Crazy rotophase setup

[winnie]

I thought this blast from the past was worth dredging up.

No real question, just a one word comment: wow!

Ersatz single to 3-phase conversion. Massive rotating equipment. What could go wrong?!?

using old motor to transform 240v to 460v ?? - ECN Discussion Forums

 

[Joethemechanic]

Wow sounds like a thread of nothing but bad info

 

[drcampbell]

Wow sounds like a thread of nothing but bad info

That's the working definition of most of the Internet.

 

[Joethemechanic]

That's the working definition of most of the Internet.

200 amp single phase service, all those motors running off it, it was starting to sound like one of those free energy schemes. I was waiting to hear "Tesla" mentioned 25 times, along with atmospheric electricity and vortexes

 

[drcampbell]

Yikes. What a rabbithole.

Hillbillysawmiller seems to have as thorough an understanding of power, energy, electricity, machinery and good safe practices as he has about separating thoughts into paragraphs.

It was written twenty years ago. (almost to the day) I'm quite sure the problem has either been solved by now, or rendered moot by the retirement or death of the Hillbillysawmiller, a catastrophe befalling his sawmill, or cutting all the available timber in the area.

 

[gar]

230502-1143 EDT

I did not try to correlate all the different things in the referenced post.

But if it is a true story, then it makes sense. He stepwise brought different rotating loads on line Each load has some internal loss and therefore a constant load on the power source. If this loss is moderately low, then many of these loads represent a lot of stored rotating mass ( stored energy ). In other words thru his startup procedure he was able to bring a large amount energy into his plant. And store that energy in rotating mass. This energy is then available for short time large peaks.

His sawmill operation is not a continuous load, but rather pulses of load.

It is quite possible that it is a workable system.

.

 

[Jraef]

230502-1143 EDT

I did not try to correlate all the different things in the referenced post.

But if it is a true story, then it makes sense. He stepwise brought different rotating loads on line Each load has some internal loss and therefore a constant load on the power source. If this loss is moderately low, then many of these loads represent a lot of stored rotating mass ( stored energy ). In other words thru his startup procedure he was able to bring a large amount energy into his plant. And store that energy in rotating mass. This energy is then available for short time large peaks.

His sawmill operation is not a continuous load, but rather pulses of load.

It is quite possible that it is a workable system.

.

Yep, that was my take on it too. He’s probably a one man operation, so only one machine gets used at a time, but he leaves everything else running unloaded, so he has basically a rotating reserve. Doable, just kind of wasteful and it would be interesting to know if the utility was metering him for power factor, because it would be horrible. I’m going to guess not, because it’s just a 200A single phase farm service.

 

[Joethemechanic]

I was kinda thinking the stored mechanical energy/induction generator thing. But for an induction generator to deliver power to the line at 60 cycles it should have to be driven over it's synchronous speed by an amount roughly equal to it's slip when functioning as a motor under load

 

[winnie]

An induction machine needs to be driven above synchronous speed to generate in the steady state.

But it can deliver energy back to its supply in transient conditions. That is the 'motor contribution' for short circuit calculations.
And if spinning power can be transferred from one phase to another. That's the whole rotophase concept.

Jon

 

[drcampbell]

... But for an induction generator to deliver power to the line at 60 cycles it should have to be driven over its synchronous speed ...

Is that true for both real and reactive power?

 

[winnie]

An induction generator operating in steady state generally consumes VARs. You still need something to supply the excitation

 

[Joethemechanic]

Is that true for both real and reactive power?

Now this is requiring thought about things I learned over 30 years ago and never used. I can even tell you the book I learned it from, but senility is kicking in.

 

[drcampbell]

An induction generator operating in steady state ...

Nobody's asking about steady-state operation. The question is about a transient condition in which one motor is losing mechanical energy (its spinning reserve) while another motor is starting.

 

[winnie]

Nobody's asking about steady-state operation. The question is about a transient condition in which one motor is losing mechanical energy (its spinning reserve) while another motor is starting.

Sorry, I misread your question about real and reactive power as a steady state question.

The concept of reactive power in a transient is not one I grasp well. In the steady state, reactive power is energy stored in the magnetic field of the motor that is shuttling back and forth with the source.

But in the starting transient, you are building that field in the first place, thus with real net energy transfer.

Short answer: I'd like to know more

 

[electrofelon]

Yikes. What a rabbithole.

Hillbillysawmiller seems to have as thorough an understanding of power, energy, electricity, machinery and good safe practices as he has about separating thoughts into paragraphs.

It was written twenty years ago. (almost to the day) I'm quite sure the problem has either been solved by now, or rendered moot by the retirement or death of the Hillbillysawmiller, a catastrophe befalling his sawmill, or cutting all the available timber in the area.

I don't really see much wrong with it. I thought it was well known you can do this and that the more motors you have on the network the better it works. I'd probably do the same thing if I had a bunch of three phase motors lying around and I had more time than money - but both of those conditions are not the case for me.

 

[drcampbell]

I was referring to the writing, not the installation.

 

[tortuga]

Interesting old find, 20 year old post.
Especially the part about using a old motor as a transformer. I wonder how that would work? some type of Auto-transformer?

Hillbillysawmiller: I would also like to change out the 25 hp motor that I use to generate my 3rd leg with the 40hp that I have on my present saw mill. I believe there is a way to do this without getting another 200 amp service. I remember when I was a kid there was a sawmiller were I grew up who used an old 3 ph motor body to convert 220 3 ph to 460 3 phase. The thing, is I do not know how he had it wired up. I do remember that it was not running and he said it did not pull any juice. In fact I think the rotor had been removed. I can't be sure I was just a kid and the memory is fuzzy. Essentially I think he was using the stator as a transformer to convert the 220v to 460v so that he could run more horse power on less amps. If I could do what he did I could wire all of my motors 460 volt which would give me the ability to add the motors that I need to add and run them from my existing 200 amp service.

Then there is a post further down from a moderator named "resqcapt19" and that mod name sounds really framiliar. :

resqcapt19: The Table 430.150 FLA of all of the motors that he has running at the same time totals 238 amps already.