Considering a 3 phase CNC small lathe - - - have 240V single phase

[awake]

Around here 200 amp service is the usual size for new construction. Part of that is likely due to this area tending to favor all-electric dwellings - heat pumps for HVAC, electric stove, electric water heater, electric clothes dryer ...

 

[MrMetric]

I don't know about the States but here in the U.K. that's quite a hefty service for single phase residential supply. Ours are generally limited to 100 amps. at 240 volts

I believe the U.S. system is centre tapped to earth 120v each side giving a split 120/240v system whereas ours is unipolar with the neutral tied to earth. so I guess your currents may be higher.

I would say that a large number of older homes have 100A panels, or even less. All of the newer homes I've seen have 200A. But remember.... I'm mostly familiar with California. It probably takes 20 hours to drive from the southern to northern boundaries and about 4 to drive across the State. And this is just one State.... There are lots and lots of AHJs out there, and God only knows what you will find!

You are correct about our typical residential power being a center tapped system, with neutral tied to ground (typically to the water main and an alternate ground, usually a 6' rod or rebar embedded in the foundation).

 

[skyline1]

Around here 200 amp service is the usual size for new construction. Part of that is likely due to this area tending to favor all-electric dwellings - heat pumps for HVAC, electric stove, electric water heater, electric clothes dryer ...

With the use of electric cars expected to rise I think this could rise still further and may even lead to 3 phase power becoming standard in homes worldwide. This is probably not the place to debate the pros and cons but electric cars are going to produce a huge, worldwide increase in electrical power demand. This is likely to make 3 phase distribution to individual homes not just more common but in some cases a necessity.

You are correct about our typical residential power being a center tapped system, with neutral tied to ground (typically to the water main and an alternate ground, usually a 6' rod or rebar embedded in the foundation).

I personally think this is a slightly safer system as the maximum fault voltage above earth is 120 volts not 240 volts as in our method.

Best Regards Mark

 

[Steamchick]

Don't get me started on battery electric vehicles... I think it was in the 1870s or 1880s that there were over 1000 battery-electric wagons delivering goods in London... - I guess the same in Washington (I guess they had built it by then?) and New York and Chicago??? Or maybe the US was still at war, or totally on horse-back? (Coal-fired-Steam power for trains and ships is a different story).
But battery electric powered wagons were displaced - for cost and convenience - by oil-burning infernal combustion engines. The US rapidly overtook the rest of the world in this application because they had tar pits and oil readily available.
Horses were only really displaced after the Great War... and the following flu pandemic that was 10 times worse than the current global situation.
Now we are being forced back to batteries...
But the governments of today recognise that "purse-power" of millions of individuals is a strong econimic force, that if harnessed by governments without taxation, can achieve a lot of social objectives and in doing so "popularise" the government. (Did a politician once say "popularity purchases power"?).
I.E. The government does not have the money to build the huge battery storage necessary to level the electical generation by wind and solar against the demands of the power grids... But >20 million vehicles plugged-in to the grid can soak-up >1000MW of surplus generation for use when generation drops... (That's the equivalent of 1 smallish power station.). But the "ignorant masses" (who vote) don't understand so they won't be plugging-in and using their cars as temporary storage of "cheap" electricity for times when there is high demand... And Road haulage (>70% of road fuel usage?) would require the batteries to be charged at night, after we have stopped our daily jobs driving wagons and delivering goods, when there is no solar power on the grid...
But a "bright spark" - intentional pun - did suggest we only need to cover the entire Sahara with solar panels to "generate all the power we need".... (which would change the climate) - "to avoid climate change"...
There is more than enough zinc available on the planet for all the batteries we need, and it doesn't burn in air or water like Lithium...
And current (another pun?) legislation in the 1st world prohibits more than 2 battery cars per trailer for delivering cars to dealers by road or rail transport... Because of the fire-risk!
So what sense is being applied GLOBALLY to resolve all these "highly charged" issues? Nothing I have seen...
And despite regulations for safety, with the best "whit of mankind" we still have disasters with our "best controlled" steam technology = Nuclear power: as in 3-mile island, Chernobyl, the Japanese tsunami Fukushima Daiichi disatser, and many more... So stuffing micro-wave generators next to our brains (mobile phones) and fire-bombs (Lion batteries) in all our offices, workplaces and now cars, will be much safer in future when the shortages on electricity hit home....
Recently, a work colleague told me his son nearly had a breakdown - feeling isolated because he went to stay with family in India, where they only had less than 4 hours electricity per day - and he kept running out of battery power for his phone...
So maybe 200A per household for charging cars is going to be a bit of a problem?
We pay for Government to make sensible decisions to maintain our societies.... and possibly improve a few things? - But just maybe we have never had it so good - and never again will we... and we are all going to die anyway?
On that Electrifying Note (The Note was the battery electric car I worked on for nearly 10 years).
Cheers!
K2

 

[L98fiero]

All you really need is how much input it needs then double it for a three phase motor. You can rope star it or put a pony motor to start it. I ran both my mills that way for years.

I'm running an American Rotary phase converter, when I bought mine they only sold complete packaged units but apparently they now sell the control units separately as well, it has all the capacitors and start/run circuitry and you supply the motor. It's a pretty economical way of doing it. There are probably other companies that sell the control units separately as well.

 

[awake]

On another thread just now I related my experience with putting together an RPC - total cost for me was around $40. I was able to use a scrapped motor that I got from the rubbish bin for free, and was able to get all of the contactors and capacitors I could ever possibly need from the scrap pile of an HVAC business owned by a neighbor. All I had to buy was a couple of momentary push-button switches (to start and stop the RPC) and the twist-lock plug and receptacle. I was a bit apprehensive about building my own, but when I got into it, it proved remarkably easy.

 

[Richard Hed]

On another thread just now I related my experience with putting together an RPC - total cost for me was around $40. I was able to use a scrapped motor that I got from the rubbish bin for free, and was able to get all of the contactors and capacitors I could ever possibly need from the scrap pile of an HVAC business owned by a neighbor. All I had to buy was a couple of momentary push-button switches (to start and stop the RPC) and the twist-lock plug and receptacle. I was a bit apprehensive about building my own, but when I got into it, it proved remarkably easy.

Can you show us the circuitry and plans?

 

[ajoeiam]

With the use of electric cars expected to rise I think this could rise still further and may even lead to 3 phase power becoming standard in homes worldwide. This is probably not the place to debate the pros and cons but electric cars are going to produce a huge, worldwide increase in electrical power demand. This is likely to make 3 phase distribution to individual homes not just more common but in some cases a necessity.

I don't see this happening!
Somewhat locally we generate a LOT of hydro power - - - - enough to export to a number of the neighboring jurisdictions in fact. Even with that it is incredibly difficult to get a connection to 3 phase power - - - - even if its running right by - - - - and when its not - - - - - think $100k per post - - - - so my cost would be somewhat around $2M and even if I dropped the cash on the table it wouldn't get built because I just wouldn't use enough juice.

IMO a far better idea would be for rural clients to go off grid - - - - over 20 years could even reduce power costs!

 

[Richard Hed]

I don't see this happening!
Somewhat locally we generate a LOT of hydro power - - - - enough to export to a number of the neighboring jurisdictions in fact. Even with that it is incredibly difficult to get a connection to 3 phase power - - - - even if its running right by - - - - and when its not - - - - - think $100k per post - - - - so my cost would be somewhat around $2M and even if I dropped the cash on the table it wouldn't get built because I just wouldn't use enough juice.

IMO a far better idea would be for rural clients to go off grid - - - - over 20 years could even reduce power costs!

Here in the Soviet of Washington we have PUDs, which if you aren't familiar witht he term means Public Utility District. The PUDs are actually owned by the local public. So theoretically this means we should be getting very cheap power. HOwever, that is a lot of bullkrap. It doesn't work out that way at all. Since we sell power to primarily California, and many other states as well, this raises the price to the "owners" as well. It goes to show that sneaky sleight of hand is being practiced. Back in the 90's, our local PUD had 1B$ surplus--what is a PUD doing with surplus $$? It should be ONLY charging enough $$ to service the dams, lines, transformers, etc + or - a bit for fluctuations in need (e.g. power lines down due to storms). The Feds found out about it and forced Grant County to use the $$ or give it back. so what did GRANT PUD do? They put in a glass line for internet (fibre optics) which was supposed to be really cheap for the users. Well, the first year was cheap and very few users. The second year the prices to use the glass lines doubled and the numver of users had gone WAY up. What kind of game is this? It's called pull the wool over the sheep's eyes!

Anything that is government means endless manipulation and opportunity to lie and shear. In the end, the PUD had bought some extremely expensive electronics to go with the glass line installations. HOwever, since the public had not fallen for the trix, they went unused. The things were sold at publick auction. They had a going price of $300 each, were about 5" long X 3" wide and half inch deep. There were about 3-400 on a pallet at the auction. The pallet went for $300. There were many pallets. The guys who won the bids sold the pieces for $15 online. So the 1B$ was disposed of, clearly a losing method to use the public's $$, other than the fact that we ended up with relatively expensive but very fast internet. (This of course was 1999's $$ not today's $$)

If California is out of power, then it really means California is too dense for the energy, water and other resource usage. They cannot DEMAND that the Soviet send them more power, which they seem to do. Oddly enough, Seattle has been putting up their own power grids using wind power generators that seem to be working very well. It is a Seattle PUD. I thimpfk there are some manipulations and sheep shearing going on there as well, but am not sure because I am not directly concerned with that.

Anyway, my point is that 3PH should be generated by the VFD devices and just forget about the expensive 3PH lines. ONe of the reasons I am making steam engines is indeed, for the eventual production of electric generation. If I can do a 10HP or so, I can generate power enough for home and shop and not have to deal with liars, cheats, fraudulators, and other government and private entities.

 

[ddmckee54]

At 10HP your boiler is going to be big enough that you'll still have to deal with the government in the form of boiler inspectors. Any boiler small enough the slip under the inspection requirements won't be big enough to power 10HP - at least not long enough to accomplish anything useful.

Don

 

[awake]

Can you show us the circuitry and plans?

Plans? What is this thing you are speaking of?



Ordinarily I do work up a schematic / plans / etc. before undertaking any project, so as to have a record of what I have done if for no other reason. Unfortunately, in this case, I did not. I made use of plans and writeups on the internet; the two that I recall being particularly helpful were by Matt Isserstedt and by Fitch Williams. If you search for either of those names together with "Rotary Converter" you will quickly find links to downloadable .pdf files. As I recall, my design was somewhat different and somewhat simpler than either of theirs, but definitely drew on what I learned from them:

I started with a 240 to 24v transformer, a 2 pole contactor, and a 4 pole contactor scavenged from the HVAC scrap pile. 240v comes in from the supply and is wired into the transformer to provide 24v control voltage.

The 24v is routed in sequence through two momentary push button switches, first an NC switch (the STOP button) and then an NO switch (the START button). The output from the NO switch is directed to the coil on both of the contactors; when the NO button is pressed, both contactors activate.

The 4P contactor can be called the RUN contactor. 2 of the poles of this contactor are wired to the two legs of the 240v; when the RUN contactor is activated, it connects 240V to two of the three legs of the motor.

The other two poles of the 4P RUN contactor are used to "latch" the contactor. They are connected to the 24v control voltage coming out of the NC STOP button. (Note that this is tapping into the 24v after the STOP switch but before the START switch.) When the contactor is activated, this 24v control is fed back into its own coil, keeping the contactor activated until the STOP switch is pressed. Make sure to match the polarity of the 24vac.

The 2P contactor can be called the START contactor. Its only function is to switch a start capacitor into the circuit. One leg of the 240V fed into the motor is also fed to a pole of the 2P contactor. When the contactor is activated, it connects a start capacitor between this leg and the third leg of the motor.

So the sequence goes like this: Press the START (NO) button, activating both contactors; this allows 240V to flow to two legs of the motor (through the RUN contactor), and also connects the third leg to a start capacitor. Once the motor spins up (which takes < 1 second), the START switch is released; this allows the START contactor to deactivate, disconnecting the start capacitor from the circuit. However, the RUN contactor remains activated, latched by feeding itself 24v, so the motor continues to run. At this point, the motor is running on 2 legs, and the spinning of the motor is generating the 3rd leg.

To shut it down, press the STOP button. This breaks the latching circuit, allowing the RUN capacitor to deactivate; the 240V is disconnected from the motor, and the latching feedback circuit is also disconnected.

According to most things I read, I should have also wired in some run capacitors to balance the 3 legs of the resulting 3-phase. However, I did read a few things that suggested that might not be necessary. When I checked the voltages on the 3 legs, they were suprisingly close, and I decided not to fool around with run capacitors. (I don't remember whether I checked the voltages with the mill powered on or not - or which way one should check the voltages.) The RPC and the mill it powers have both run flawlessly for many years now.

 

[awake]

At 10HP your boiler is going to be big enough that you'll still have to deal with the government in the form of boiler inspectors. Any boiler small enough the slip under the inspection requirements won't be big enough to power 10HP - at least not long enough to accomplish anything useful.

Don

Don, I am not seeing where a boiler came into the discussion - that may just mean I missed it somewhere in the last 5 pages! But also wondered if perhaps this post was intended for a different thread ... ??

 

[Richard Hed]

At 10HP your boiler is going to be big enough that you'll still have to deal with the government in the form of boiler inspectors. Any boiler small enough the slip under the inspection requirements won't be big enough to power 10HP - at least not long enough to accomplish anything useful.

Don

Absolutely

 

[Richard Hed]

Plans? What is this thing you are speaking of?



Ordinarily I do work up a schematic / plans / etc. before undertaking any project, so as to have a record of what I have done if for no other reason. Unfortunately, in this case, I did not. I made use of plans and writeups on the internet; the two that I recall being particularly helpful were by Matt Isserstedt and by Fitch Williams. If you search for either of those names together with "Rotary Converter" you will quickly find links to downloadable .pdf files. As I recall, my design was somewhat different and somewhat simpler than either of theirs, but definitely drew on what I learned from them:

I started with a 240 to 24v transformer, a 2 pole contactor, and a 4 pole contactor scavenged from the HVAC scrap pile. 240v comes in from the supply and is wired into the transformer to provide 24v control voltage.

The 24v is routed in sequence through two momentary push button switches, first an NC switch (the STOP button) and then an NO switch (the START button). The output from the NO switch is directed to the coil on both of the contactors; when the NO button is pressed, both contactors activate.

The 4P contactor can be called the RUN contactor. 2 of the poles of this contactor are wired to the two legs of the 240v; when the RUN contactor is activated, it connects 240V to two of the three legs of the motor.

The other two poles of the 4P RUN contactor are used to "latch" the contactor. They are connected to the 24v control voltage coming out of the NC STOP button. (Note that this is tapping into the 24v after the STOP switch but before the START switch.) When the contactor is activated, this 24v control is fed back into its own coil, keeping the contactor activated until the STOP switch is pressed. Make sure to match the polarity of the 24vac.

The 2P contactor can be called the START contactor. Its only function is to switch a start capacitor into the circuit. One leg of the 240V fed into the motor is also fed to a pole of the 2P contactor. When the contactor is activated, it connects a start capacitor between this leg and the third leg of the motor.

So the sequence goes like this: Press the START (NO) button, activating both contactors; this allows 240V to flow to two legs of the motor (through the RUN contactor), and also connects the third leg to a start capacitor. Once the motor spins up (which takes < 1 second), the START switch is released; this allows the START contactor to deactivate, disconnecting the start capacitor from the circuit. However, the RUN contactor remains activated, latched by feeding itself 24v, so the motor continues to run. At this point, the motor is running on 2 legs, and the spinning of the motor is generating the 3rd leg.

To shut it down, press the STOP button. This breaks the latching circuit, allowing the RUN capacitor to deactivate; the 240V is disconnected from the motor, and the latching feedback circuit is also disconnected.

According to most things I read, I should have also wired in some run capacitors to balance the 3 legs of the resulting 3-phase. However, I did read a few things that suggested that might not be necessary. When I checked the voltages on the 3 legs, they were suprisingly close, and I decided not to fool around with run capacitors. (I don't remember whether I checked the voltages with the mill powered on or not - or which way one should check the voltages.) The RPC and the mill it powers have both run flawlessly for many years now.

Altho' your explanation covers most everything if not all, visual circuit is a lot easier to read and follow. That's all I was trygint to get at.

 

[Richard Hed]

Don, I am not seeing where a boiler came into the discussion - that may just mean I missed it somewhere in the last 5 pages! But also wondered if perhaps this post was intended for a different thread ... ??

It was I who mentioned I want to build a large enough sized steam engine to power my house and shop. That would be up to 10 HP thus necessitating a boiler large enough to feed it. that was after my rant about the PUDs and goverment "games".

 

[Steamchick]

I guess there is something in the depths of this discussion that I have missed. Andy (Awake), please can you explain an odd bit: Do you use the 3 phases from the rotary converter to power a VFD for the 3-phase motor for the lathe? I would have simply bought a VFD with single phase input with 3-phase output and missed-out the rotary converter - which suggests I have missed something important in this thread?
Ta,
K2

 

[giel]

here in the Netherlands every home has 3 phase 60 amp coming into the fuse box, usually there is only 1 phase connected to the fusebox but if you pay 60 euro's they connect all 3 and you are having industrial power. other way around this is using a frequecy controller (costs about 300€ for a 2kw version) this makes 3 phase output from a single phase and has soft start so the peak starting power is avoided

 

[awake]

Altho' your explanation covers most everything if not all, visual circuit is a lot easier to read and follow. That's all I was trygint to get at.

Yes, I hear you. Ordinarily I would have worked up a schematic in KiCAD, but when I checked my computer files, there was simply an empty folder under RPC. Apparently I went with BOTE engineering on this one. (Back Of The Envelope)

I have attached a hand-drawn schematic, but only on the condition that you promise not to laugh. I don't have the foggiest idea what the correct convention is for drawing a contactor, and not too sure about some of the other components either. I do not include a value for the start capacitor, as I would have to disassemble the enclosure to see what I wound up using. But I am 99% sure I went with the recommendation from one or the other of the two .pdf files that I mentioned previously to calculate the size to use, and it worked perfectly. Obviously, there is plenty of room for improvement, but this simple circuit has served me well for a long time.

It was I who mentioned I want to build a large enough sized steam engine to power my house and shop. That would be up to 10 HP thus necessitating a boiler large enough to feed it. that was after my rant about the PUDs and goverment "games".

Ah, sorry - somehow I missed that in that post. Don, my apologies!!

I guess there is something in the depths of this discussion that I have missed. Andy (Awake), please can you explain an odd bit: Do you use the 3 phases from the rotary converter to power a VFD for the 3-phase motor for the lathe? I would have simply bought a VFD with single phase input with 3-phase output and missed-out the rotary converter - which suggests I have missed something important in this thread?
Ta,
K2

No, I use the 3-phase from the rotary converter to power my mill - no VFD's involved. As you say, there would be no reason for the RPC if I were using a VFD.

I would certainly agree that a basic BP-type mill is a really good candidate for a VFD, since the only thing that needs power is the one motor. It would be even more compelling if the mill uses step pulleys, as the VFD would allow speed adjustment without moving the belts - albeit with some loss of torque at the slower speeds. In my case, however, my mill has the 2J variable speed head on it; it was noisy when I bought it, but that is simply par for the course; the rebuild was easy, and now I have infinite speeds from 60 - 3100 rpm with no loss of torque. Thus, speed control was not a motivation for me to go with a VFD ... and when I did all of this, there was not the ready supply of cheap VFDs that we have today. Going with a $40 RPC was therefore an easy decision for me!

If it comes to a CNC or such machine, the decision might be more complicated. How many 3-phase motors are involved? How are the controls wired - do they take a 3-phase input, or do they require separate single-phase power? My understanding is that a VFD has to be wired directly to a single motor, so I could see someone deciding to go with an RPC instead for the convenience of powering the whole unit.

In the case of Brian's new DoAll contour saw (band saw), the complicating factor is the built-in blade welder. I've only had experience with one similar saw, but on that one, there is a single 3-phase power lead, which powers both the saw motor and the blade welder. That saw had infinite speed control, so once again, a VFD is not needed for that purpose ... and I don't think (?) a VFD would work to power the welder.

 

[ddmckee54]

We're talking about the blade welder on the bandsaw, right? As small as that welder would be, I doubt that it's 3 phase to begin with. The bandsaw was originally 240V 3 phase. That would be 240V from phase A to B, phase B to C, or phase A to C - as in 240V single phase. They probably just used the guts of a 240V single phase welder, instead of a more complicated and more expensive 3 phase welder. Chase down the power wiring to the welder. If it's only got 2 power conductors to it then it's single phase. In that case the welder could be run directly off the 240V single phase input power.

If the welder is 3 phase, it might or might not tolerate the VFD's output, some stuff will and some won't. It's a crapshoot trying to figure out what'll work and what won't. I can tell you for a fact that Baldor motors, with the built in brake that's wired between 2 of the motor legs, will not work. The motors tolerate the VFD just fine, but the brakes refuse to release. We wound up installing separate brake contactors and wiring the brakes separately.

Don

 

[Courierdog]

In Canada having 3 phase wiring is strictly a commercial or industrial option.
While the 2 phase wiring is standard for residential. This allows 110 volt single phase and 220 volt two phase appliances.
Having used single phase, two phase and three phase wiring there are advantages to each.