wondered why their welders never worked quite right). They are out there cheaper than $2500, but that is probably a retail price for a larger one.

 

[jaws4518]

Right. Maybe this topic is kinda like adding a turbo to the NHC 250. You can experiment and do it, but the cost vs. benefit is not that great. So, concerning my situation and my MEP-003a, probably best to use the 120/240 single phase method unless something or some power configuration need warranted a 3 phase scenario.

That sound about right?

 

[jaws4518]

Thanks Triple Jim. Doing a good referb of my MEP 003 is in the project pipeline. I had to make new injector lines for it after I bought. A couple of them were slightly touching the engines cooling fins and rubbed hole in them. I will keep you regulator in mind.

 

[dav5]

Just read all the specs before you buy a VFD, because many have 3-phase in put as well as output. In my experience, they're really the way to go, if you have 3-phase equipment that you need to run on single phase. Not only will that problem be solved, but you'll have the ability for variable speed, soft start, overload protection, and many other features.

I have a 7.5 hp phase converter with a step up transformer to run my 3 phase Bridgeport, metal lathe and radial arm saw. I have been reading about VFD's to power any other 3 phase equipment I might buy. I have been looking on Ebay but I am not sure what specs I should be looking for. I also have a General wood lathe that has a Reeves drive. It is single phase but will not slow down enough for large work like bowls. I have heard that a VFD would be ideal. Again I don't know what to look for. Any advise would be appreciated. Thanks Ted