Enphase Mico Inverter

[Naptown]

I can't say the were degree'd or not but you just don't want to challenge someone in the commissioning process, but one said he was an electrician in the Navy with nuke background and he had gray hair not a "freshman" the other was in his forties, and a little pudgy not with lineman background. For what ever reason they were discussing DC from roof panels and the fact that firemen were concerned for what ever reason. This was a discussion they were mumbling about. I also heard them say something about marking DC conduit every 10' may be a requirement etc. Not sure why but? They may not be designer of HVDC, but you never know what their background may have been, so don't assume anything.

Myself I started out in the Navy rewinding 3 phase motors, our ship was 440V 3 phase. I worked in the electronic industry for 32 years, 25 in the CTR industry, and 7 in the display monitor industry. I started out as a tech and ended up as a Director of engineering both in manufacturing and design. I got my degrees while going to night school. I worked in process engineering most of my time, and we helped straighten out a lot of bad designs. In the 31 years I knew a lot of none degree'd engineers who could do more and perform better than seasoned engineers. So don't sell them short, everything you see on here or discussed on here is not absolute or absolutely correct.

They were mumbling about NEC requirements not necessarily engineering. I routinely have to mark conduit carrying conductors with DC current every 10'

[bwillng]

I agree - but the "engineers" they send out to commission solar power systems are typically not the people designing HVDC power transmission systems.

I can't say the were degree'd or not but you just don't want to challenge someone in the commissioning process, but one said he was an electrician in the Navy with nuke background and he had gray hair not a "freshman" the other was in his forties, and a little pudgy not with lineman background. For what ever reason they were discussing DC from roof panels and the fact that firemen were concerned for what ever reason. This was a discussion they were mumbling about. I also heard them say something about marking DC conduit every 10' may be a requirement etc. Not sure why but? They may not be designer of HVDC, but you never know what their background may have been, so don't assume anything.

Myself I started out in the Navy rewinding 3 phase motors, our ship was 440V 3 phase. I worked in the electronic industry for 32 years, 25 in the CTR industry, and 7 in the display monitor industry. I started out as a tech and ended up as a Director of engineering both in manufacturing and design. I got my degrees while going to night school. I worked in process engineering most of my time, and we helped straighten out a lot of bad designs. In the 31 years I knew a lot of none degree'd engineers who could do more and perform better than seasoned engineers. So don't sell them short, everything you see on here or discussed on here is not absolute or absolutely correct.

[billvon]

I seriously doubt that. Just about every large Power company uses HVDC transmission from the plant to distribution in most cases.

I agree - but the "engineers" they send out to commission solar power systems are typically not the people designing HVDC power transmission systems.

[Sunking]

"Power company engineers" often know only what the power company teaches. Not a bad thing, since that's all they deal with; they've likely never seen a DC power system.

I seriously doubt that. Just about every large Power company uses HVDC transmission from the plant to distribution in most cases. I designed and built them 30 years ago between POCO in TX-OK-LA-NM. They are quite common. Not too mention all the sub stations use 140 VDC switching to control everything. Every wind farm in the USA is HVDC transmission to the point of distribution. So I would say POCO Engineers are experts on DC power.

[russ]

I brought up this topic with the two engineers from the power company while the were commissioning my solar system and they do not agree with you and they said my facts were correct. Again I ask "now many of you actually receive DC from your power company?" I don't think many of your appliance would work on DC at least those that had transformers maybe a universal motor! I know shaded pole motors and induction motors rely on the cyclical field in AC. That means drill presses, saws, lathes, etc rely on AC.

Two power company engineers commissioning a solar system? Engineers with a degree and experience or technicians - there can be a rather large difference in knowledge and understanding. An engineer directly out of the university is often capable of little more than holding a door open - with experience their capability normally improves - though not always.

[russ]

In general industry you used to see some DC drives until the frequency control units were fully developed - now you see virtually none - special applications aside.

[billvon]

I brought up this topic with the two engineers from the power company while the were commissioning my solar system and they do not agree with you and they said my facts were correct.

"Power company engineers" often know only what the power company teaches. Not a bad thing, since that's all they deal with; they've likely never seen a DC power system.

I don't think many of your appliance would work on DC

The following will all work on DC power:

Anything with a switchmode supply (computers, chargers, laptops, anything with a modern wall wart, LCD TV's)
Any resistance heater
Any universal motor (hair dryers, fans etc.)
Incandescent lamps, switchmode CFL's, electronically ballasted fluorescent lamps and LED lamps

As time goes on, the one component that will NOT work on DC power (transformers) are being phased out in favor of AC/DC switchmode converters for reasons of size, cost and efficiency. That's one reason that new buildings use DC distribution instead of AC.

That means drill presses, saws, lathes, etc rely on AC.

Many small drills, saws etc use universal motors. And most cordless devices use switchmode chargers for their batteries and will work just fine. In our house roughly 80% of our load will run on DC.

[Naptown]

Well yes and no Rich. Depends on what the application is. If you need a lot of torque like those required in a traction motor for trains, or precision speed placement control DC motors are the way to go. DC motors are also much less expensive and less complicated to control speed. However DC motors have a few significant disadvantages like inefficient, short service life, and as RPM increases torque decreases.

these advantages are what I was referring to.
Almost infinitely variable speed and torque

[Sunking]

When it comes to Motors DC rules.

Well yes and no Rich. Depends on what the application is. If you need a lot of torque like those required in a traction motor for trains, or precision speed placement control DC motors are the way to go. DC motors are also much less expensive and less complicated to control speed. However DC motors have a few significant disadvantages like inefficient, short service life, and as RPM increases torque decreases.

AC motors on the other hand most are extremely efficient on the order of +90%. precision speed control, and best of all many provide constant torque all through the power band. A fact that has not escaped the Electric Vehicle industry. Even most golf cart manufactures are switching to AC motors from traditional DC series and shunt wound motors.

[Sunking]

The TV reference is that Europe waited to adopt a standard and their standard was 600 lines vertical resolution Vs 500 in the US

OK but what does that have to do with 50 or 60 Hz. Maybe I am missing your point?

[Naptown]

Huh? What does AC at 60 Hz have to do with TV resolution? I must be missing something.


That is correct but most motors will operate at either 50 or 60 Hz, they just run a little slower on 50 Hz. However about anything else works just fine at 50 or 60 Hz.

From a transport POV whether it be 50 or 60 Hz is a moot point. Your country or grid area just has to standardize on one or the other. The main disadvantage of going to lower frequencies is the physical size, weight, and amount of material use in transformers and converters. The lower in frequency you go, the larger thew transformers must be. This is why Planes, Ships, Space Craft, and older data centers use 400 Hz. As an example a 1 Kva transformer for 50/60 Hz physical dimensions are about 7 x 10 x 6 and weighs in around 10 pounds. Where as a 1 Kva 400 Hz transformer is about 1 x 1 x1 and only weighs a few ounces.

And Hotter on 50HZ if designed for 60 Resistance loads make no differrence

The TV reference is that Europe waited to adopt a standard and their standard was 600 lines vertical resolution Vs 500 in the US

[Naptown]

Today no one in the USA, however just about all of NYC Manhattan Island was DC up until November 14, 2007. It was phased out over a period of 10 years. Many of the large users have rectifiers to change the AC back to DC to operate large loads like elevators and air conditioning.

Edison built the first electric grid in NYS and it was completely DC up until the mid 90's when they started phasing it out. It was one of Edison's great blunders as Westinghouse rules the electrical world. Tesla invented AC generation and distribution techniques we still use today worldwide, but he was a very poor business mind and never patented his inventions. When he developed AC generation and distribution he worked for Westinghouse who gladly took his inventions and patented them all. Tesla died a poor penny-less man.

To this day all electrical generation is AC and will be for life as it is much easier and cheaper to control with simple transformers and less dangerous than DC.

With that said today POCO's do use HVDC transmission. It is very expensive to implement, but the savings in transmission losses quickly pay off. In TX all power that enters and leaves the state is all DC. TX will not allow any AC transmission line to cross state lines. It is asking for trouble in the form of Black Outs like has been experienced in the North East. It was the Black Out in the North East of 1965 that convinced TX to get off the national grid. One of the smartest things ever done by government.

When it comes to Motors DC rules.

[Sunking]

In the US no one. That's because Edison won over Tesla. This is the same reason we had low definition TV forever. The Europeans who adopted the technology later got higher resolution from waiting.

Huh? What does AC at 60 Hz have to do with TV resolution? I must be missing something.

Same thing with AC power 50 HZ is more efficient than 60 for motors etc.

That is correct but most motors will operate at either 50 or 60 Hz, they just run a little slower on 50 Hz. However about anything else works just fine at 50 or 60 Hz.

From a transport POV whether it be 50 or 60 Hz is a moot point. Your country or grid area just has to standardize on one or the other. The main disadvantage of going to lower frequencies is the physical size, weight, and amount of material use in transformers and converters. The lower in frequency you go, the larger thew transformers must be. This is why Planes, Ships, Space Craft, and older data centers use 400 Hz. As an example a 1 Kva transformer for 50/60 Hz physical dimensions are about 7 x 10 x 6 and weighs in around 10 pounds. Where as a 1 Kva 400 Hz transformer is about 1 x 1 x1 and only weighs a few ounces.

[Sunking]

Again I ask "now many of you actually receive DC from your power company?"

Today no one in the USA, however just about all of NYC Manhattan Island was DC up until November 14, 2007. It was phased out over a period of 10 years. Many of the large users have rectifiers to change the AC back to DC to operate large loads like elevators and air conditioning.

Edison built the first electric grid in NYS and it was completely DC up until the mid 90's when they started phasing it out. It was one of Edison's great blunders as Westinghouse rules the electrical world. Tesla invented AC generation and distribution techniques we still use today worldwide, but he was a very poor business mind and never patented his inventions. When he developed AC generation and distribution he worked for Westinghouse who gladly took his inventions and patented them all. Tesla died a poor penny-less man.

To this day all electrical generation is AC and will be for life as it is much easier and cheaper to control with simple transformers and less dangerous than DC.

With that said today POCO's do use HVDC transmission. It is very expensive to implement, but the savings in transmission losses quickly pay off. In TX all power that enters and leaves the state is all DC. TX will not allow any AC transmission line to cross state lines. It is asking for trouble in the form of Black Outs like has been experienced in the North East. It was the Black Out in the North East of 1965 that convinced TX to get off the national grid. One of the smartest things ever done by government.

[bwillng]

What your wind generator is actually doing is producing AC power of variable frequency. This is rectified to DC then inverted back to AC.

What ever! The bottom line is it delivers AC to my breaker panel. The literature says Up to 400 kWh/month potential output. Mine has created 677kW in almost 3 years on a 60 feet pole. That is why I have gone to solar. After visiting three different solar sites I realized what a big blunder I had made. Back when I first looked at solar the person who came out quoted my $100,00.00 for a system, that jaded my thinking toward wind. By he way the government of Michigan was thinking of only allowing 20 meter poles or 66'. I was on the township planning commission and this was discussed at a state sponsored seminar.