TESLA VS. EDISON

[weressl]

Yep, sorry. The bitter irony is Amtrak lacks the money to replace the system & thus just spent million$ rebuilding 60Hz->25 Hz converters. Seems the solid state ones have a pretty nasty harmonic output level which the rotary ones eat.

The NYC-Boston region is all 25KV/60 Hz as is the rolling stock; but not points south.

Oh, and I am sure that the 'rebuilding' had fattened certain targeted local individuals pockets, whereas the SS convereters would come from out of State as they have driven manufacturing out from the State by taxation.

 

[ggunn]

Thank you kindly.

That would be TYK. Get with the program, willya? ;^)

 

[Besoeker]

Within a section, my understanding is yes.

I still don't see how an inductive machine would sink harmonics.
The reason PWM inverters produce fairly good sinusoidal currents is because and reject the high frequency content of the PWM waveform.

 

[Open Neutral]

It's been too long since Machines for me to expound with confidence...

But ordinary delta transformers help eat harmonics; wouldn't a delta transformer with a moving armature do the same?

[BTW, it looks like over a ~~100 mile segment, there are ~10 of their 138KV->12KV substations, all fed further overhead HV.]

 

[Besoeker]

It's been too long since Machines for me to expound with confidence...

But ordinary delta transformers help eat harmonics; wouldn't a delta transformer with a moving armature do the same?

[BTW, it looks like over a ~~100 mile segment, there are ~10 of their 138KV->12KV substations, all fed further overhead HV.]

As far as I recall, a delta winding will circulate third harmonic. For a solid state converter I'd be surprised if it produced such low order harmonics.

 

[Open Neutral]

My mention of delta was wrong for a bigger reason. PRR/NE Corridor is 1∅ not 3.

So I fully admit I don't know how the rotary converters help on the harmonics problem; only that I read somewhere RR-ish that because of harmonics from the static ones at Jerico Park; they were rebuilding some of the rotary ones. But the links I chased on such were all dead & not in the Internet Archive.

 

[Fulthrotl]

There is a lot to this discussion and I don't have time to type up the 1000 word essay required to answer it, but the big difference is today we have the ability to "transform" DC to higher transmission voltages and down to usable voltages at the loads, 100 years ago we did not. DC has less losses and a DC transmossion system would be much better than what we have now, but that means starting all over.

yeah, hvdc transmission for huge amounts of power point to point is done, and works well,
but it's still the exception rather than the rule... it'll change over time, but there is 100
years of infrastructure that doesn't support it.

as for tesla, there's a good chance he understood resonant frequency better than almost
anyone before, or since. from dc, to white light, everything has a frequency, including DNA.

first, and only tesla coil i every made i was 20 years old, and it was a water bath capacitor
rig using beer bottles for dielectric... that worked poorly, as most 6 beer hot flashes seem
to do, so i "tested" at home some pretty healthy dielectric caps that we were making at the
time for the US military for use on submarines.... across 220 volts, it was a thing to behold.

don't try this at home. when it was tuned, it was awesome. when it wasn't, it tripped the
30 amp circuit it was on.... i didn't fully understand that you could have composite output
including a harmonic of the primary voltage, which sorta is lethal. fortunately, i only had
the "lightning from the fingertips" experimental stuff when it was in tune..... so it didn't kill me.

but tesla's genius is unquestionable. before the turn of the last century, he'd mathematically
derived the frequency of the sand underneath new york, if memory serves, and was putting
mechanical energy into the ground at a specific frequency, to create a standing wave in the
sand, and form a storage cell for mechanical energy in the earth... then there was the
earthquake, and that experimental series was shelved....

of the three key players, tesla, westinghouse, and edison, my perception is that
edison wasn't so much brilliant as stubbornly persistant, and pretty ruthless in
stifling competition.

westinghouse was a shrewd buisnessman, and made a lot more money after he
defaulted in his licensing agreement with tesla, and reneged on the royalties he
was supposed to pay.

and tesla was the genius that couldn't accomplish anything without some backing.
and he had poor abilities in picking partners.

 

[Cmdr_Suds]

Going the other direction, the aviation industry uses 400Hz in commercial aircraft. I believe this is to allow for smaller transformers and reduced weight. Modern terminals have 60Hz to 400Hz power units at the gates so they can keep the plane powered up when the engines are sutdown.

 

[S'mise]

Not even close

Not even close

Edison was brilliant because of his tenacity but he was a welsher and a dirtbag. He actually "westinghoused" Topsy the elephant to show how dangerous that newfangled AC was.(Just to discredit Tesla) surely not something to have in your house.:lol:

Tesla deserves 97% of the credit for modern electrical systems and radio. Edison became famous for "inventing" the light bulb which he did not invent, merely improve on it. I think the gramaphone was a great invention but the polyphase brushles motor blows it away.

Probably every appliance or electronic device in your house exists because of Tesla.

Ps: Marconi stole some of Tesla's thunder too.

 

[jimbo123]

CONTROL FREQ good topic did not know much about telsa until tonight. Heard his name once or twice before, thats it.
The reason for my post is you brought up about some of the guys that always seem to come up with most of the answers to our questions and i totatly agree with you. I've have come to depand on these guys for my questions that at the time seem impossible for me to figure out, yet they just make it look so easy. Seems like a good time to say thank you all for the help you all have given.
Agree they are very smart.

 

[Strife]

4 reasons come quickly in mind. I'm sure there are plenty others, but I think these four stand up.
1: Generating the electricity.
2: Transmission.
3: Motors tend to be cheaper in AC than DC. AC motors are virtually maintenance free. Imagine having to change brushes in a compressor motor.
4: Having 3 phases. Imagine a 100HP motor with just positive and negative instead of 3 wires. Yes that 1/3 additional wire reduces the amperage by 1.74.
Mainly everything to do with using a magnetic field would be affected. The DC creates a uni directional magnetic field, whereas the AC cause the magnetic field to fluctuate. I might be wrong, but I never heard of a DC transformer (just plain DC transformer, NOT an inverter, transformer, etc system)

Between Mike Holt?s newsletter about knowledge and history, and Bob Johnson?s recent ?conundrum? I?ve decided to ask you guys about a few things. DISCLAIMER: I?ll say it up front, there aren?t many people I know personally that share my passionate interest in this subject, so I truly hope this is the proper place for this discussion. ALSO, I could never afford to attend any college (unless you count 8 years of 12B Combat Engineer training, which most people don?t) so forgive me if? no, WHEN--I am completely in the dark about things. That said, here we go:


WHY IS IT AGAIN, THAT OUR HOMES ARE POWERED WITH AC, INSTEAD OF DC???

 

[Besoeker]

4 reasons come quickly in mind. I'm sure there are plenty others, but I think these four stand up.

1: Generating the electricity.

Yes, usually alternators for bulk power generation. There are cases where it isn't. Solar PV, for example, is DC.

2: Transmission.

For transmission HVDC is also used, particularly but not exclusively, for long distances. The cross channel HVDC link (France to UK) is about 40 miles long.

3: Motors tend to be cheaper in AC than DC. AC motors are virtually maintenance free. Imagine having to change brushes in a compressor motor.

Why particularly in a compressor motor?

4: Having 3 phases. Imagine a 100HP motor with just positive and negative instead of 3 wires. Yes that 1/3 additional wire reduces the amperage by 1.74.

That's simply not true. Here's actual data from a 100kW DC motor - the nearest rating to your 100hp that I have on file. Armature voltage is 600Vdc and current is 183A. It's a variable speed machine and the DC system that it runs from comes from rectified 525Vac. For a 525V 100kW cage induction motor running from the same supply the current would be in the region of 140A. The ratio isn't 1.74.

 

[Strife]

Yes, usually alternators for bulk power generation. There are cases where it isn't. Solar PV, for example, is DC.

PV Is extremely new. Kinda hard to implement what the OP was asking with something that's still not the major power generation. Not to mention, I don't see PV lasting too long..

For transmission HVDC is also used, particularly but not exclusively, for long distances. The cross channel HVDC link (France to UK) is about 40 miles long.

Same as above, more or less. Bottom line, if transmission would be cheaper and more feasible in DC it'd be more widespread.

Why particularly in a compressor motor?

Was referring to AC compressors. They tend to be encapsulated. Kinda difficult to service it when you have to cut the shell to do so.

That's simply not true. Here's actual data from a 100kW DC motor - the nearest rating to your 100hp that I have on file. Armature voltage is 600Vdc and current is 183A. It's a variable speed machine and the DC system that it runs from comes from rectified 525Vac. For a 525V 100kW cage induction motor running from the same supply the current would be in the region of 140A. The ratio isn't 1.74.

In Europe the rating is in KW, which is what it CONSUMES.
In US motors are rated in HP, which is what they can PUT OUT. As a HP is (around) 760W and most motors have an efficiency of 0.6-0.7 most times the HP is kinda the KW it'll use. For a quick calculation of FLA I always use 1HP for 1KW, but most motors tend to use a little more than that.
But even at that, assuming a 525V 3 phase system the FLA would be 109A, multiplied by 1.74 = 189A (pretty close to your 183A).
At the 480V system, 3phase a 100HP motor (which again is a little more than 100KW) is 128A. Even at that, there's a big difference between a #1 wire and a #2/0.
And is not only motors, any load works same way. ANY 100KVA load at 510 DC(adjusting the fact that DC is slightly higher than a 480VAC) is almost 200A. The same load at 480V AC 3 Phase would be 120A. 120 times 1.74 equals 208. pretty close. So again I can have a service with #2 wire VS a #3/0 wire by just adding 1/3rd more wire. Price wise the #2 is almost 3 times cheaper. Not to mention conduit sizes and such. Basically 2000 feet of #3/0 is over 6K. 3000 feet of #2 is about 3800.

 

[Besoeker]

PV Is extremely new. Kinda hard to implement what the OP was asking with something that's still not the major power generation. Not to mention, I don't see PV lasting too long..

Why do you think that?

Same as above, more or less. Bottom line, if transmission would be cheaper and more feasible in DC it'd be more widespread.

It might be more widespread that you think. There are around 140 systems world wide and some currently under construction. If, in those cases,it wasn't cheaper and more feasible, it wouldn't be being done.

Was referring to AC compressors. They tend to be encapsulated. Kinda difficult to service it when you have to cut the shell to do so.

Point taken. Not something I deal with. For me, a compressor is usually in the few hundred to few thousand kW range...

In Europe the rating is in KW, which is what it CONSUMES.

Not so. The kW rating on the nameplate is the output power in kW. The input power is, of course, higher than the input power by the losses.

In US motors are rated in HP, which is what they can PUT OUT. As a HP is (around) 760W and most motors have an efficiency of 0.6-0.7 most times the HP is kinda the KW it'll use. For a quick calculation of FLA I always use 1HP for 1KW, but most motors tend to use a little more than that.

The DC motor I gave you nameplate details for is rated at 100kW output. With 600V and 183A, its input power is a little under 110kW. That gives the motor and efficiency of 91%, not the 60% to 70% you are suggesting for most motors. In fact, I can't ever remember coming across a motor of much under about 90%. We make some brushless DC motors that are better than 97% and many of the cage induction motors are of that order. On many of the projects we undertake, we have to provide guaranteed efficiencies for drive systems including motor losses.
This is typical:

But even at that, assuming a 525V 3 phase system the FLA would be 109A

That's 100kVA, not 100kW. You forgot about power factor and efficiency

At the 480V system, 3phase a 100HP motor (which again is a little more than 100KW) is 128A.

100HP is about 75kW

on wire sizes

US wire sizes I'd have to do a conversion on. I can, but I'm to indolent to do so for this. But don't forget that a DC machine has two main conductors as opposed to three for an AC machine.[/quote]

And is not only motors, any load works same way. ANY 100KVA load at 510 DC (adjusting the fact that DC is slightly higher than a 480VAC) is almost 200A. The same load at 480V AC 3 Phase would be 120A. 120 times 1.74 equals 208. pretty close.

Why pick 510Vdc? A rectified 480Vac 3-phase supply would result in about 650Vdc. A 200A current drawn from that would be close to 130kW. Note 130kW, not kVA.
A current of 120A at 480V 3-phase gets you about 100kVA. The most you can get is 100kW at unity power factor. To get that from the 650Vdc would be 154A. Simple arithmetic then gives you a ratio of 1.18:1.
But what if the AC load has a power factor of say, 0.8? Not uncommon for an induction motor. That would give you 80kW. The current from both DC and AC systems would be about the same. And the DC system would need just two main conductors.

 

[CONTROL FREQ]

BESOEKER, that post was awesome. I have barely had time to check in lately, but these posts are incredibly informative... I wonder sometimes where is the "TESLA" of OUR generation? We seem to be surrounded by "EDISONS". BUT having said that---the mere fact that we are exploring this question is kind of ahead of our time (in my opinion). I'm personally becoming increasingly convinced that in the future, we'll buy our solar panels and windmills from china, because fossil fueled power generation will be 'illegal'... and the only jobs for "us" will be in service industries. But who will we serve? ourselves? our masters? who? CLEAN/GREEN is here to stay, no matter what anyone does or says, the "bottom line" is what counts, and right now it is being presented to us that solar and wind are "free" and with the "carbon tax" already WELL on its way to reality, it's just a matter of time until fossil fuels are either illegal, or 'too expensive' (tax or otherwise) for anyone to use. Then what? when the dollar/euro are worthless, what will we ever trade to get these valuable PV panels or windmills? maybe our drilling rights? Maybe our mining/mineral rights? Then I would imagine china might pay off enough of our government to ease up on the carbon tax, or legalize fossil fuels again... purely ridiculous speculation that might run through one's head when he's bored of running pipe and pulling wire day in... and day out... wouldn't it be a real kick in the crotch if someday we who love this place so much, had to watch our grandchildren pay the chinese to pollute all this, so they could have power for their homes (and also to run the new sweatshops in their backyard). I personally think it would be wise to devolop the most efficient equipment possible, so we can use only what we need, while staying "on top" globally, if wecan't do that, then we need to just produce strictly for ourselves. That would be kinda like the PV cells and windmills... YOU DON'T NEED THE POWER COMPANIES IF YOU CAN DO IT YOURSELF!!! and we don't need china, india, korea, japan, or anyone else, if we could just get back to self-reliance. Apologize if ranting, guess I should go to bed...

 

[Besoeker]

BESOEKER, that post was awesome.

Hi CF.
Thank you for your kind words.
I’ve been in the electrical business for quite a few decades - some of it is bound to stick….

I'm personally becoming increasingly convinced that in the future, we'll buy our solar panels and windmills from china, because fossil fueled power generation will be 'illegal'... and the only jobs for "us" will be in service industries. But who will we serve? ourselves? our masters? who? CLEAN/GREEN is here to stay, no matter what anyone does or says

I agree that clean/green is a good thing. That said, I think we have some major hurdles to overcome before it becomes mainstream and supplant fossils. However, setting aside all the arguments about costs and NIMBYism, there is a major technical point that needs to be resolved.

We have on demand expectations but the clean/green renewables are on availability sources*. On a calm, dark night neither PV nor wind will meet that on demand expectation. At present, the slack is taken up by having spinning reserve, conventional fossil driven generators running lightly loaded until required to supplement the renewable sources. The problem with this is that running lightly loaded is inefficient so the emissions increase in relation to the energy generated. There is a point at which the reduction in emissions resulting from the use of renewables is offset by the increased emissions from the lightly loaded conventional generation. I’ve seen various figures for this but often 20% from variable sources is about as much as can be accommodated on a grid.

One way round this would be storage at large scale storage is being developed. We don’t yet have that. At domestic level, you could live off-grid and some do. Location and lifestyle significantly factor into this. The best places for PV are sunny like deserts. For wind, mountains or offshore. Not so many people do. If you lived in London or New York, off-grid is probably not a practical proposition.

I personally think it would be wise to devolop the most efficient equipment possible,

I think we’re getting there. Our television uses less than 1W on standby for example.

*Hydro is an exception. The differentiator is that it has storage. All that water behind the dam is stored potential energy.

 

[weressl]

BESOEKER, that post was awesome. I have barely had time to check in lately, but these posts are incredibly informative... I wonder sometimes where is the "TESLA" of OUR generation? We seem to be surrounded by "EDISONS". BUT having said that---the mere fact that we are exploring this question is kind of ahead of our time (in my opinion). I'm personally becoming increasingly convinced that in the future, we'll buy our solar panels and windmills from china, because fossil fueled power generation will be 'illegal'... and the only jobs for "us" will be in service industries. But who will we serve? ourselves? our masters? who? CLEAN/GREEN is here to stay, no matter what anyone does or says, the "bottom line" is what counts, and right now it is being presented to us that solar and wind are "free" and with the "carbon tax" already WELL on its way to reality, it's just a matter of time until fossil fuels are either illegal, or 'too expensive' (tax or otherwise) for anyone to use. Then what? when the dollar/euro are worthless, what will we ever trade to get these valuable PV panels or windmills? maybe our drilling rights? Maybe our mining/mineral rights? Then I would imagine china might pay off enough of our government to ease up on the carbon tax, or legalize fossil fuels again... purely ridiculous speculation that might run through one's head when he's bored of running pipe and pulling wire day in... and day out... wouldn't it be a real kick in the crotch if someday we who love this place so much, had to watch our grandchildren pay the chinese to pollute all this, so they could have power for their homes (and also to run the new sweatshops in their backyard). I personally think it would be wise to devolop the most efficient equipment possible, so we can use only what we need, while staying "on top" globally, if wecan't do that, then we need to just produce strictly for ourselves. That would be kinda like the PV cells and windmills... YOU DON'T NEED THE POWER COMPANIES IF YOU CAN DO IT YOURSELF!!! and we don't need china, india, korea, japan, or anyone else, if we could just get back to self-reliance. Apologize if ranting, guess I should go to bed...

Perhaps the problem lies with you who is "running pipe and pulling wire day in... and day out..." and not preoccupied with formulating policies or Governmental Regulations or trying to place one more angel on the top of a pinhead. You just retained to much common sense that blocks you from being 'progressive". Get with the program, will ya?!:lol:

 

[jpage]

Why invert, why transmit, why not just generate, store and consume when needed?:slaphead:

You have to remember that the playing field in the 19th century did not have semiconductor devices. Both AC and DC need to be transformed to higher voltages for transmission. The transformer made that practical, efficient and inexpensive for AC systems. The DC systems of the time could only transform voltage through a motor-gen set, which was bigger, more expensive, less efficient and required more maintenance than a transformer. The rectifier would come around some 50 years later and make DC to DC conversion more practical, but by that point, we were committed to AC.

The reason for using DC transmission lines is that the price and losses are comparable to AC, without the need to synchronize the phases (that is done during inversion).