Anyone Else Outraged About 3 Phase?

[drussell]

Oh I did not know about the VFD with boost.. interesting piece of kit.

What are good brand VFD? I need maybe need a VFD from 240VAC 60HZ to 240 50HZ, 3KW.
BTW, do I really need the 50Hz or VFD? I mean a 50Hz motor will get in trouble if I feed it with 60Hz?

One of the major advantages of using a VFD is the speed control, so the input frequency that the motor is expecting doesn't really matter, you can generate whatever you want.  That's the beauty of a VFD and the whole point!

This all ties in with the things I'm talking about at the car wash, I would like to soft-start the 3HP 3-phase (208-240V motors) high pressure pumps.  Well I'd like to soft-start pretty much everything there that is a big 3-phase motor.

I'll try to edit up some video clips later today if I can find the time!

[drussell]

I mean a 50Hz motor will get in trouble if I feed it with 60Hz?

Many motors will run fine on the "wrong" frequency (won't burn up or something) but the speed will be different due to the different input frequency.  Many motors do explicitly state on the rating plate the speeds that they will run on 50 Hz vs 60 Hz....

[Cerebus]

One of the major advantages of using a VFD is the speed control, so the input frequency that the motor is expecting doesn't really matter, you can generate whatever you want.  That's the beauty of a VFD and the whole point!

And of course with the ascendency of VFDs and active motor control in general people tend to have stopped thinking in terms of fixed speed synchronous motors that are designed with a specific mains frequency in mind and more in terms of a general synchronous motor (usually a permanent magnet motor until you start getting really big) that can operate across a significant range of frequencies and speeds.

Of course there are a lot of fixed speed synchronous direct mains connected motors out there, but as they come up for replacement it's highly likely that the replacement is going to involve active control (aka a VFD).

[mag_therm]

6 different lines? You'd never see such a thing.

For rectifier transformers, 6 phases are needed above about 1500 kW to meet harmonic content standards.
Above about 3000 kW,  12 phases are needed.
6 phases are obtained on the secondaries of one tranformer with 3 phase input.
12 phases are usually obtained by using two transformers, each with a zig-zag 3 phase primary. +/- 7.5 degrees.   

[JohnG]

It should just be DC all the way, baby  .

Just kidding, the safety issues alone would give me nightmares.

I have 200A, 240VAC single phase in the NE US. Most of my area started at 60A through the 1950s, 100A in the 1960s, and now 200A seems to be the standard, since you need to power those air conditioners. It cost me about $1000 USD to upgrade from 100A to 200A, and this included the cable from the power head to the breaker box, a new, much larger breaker box, and installation.

There are a lot of advantages to 3-phase in industry, but in the US, the rediential single phase system is in place, and the main reason for three phase, motors, is rapidly going away due to the low cost of VFDs. These provide huge advantages to motors (variable speed, all kinds of protection, etc.). And many appliances have already moved to this combination (BLDC is essentially the same system) because of these benefits. My clothes washer, dishwasher, fridge, and AC units all have VFDs of some sort. They can be really, really cheap as part of a custom appliance control system, and they let you use a cheaper motor. I recently replaced a 16 year old clothes washer, and the old one had a VFD, which still worked (the failure was an aluminum bearing strut).

Since the advent of three-phase VFDs, I quit thinking about 3-phase for my house.

John

[drussell]

Since the advent of three-phase VFDs, I quit thinking about 3-phase for my house.

Yup....  Pretty much the only reason you would have ever wanted to have real three phase at home would be to run some large motor, but now a VFD makes that easy anyway, regardless of the input.

[Berni]

Yep 50Hz or 60Hz doesn't really matter for a motor. It simply runs a bit faster on 60Hz . You can even use a VFD to put 100Hz into such a motor to get it going even faster, but the torque becomes limited because there is not enough voltage to push as much current trough the motor.

As for a VFD shifting voltage up, that is not a problem. Any big VFD needs to have a PFC input in order to not polute the mains input with tons of harmonics. This active PFC is simply a rectifier followed by a boost converter that boosts the lower parts of the sinewave up in order to let it use power troughout the entire sine wave cycle rather than just at the sine peaks that a typical rectifier and capacitor would do. To get more voltage on the DC bus this boost converter simply needs to be designed to boost it up even higher.

BLDC motors are indeed the best kind of motor design in terms of performance, the permanent magnets bringing there own field in them make the work of the stators electromagnets easier and so give a more powerful motor in a smaller and lighter form factor. The VFDs required to run this versus 3 phase async is pretty much the same apart from slight algorythem changes. But there will still be cases where they just don't care about any soft start or fancy speed control, the sort of stuff where they just want a blower fan to push some air when they flip a switch, for that the simple and reliable asynchronus motor is just fine. Tesla knew what he was doing.

[madires]

I fully agree, a single phase would work fine for most households. The difference is where the loads of the 3-phase grid are balanced. In some countries the loads are balanced via the pole transformers or flats/homes, while in other countries the loads are balanced in each flat's distribution panel.

[Zucca]

Reason I am asking is maybe I will move to US, and I have all my tools/equipment from EU I want to use in USA.
The plan is to rewire the US home taking the 240VAC 60HZ into a 40A European RCD on a separate EU panel and install some german schuko plugs in my future home.
VFD is nice but I think I will not bother to power my EU stuff.

I personally like much more the european 240VAC plugs and grid network components.
Nothing can beat a IEC 60309.. The blue ones, I love them... and I will install somel in my future USA garage for sure.

The US plugs are poorly designed in my eyes.

PS: I lived already in USA and one day the lights were acting funny, I measured the main and I was getting 230VAC in the 110VAC ones. Probably some street trafo went kaboom...
Some little switching PSUs melted but thank God nothing big was on during the grid malfunction.
My home will have something if vmain> 140VAC or so then cut the power, thank you and goodbye.

[langwadt]

Since the advent of three-phase VFDs, I quit thinking about 3-phase for my house.

Yup....  Pretty much the only reason you would have ever wanted to have real three phase at home would be to run some large motor, but now a VFD makes that easy anyway, regardless of the input.

for a VFD it can also be an advantage with three phases input making it easier to rectify to the DC bus voltage

[drussell]

For rectifier transformers, 6 phases are needed above about 1500 kW to meet harmonic content standards.
Above about 3000 kW,  12 phases are needed.

Wait... What?!

I thought we were mostly talking about the need (or want) for residential three-phase...

If you need 3 megawatts to your garage, what kind of time machine are you developing in there?   

Do tell!  I may find your ideas intriguing and wish to subscribe to your newsletter!

[mag_therm]

For rectifier transformers, 6 phases are needed above about 1500 kW to meet harmonic content standards.
Above about 3000 kW,  12 phases are needed.

Wait... What?!

I thought we were mostly talking about the need (or want) for residential three-phase...

If you need 3 megawatts to your garage, what kind of time machine are you developing in there?   

Do tell!  I may find your ideas intriguing and wish to subscribe to your newsletter!

I am sorry that I seem to have offended you, but if you read the post of drussell that I snipped ( perhaps too much), you will see that he was referring to 7kV and 13 kV distribution which is right at the level where the transformers I mentioned, are used.
And the reason the 6 phase etc is used, is that it is a practical way of keeping distortion low on those distribution levels.

[drussell]

For rectifier transformers, 6 phases are needed above about 1500 kW to meet harmonic content standards.
Above about 3000 kW,  12 phases are needed.

Wait... What?!

I thought we were mostly talking about the need (or want) for residential three-phase...

If you need 3 megawatts to your garage, what kind of time machine are you developing in there?   

Do tell!  I may find your ideas intriguing and wish to subscribe to your newsletter!

I am sorry that I seem to have offended you, but if you read the post of drussell that I snipped ( perhaps too much), you will see that he was referring to 7kV and 13 kV distribution which is right at the level where the transformers I mentioned, are used.
And the reason the 6 phase etc is used, is that it is a practical way of keeping distortion low on those distribution levels.

Heh...  not offended in any way, of course...  I just should have added a at the end.  Haha

't'was tongue-in-cheek...   

Darn, so you're not developing a time machine?  Awwww....   

[mag_therm]

All OK,
I think has been a good thread and interesting to read the comments from a diverse group of experiences.

[David Hess]

It has a lot to do with zoning of your area and the infrastructure that is in place. Residential areas don't need 3 phase so it's not part of the infrastructure. Why add that extra cost to a zone if 3 phase probably won't be used. I don't know which part of the country your in but there are also City bylaws and Provincial laws that  prevent industrial activity in residential zones. If you live outside a city limit then you should have no problem getting 3 phase installed . Or if you live in an older community like mine that has 3 phase from past industrial services . But even here it's slower being removed because it's not used anymore.

Where i have lived, 3-phase is on the power poles, with periodic transformers converting one of the phases to isolated split phase, but zoning regulation forbid providing 3-phase to homes specifically to prevent the use of "industrial" machinery in residential areas.

[Berni]

Where i have lived, 3-phase is on the power poles, with periodic transformers converting one of the phases to isolated split phase, but zoning regulation forbid providing 3-phase to homes specifically to prevent the use of "industrial" machinery in residential areas.

Then the guy with a rotary converter has the last laugh at the paper pushing idiots.

[langwadt]

Where i have lived, 3-phase is on the power poles, with periodic transformers converting one of the phases to isolated split phase, but zoning regulation forbid providing 3-phase to homes specifically to prevent the use of "industrial" machinery in residential areas.

Then the guy with a rotary converter has the last laugh at the paper pushing idiots.

need some way to turn that pesky electricity into noise and heat

[HB9EVI]

Where i have lived, 3-phase is on the power poles, with periodic transformers converting one of the phases to isolated split phase, but zoning regulation forbid providing 3-phase to homes specifically to prevent the use of "industrial" machinery in residential areas.

strange attitude. in Switzerland the entire low-voltage network delivers 3ph to the houses; even the 400 year old stone hut in the southern alps where I lived over 10 years had 3ph fused at 25A each; I was glad to have it since it allowed me to use a 3ph wood chopper without the need to rebuild or a VFD. Most higher power household appliances like stoves or wash driers run on 380V here.
although I didn't wire up my lab with 3ph; I had it in my old QTH, but actually never really used it.

[David Hess]

Where i have lived, 3-phase is on the power poles, with periodic transformers converting one of the phases to isolated split phase, but zoning regulation forbid providing 3-phase to homes specifically to prevent the use of "industrial" machinery in residential areas.

Then the guy with a rotary converter has the last laugh at the paper pushing idiots.

He only laughs up to the point where a neighbor files a complaint and the paper pushing idiots start harassing him for "running a business" at his home.  And somewhere behind those paper pushing idiots are more idiots with guns.

[james_s]

Where i have lived, 3-phase is on the power poles, with periodic transformers converting one of the phases to isolated split phase, but zoning regulation forbid providing 3-phase to homes specifically to prevent the use of "industrial" machinery in residential areas.

strange attitude. in Switzerland the entire low-voltage network delivers 3ph to the houses; even the 400 year old stone hut in the southern alps where I lived over 10 years had 3ph fused at 25A each; I was glad to have it since it allowed me to use a 3ph wood chopper without the need to rebuild or a VFD. Most higher power household appliances like stoves or wash driers run on 380V here.
although I didn't wire up my lab with 3ph; I had it in my old QTH, but actually never really used it.

Well if you're looking for logic in politics you are bound to be disappointed. It's very common to have people legislating on things they know little or nothing about. The person or group who decided to ban 3 phase to residential units in that area probably had no idea that rotary converters or VFDs existed and thought that the proposal was a perfectly reasonable way to prevent something viewed as undesirable. A knowledgeable person is just going to be frustrated trying to make sense of it.

[james_s]

Reason I am asking is maybe I will move to US, and I have all my tools/equipment from EU I want to use in USA.
The plan is to rewire the US home taking the 240VAC 60HZ into a 40A European RCD on a separate EU panel and install some german schuko plugs in my future home.
VFD is nice but I think I will not bother to power my EU stuff.

I personally like much more the european 240VAC plugs and grid network components.
Nothing can beat a IEC 60309.. The blue ones, I love them... and I will install somel in my future USA garage for sure.

The US plugs are poorly designed in my eyes.

PS: I lived already in USA and one day the lights were acting funny, I measured the main and I was getting 230VAC in the 110VAC ones. Probably some street trafo went kaboom...
Some little switching PSU melted but thank God nothing big was on during the grip malfunction.
My home will have something if vmain> 140VAC or so then cut the power, thank you and goodbye.

I don't think it's legal to do what you propose, however I don't think anyone is likely to come hassle you about it either. I've thought it would be amusing to install a UK socket in my den/office/project room fed by a 240V 50Hz inverter in the garage but instead I've just set up something on the bench when I need 50Hz power for something.

I suspect what happened was you lost the neutral in the panel resulting in the two legs of 120V branch circuits being in series. It happened to my grandmother's house once when a direct lightning strike to the pole in her yard vaporized the neutral conductor in the meter base which was out on that pole. Occasionally it happens due to damaged or improperly installed connections in the breaker panel but it's rare. If you have decent quality gear that is properly installed and not abused it's a very rare event.

When I was a kid my friend's house had a bunch of electrical stuff damaged after a high voltage transmission line fell on a lower voltage line and caused the voltage to go way up, probably limited by saturation of the transformer feeding his house. I don't know the exact circumstances around that but it's the only time I've heard of such a thing happening.

[Berni]

Yep fallen off neutral can cause that exessive voltage.

Similar thing happens in 3 phase if the neutral gets disconnected for some reason. The load is never quite ballanced when a bunch of single phase loads are hanging off it, so when neutral falls away that neutral point gets dragged off towards the most loaded phase, causing a lot more voltage to show up on the other two phases. Its perhaps not as bad as on split phase since worst case you can get is 400V, so not quite double the normal voltage, but its still plenty enugh to fry stuff, specialy power supplies.

As for running a VFD around the house they are not really ment to do that since they also have some current feedback and the output waveforms can be quite a PWM mess. But you can certainly buy a huge beefy 3 phase UPS and use it for that.

[Zucca]

something on the bench when I need 50Hz power for something.

Some ghetto gangs use a 50Hz signal generator into an audio amplifier. the speaker output are then connected to some secondaty trafo. Finally the DUT is then feeded by the trafo primary.

[james_s]

something on the bench when I need 50Hz power for something.

Some ghetto gangs use a 50Hz signal generator into an audio amplifier. the speaker output are then connected to some secondaty trafo. Finally the DUT is then feeded by the trafo primary.

I've seen it done. I came into possession of an old California Instruments "Invertron" which is essentially a big linear amplifier driving an output transformer which will deliver 500VA at up to 300V at a frequency from 40Hz to 5kHz. It's a boatanchor and has a very noisy fan but it does the job. I've also got a modern true sine inverter board that I need to finish building into a completed unit at some point.

[JohnG]

Reason I am asking is maybe I will move to US, and I have all my tools/equipment from EU I want to use in USA.
The plan is to rewire the US home taking the 240VAC 60HZ into a 40A European RCD on a separate EU panel and install some german schuko plugs in my future home.
VFD is nice but I think I will not bother to power my EU stuff.

I personally like much more the european 240VAC plugs and grid network components.
Nothing can beat a IEC 60309.. The blue ones, I love them... and I will install somel in my future USA garage for sure.

The US plugs are poorly designed in my eyes.

PS: I lived already in USA and one day the lights were acting funny, I measured the main and I was getting 230VAC in the 110VAC ones. Probably some street trafo went kaboom...
Some little switching PSU melted but thank God nothing big was on during the grip malfunction.
My home will have something if vmain> 140VAC or so then cut the power, thank you and goodbye.

I don't think it's legal to do what you propose, however I don't think anyone is likely to come hassle you about it either. I've thought it would be amusing to install a UK socket in my den/office/project room fed by a 240V 50Hz inverter in the garage but instead I've just set up something on the bench when I need 50Hz power for something.

Definitely not code to rewire in this way throughout the house. Why does it matter? If you ever have a fire or any electrical problem, your insurance companies will not pay you anything, and if someone gets hurt or worse, you will be sued within an inch of your life. Or, if you ever plan to sell your house, the modified wiring system will be a huge liability.

You may be able to have a separate wiring systems as long as it can somehow be considered "not permanent", and have it plug into a 240V outlet in the garage. We do have 240V outlets and wiring that meets code, but they are not European.

Unless you just plan to live in the boonies and you don't care about any of this stuff. Then you can just do whatever you want.

John