3 phase converter help

Michaeljp86 said:
For my lathe I bought a static converter to run it on 220V single phase. Ive read that with a static converter you only get about 2/3 of the hp that the motor would make on 3 phase because it only adds the 3rd leg to get the motor spinning after that the motor is only on 2 legs.

I did some work at a machine shop that only had single phase power and he would start up a 3 phase machine to make 3 phase power. So to use lets say a lathe he would fire up a mill off the static converter and the motor would act as a generator on the 3rd leg. So on his lathe he would have power on all 3 legs all the time.

Ive been reading and watching youtube videos and this looks like how a rotary converter works, just a static converter starting a motor. So I was wondering, couldn't I find a 3phase motor and start it off the static converter and then have 3 power legs to the lathe?

The reason I ask is my lathe seem to weak, I cant run it at higher speeds.
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the answer to your question is yes. take a 3 phase motor and if you want it to SELF START use a static converter to start it and it will make 3 phase power for your lathe and other machines as well if you want. that is the way i'm doing it. use to spin it to get it going but got tired of that
 
Good Morning all, My brother and I did just that, we had a 5hp GE motor that turned 3450 RPM I think, bought a ststic phase converter to start it no caps for balance or the like and it works great, later on I got a metal box form lowes and made a distrubition panel and wired up all our machines to it, theres nothing special to it not rocket science, good luck to all, DW:think1:
 
Guys I am not condoning anyone's actions, but please lets not let this deteriorate further. perhaps chalk it up as a bad day? Your cooperation in this matter is much appreciated.

Lets continue helping each other.

Steve
 
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Michaeljp86 said:
Do these make true 3 phase power? Ive seen some nice welding equipment thats 3 phase but I heard they wont work right on a converter because its not true 3 phase.
Click to expand...

My opinion ...

Do they make "true 3 phase power"? I think that depends on your definition of "True". I am not trying to be a smart a.. but just suggesting you need to consider what you are going to use it for and how "true" it needs to be.

Each phase the utility company provides is a 60Hz sinusoidal wave and the three phases are 120 degrees apart, so we will call that "true 3 phase power".

What comes into most homes in the US is known as 3-wire, single phase, midpoint neutral and is usually derived by putting a transformer across one of the three phases.

First step in the search for an answer what a VFD actually does create is to understand how the VFD works. If you look at a block diagram the first block takes the AC input and converst it to DC. This is a relatively simple process and it is very easy to make it "input agnostic". Many of the VFD's can take either single phase or three phase as input the VFD can't tell the difference.

The next block in the diagram is the "generate the waveform" block. This is were modern electronics come into play. At the heart of it is a computer controlled "wave form generator" ... a digital synthesizer if you will ... and as such could generate just about any wave form(s) you could think of in as many phases you might like. In a VFD the wave form generator computer code has been specialized to focus on generating three sinusoidal waves 120 degrees apart just like what the power company delivers.

The wave form generator then feeds to the "power" stage ... the "D" part of the name ... where all of that DC that was created earlier is attached to the load ... in your case a motor ... with the power stage being driven by the wave form generator. Think of a component audio system where there are receivers, players, etc. feeding a pre-amp when then feeds the power amp which is connected to the speakers.

Depending on what the actual load is, the wave form generator and the associated power stage do a very good job of synthesizing the three phase power that the utility company would provide, to the point of the motor not actually knowing the difference.

As long as the output is under complete computer control there are a couple of other things the VFD can also do without breaking a sweat ... like vary the frequency of the output ... the "VF" part of the name ... from 0Hz to 120Hz which will vary speed of the motor and why you might feed three phase input into a VFD to then run a phase motor at various speeds ... like actually monitor the output to see how well the output of the power stage and the motor are getting along and make real time adjustments to the wave form to make sure the system is behaving as the user has said it is suppose to ... like modify the wave form to assist in starting ... like redirecting the output that comes back from the motor when the system is asked to stop causing the motor to stop rotating much more quickly than if left on its own ... like define the acceleration and deceleration characteristics of the motor to meet specific needs ... like drive the user nuts trying to set up as many as a hundred parameters if the user wants to really fine tune the darn thing ... but I digress.

I think that the power stage of the VFD has been fine tuned to work with the electrical characteristics of an electric motor. As such a welder may not present the correct type of load to work well. If it is a transformer based welder the combination might work as the load is an inductive load but you would not be able to use the variable frequency part of the VFD as the transformer is designed for a specific frequency and looses efficiency when other frequencies are applied. In short not a good VFD ROI. If it is an inverter based welder then I would think that it would already be able to take multiple kinds of inputs as it is doing the same thing the VFD is doing ... taking a plethora of inputs and converting it to DC ... the inverter part of the welder definition ... and then letting computers do their magic ... so again not a good ROI.

Just my opinion,
Arvid
 
arvidj said:
My opinion ...

Do they make "true 3 phase power"? I think that depends on your definition of "True". I am not trying to be a smart a.. but just suggesting you need to consider what you are going to use it for and how "true" it needs to be.

Each phase the utility company provides is a 60Hz sinusoidal wave and the three phases are 120 degrees apart, so we will call that "true 3 phase power".

What comes into most homes in the US is known as 3-wire, single phase, midpoint neutral and is usually derived by putting a transformer across one of the three phases.

First step in the search for an answer what a VFD actually does create is to understand how the VFD works. If you look at a block diagram the first block takes the AC input and converst it to DC. This is a relatively simple process and it is very easy to make it "input agnostic". Many of the VFD's can take either single phase or three phase as input the VFD can't tell the difference.

The next block in the diagram is the "generate the waveform" block. This is were modern electronics come into play. At the heart of it is a computer controlled "wave form generator" ... a digital synthesizer if you will ... and as such could generate just about any wave form(s) you could think of in as many phases you might like. In a VFD the wave form generator computer code has been specialized to focus on generating three sinusoidal waves 120 degrees apart just like what the power company delivers.

The wave form generator then feeds to the "power" stage ... the "D" part of the name ... where all of that DC that was created earlier is attached to the load ... in your case a motor ... with the power stage being driven by the wave form generator. Think of a component audio system where there are receivers, players, etc. feeding a pre-amp when then feeds the power amp which is connected to the speakers.

Depending on what the actual load is, the wave form generator and the associated power stage do a very good job of synthesizing the three phase power that the utility company would provide, to the point of the motor not actually knowing the difference.

As long as the output is under complete computer control there are a couple of other things the VFD can also do without breaking a sweat ... like vary the frequency of the output ... the "VF" part of the name ... from 0Hz to 120Hz which will vary speed of the motor and why you might feed three phase input into a VFD to then run a phase motor at various speeds ... like actually monitor the output to see how well the output of the power stage and the motor are getting along and make real time adjustments to the wave form to make sure the system is behaving as the user has said it is suppose to ... like modify the wave form to assist in starting ... like redirecting the output that comes back from the motor when the system is asked to stop causing the motor to stop rotating much more quickly than if left on its own ... like define the acceleration and deceleration characteristics of the motor to meet specific needs ... like drive the user nuts trying to set up as many as a hundred parameters if the user wants to really fine tune the darn thing ... but I digress.

I think that the power stage of the VFD has been fine tuned to work with the electrical characteristics of an electric motor. As such a welder may not present the correct type of load to work well. If it is a transformer based welder the combination might work as the load is an inductive load but you would not be able to use the variable frequency part of the VFD as the transformer is designed for a specific frequency and looses efficiency when other frequencies are applied. In short not a good VFD ROI. If it is an inverter based welder then I would think that it would already be able to take multiple kinds of inputs as it is doing the same thing the VFD is doing ... taking a plethora of inputs and converting it to DC ... the inverter part of the welder definition ... and then letting computers do their magic ... so again not a good ROI.

Just my opinion,
Arvid
Click to expand...

That was a lot of good info, my dad is a electrician and Ive worked with him many years. The phase converters we have worked on were either rotary or static and ran motors.

My ideal setup would be to have 3 phase wired in the building where I add whatever I want instead of having to add some sort of converter to everything you buy. I could have that with a rotary converter but from what Im told by people trying to run things like welders they rotary converts don't work. I guess some welders will work but they wont work like they should and that's because the 3 legs are not balanced.


Ive never really dealt with a VFD before other then the one me and my dad mounted for a speed control on the conveyer at a apple farm. The ones Kennyd posted are not as over priced as I figured they would be.

So i guess I don't really have a option of making 3 phase power to run welders or plasma cutters. So I should either make a rotary converter or get one of these VFD gizmos.
 
Michaeljp86 said:
So i guess I don't really have a option of making 3 phase power to run welders or plasma cutters. So I should either make a rotary converter or get one of these VFD gizmos.
Click to expand...

Yeah, running welders or other fancy electronic equipment is not what VFD's are for, or RPC's in my opinion. The advantage of a VFD or a RPC (for motors) is they are very energy efficient, quiet, compact, and can add variable speed to the piece of equipment its powering. They are very reasonably priced if the motor is under 3 horsepower, over 3HP they start to get pricey.
 
Kennyd said:
Yeah, running welders or other fancy electronic equipment is not what VFD's are for, or RPC's in my opinion. The advantage of a VFD or a RPC (for motors) is they are very energy efficient, quiet, compact, and can add variable speed to the piece of equipment its powering. They are very reasonably priced if the motor is under 3 horsepower, over 3HP they start to get pricey.
Click to expand...

Ill probably end up going that route. I can probably get $50 on ebay for my static converter. Since I probably wont end up with more machines for a while.
 
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