US Mains Voltages and Current

[skeeterb]

I'm trying to find information on what the current and voltages that run through the lines between the substation and the house transformers. I know the voltages that come out of the transformers but not the current going into the meter base from the transformer. I am wanting to build windmills that put out the 240V that usually go into a house from the poles. I am also looking for information on how many coils and how many coils per coil would be required for the standard 60 Hz mains frequency. I've been hitting search engines for information but some of the information I have seen doesn't hive the line currents just the frequency and voltages.

 

[RCinFLA]

There is no fixed number of turns for 240v. It depends on the amount of iron in the core and what magnetizing inductance is desired.

You don't need to know anything about pole transformer other then its output current rating. Most can do at least 200 amps but it depends on size of transformer installed. There are small ones for running traffic lights or road signs for example.

 

[KeepItSimpleStupid]

This question is so confusing. A high voltage supplies the primary of the transformer on the order of 7-10 kV. Current can be zero up.
Services depend on when it was installed. Might be 60, 125, 150, 200 or anything in between. 400 A services as 2 x 200 A can also exist. In very RARE instances 3 phase is available for residential in the US.


100-125 A is a typical maximum load breaker.

 

[skeeterb]

I'm trying to find information to build windmills that does not use a battery and inverter to store power but connects directly into the breaker box so it can be utilized in an Off-grid home.I know it may take more than one windmill to create enough power, but i think it CAN be done. I know for a fact that there is a pretty steady wind above the tree lines, because of me climbing a inactive firetower to just under the observation platform and standing looking out over the area. If the towers are raised to a point above the tree line here, we would probably be able to draw enough power to run a house. The reason I'm asking the questions I am, is I'm trying to figure out how many Kilowatts are introduced into the breaker box from the the pole transformer. With that information I can try to figure out how to set up my windmills to produce the power to drive an entire house, off grid.

Edit: another reason I don't want batteries and an Inverter is that even though there are some excellent inverters out there, they will fail at some point. The batteries are also a known point of failure. The best batteries and inverters are WELL out of my reach and I know that if I did invest in them, at some point in time they WILL fail. Plus most batteries have a limited life, no matter which type is used.

 

[RCinFLA]

I'm trying to find information to build windmills that does not use a battery and inverter to store power but connects directly into the breaker box so it can be utilized in an Off-grid home.I know it may take more than one windmill to create enough power, but i think it CAN be done. I know for a fact that there is a pretty steady wind above the tree lines, because of me climbing a inactive firetower to just under the observation platform and standing looking out over the area. If the towers are raised to a point above the tree line here, we would probably be able to draw enough power to run a house. The reason I'm asking the questions I am, is I'm trying to figure out how many Kilowatts are introduced into the breaker box from the the pole transformer. With that information I can try to figure out how to set up my windmills to produce the power to drive an entire house, off grid.

You have a lot of information to learn about to do grid connected interface.

The amount of current that can be introduced into a breaker panel from a renewable energy source is dependent on rating of breaker box and size of incoming main breaker from grid. NEC specs allow for a 120% of breaker box bus rating. If you have a 200 amp breaker box and a 200 amp grid main breaker you can push a maximum of 40 amps (9.6 kW) into breaker box bus from a renewable energy source. If you have a 200 amp breaker bus and reduce the main grid input breaker to 150 amp then you can supply a maximum of 90 amps (21.6 kW) into the breaker bus from renewable energy source.

The principle is the regular branch loads could consume all the grid input current plus the renewal input source and this combined amperage must not exceed 120% of breaker box bus rating.

There are a number of regulations regarding grid tie inverters. The spec is UL1741 which deals with ability of inverter to sense loss of grid and shut down. The main objective here is to avoid 'islanding' where the inverter continues to feed an open grid.

 

[Reloadron]

I'm trying to find information to build windmills that does not use a battery and inverter to store power but connects directly into the breaker box so it can be utilized in an Off-grid home.I know it may take more than one windmill to create enough power, but i think it CAN be done. I know for a fact that there is a pretty steady wind above the tree lines, because of me climbing a inactive firetower to just under the observation platform and standing looking out over the area. If the towers are raised to a point above the tree line here, we would probably be able to draw enough power to run a house. The reason I'm asking the questions I am, is I'm trying to figure out how many Kilowatts are introduced into the breaker box from the the pole transformer. With that information I can try to figure out how to set up my windmills to produce the power to drive an entire house, off grid.

Edit: another reason I don't want batteries and an Inverter is that even though there are some excellent inverters out there, they will fail at some point. The batteries are also a known point of failure. The best batteries and inverters are WELL out of my reach and I know that if I did invest in them, at some point in time they WILL fail. Plus most batteries have a limited life, no matter which type is used.

OK, just for the heck of it let's drop the grid, let's assume there is no grid. Typical US mains power (residential) consist of 240 VAC 60 Hz in a split phase configuration. The first big problem is the 60 Hz. That 60 Hz frequency will be a direct function of the rotational speed of the wind turbine alternator generating it. That means the alternator must rotate at a constant speed. Therefore preceding the alternator you need a CSD (Constant Speed Drive) mechanical linkage between the blades and the actual alternator. That alone is a major expensive obstacle to overcome. This is why many large wind turbines are DC generators that in turn feed an inverter. This is but one reason why the inverter is an integral part of the system.

If you want to screw around with this I suggest you find yourself an automotive alternator and hack it. A common automotive unit is actually a 3 phase AC alternator before the rectification takes place and regulation to get > 12 VDC.

Ron

 

[Birdman Adam]

What I would suggest is you go the inverter route. There are many options that automatically lock in with the mains frequency, and turn off the output when mains power goes away (so you dont try to backfeed and possibly shock the lineman fixing the problem). Then all you need to do is feed the invert DC current between a particular voltage range (say 12-48VDC). So when building your windmill, use DC generators!

 

[skeeterb]

The type of generator that I was planning on building is an axial flux permanent magnet generator, configured in the 3 Phase star configuration.

 

[Reloadron]

The type of generator that I was planning on building is an axial flux permanent magnet generator, configured in the 3 Phase star configuration.

How do you plan to control the frequency and voltage but specifically the frequency?

Ron

 

[Mr RB]

On most grid connect windmills they use fixed gearing and vaiable pitch blades on the turbine. The blade pitch is varied to get the RPM to sync point then they are grid connected and the pitch reduced to start feeding power into the synchronous generator.

That is going to be hard with no grid to connect to! Even if you try to control RPM constantly to keep freq correct you won't be able to control the power output...

 

[Reloadron]

This is a little off topic but mildly interesting stuff. I recently (over the past few months) watched the construction of what I guess is one of the largest wind turbines on the North American Continent. It went in behind where I work so when I took breaks I would go out and watch the progress. The unit was installed at Lincoln Electric in Cleveland, Ohio USA.

Turbine by the numbers

800,000: Approximate total weight in pounds, including the turbine and & tower
279: Turbine hub height in feet
444: Height of top blade tip in feet
165: Length of each blade in feet
2.5: Maximum output of electricity in megawatts (2,500,000 watts) at 690 volts direct current, converted to 4,160 volts AC on the ground for use in Lincoln's shops.

The thing is a monster, everything around it that was big is now dwarfed in its shadow. The blades are actually fixed pitch and the thing has a hell of a gearbox at the hub. Rotational speed at the blades is only about 15 RPM when generating full power of 2.5 MW. Think about 2.5 MW at 690 VDC? The down bus has to be huge! This thing was shipped from Germany.

This is one of several articles about it that ran locally and includes a picture of it during build. A Google of Lincoln Electric Wind Turbine will bring up other articles and images of the beast.

Interesting as I mentioned was the use of fixed pitch and not variable blades. However, it is a DC generator sitting up there. The inverters also must be huge to run the 4160 VAC @ 2.5 MW.

Ron

 

[RCinFLA]

The only ones that use syncronous alternator are large commercial windmills. They are maintainence intensive and require a relatively constant wind velocity. They don't work well in gusty or variable wind direction areas.

Smaller residential units use permanent magnet three phase alternator (PMA) with full wave rectifiers, similar to automotive alternator except with permanent magnet rare earth magnet rotors. A DC to AC grid tie inverter is used to back feed grid. You need a steering tail, breaking system, or load dump system to prevent run away in high winds or when grid goes down. The system is very close to an inverter-generator like Honda's or Yamaha's with exception of wind turbine in place of gasoline engine.

 

[tytower]

I thought America had 110 Volt power to houses ?
Australia has 240 Volt as do many others but has the States moved that way too ?

 

[Reloadron]

I thought America had 110 Volt power to houses ?
Australia has 240 Volt as do many others but has the States moved that way too ?

US Residential mains power comes in as 240 VAC 60 Hz. split phase. It is distributed in the residence as 120 VAC 60 Hz. However, there is also 240 volts for large appliances like air conditioning, electric stoves, clothes driers and such. 110 vac was many years ago when the entry was 220 volts ac split phase.

Ron

 

[Mr RB]

...

Interesting as I mentioned was the use of fixed pitch and not variable blades. However, it is a DC generator sitting up there. The inverters also must be huge to run the 4160 VAC @ 2.5 MW.
...

Looks like the dumb journalists got their "wires crossed".

That company Kenersys that made your windmill only make "Synerdrive" windmills, 3 different products and all are synchronous AC with variable pitch blades.

See their web page here;
**broken link removed**

Here's a quote from that page;

CUTTING EDGE SYNERDRIVE TECHNOLOGY

KENERSYS concentrates on multi-megawatt on-shore turbines. The three platforms K110 2.4MW, K100 2.5MW and K82 2.0MW are pitch regulated, variable speed, full conversion turbines with a synchronous generator. They are designed to suit wind regimes according to IEC Type Class IIa and IIIa respectively.

Your 2.5MW turbine is their middle sized model.

 

[Reloadron]

Hi Mr. RB, I'll have to check more into it. A guy who did part of the balancing told me fixed and I never saw mention of variable pitch. What I do know is that sucker is huge, dwarfing everything around it. Thanks for the additional info.

Ron

 

[Mr RB]

Yeah I'm interested in why they would say that. It could still be right and they may be fixed pitch, although I assume the "pitch regulated" claim on their web site means variable pitch.

Another giveaway is looking at the photo where the 3 blades enter the hub, they are on circular rings (typical of variable pitch blade turbines);

**broken link removed**

And of course the benefits of variable pitch are so huge that (as far as I know) all the really big commercial style windmills use it.

 

[Reloadron]

I had a good angle today and sure as hell, it is variable pitch. I think many of the guys who work on it really don't have a handle on much more than their specialty. The circular rings look very pronounced. While from my vantage point I have yet to notice a pitch change the thing keeps busy. Nothing on ground level but a gentle breeze but it keeps turning way up there. I found the max rotational speed of 14 RPM to be impressive. When we start getting good November winds I'll have to check it out.

Thanks Again Mr RB for the wealth of information.
Ron

 

[jpanhalt]

<snip> What I do know is that sucker is huge, dwarfing everything around it.
Ron

That is huge and the blade arc is considerably larger than a 747-400's wingspan, which is only about 212 ft. Now, I have a reason to visit East Cleveland.

John

 

[Reloadron]

That is huge and the blade arc is considerably larger than a 747-400's wingspan, which is only about 212 ft. Now, I have a reason to visit East Cleveland.

John

Yeah John, you are local, you should check out this beast. Actually in Euclid.

Ron