Electricity and Common Urban Myths

[Mosey]

Thanks for correcting my assumption. I vaguely remember that discussion in Pipes & Tubes class back when. Must have been Spring and I was looking out the window.

 

[Don1966]

Pat did you know that the Niagara Falls project of 1895 was Tesla's motors and generators and his project. He and George Westinghouse had a partnership. Westinghouse supplied the funds. When he and George split Tesla let Westighouse have all the assets instead of litigation in court. He want his inventions to live on instead of money, court would of distroyed all his work. This project was the first of its kind and lit New York. Edison made all attempts to make Tesla's AC generates and motors look bad, by going so far as electrocuting an Elephant to show how dangerous it was. He want to profit from it and pushed DC.

Regards don

 

[Dan Rowe]

Don,
Yes the War of Currents was ugly. I have seen the film of the poor elephant who had killed several men but that does not justify not using a high power rifle to humanely kill the beast.

Wiki did not sanitize the facts of the fight between Tesla and Edison.
http://en.wikipedia.org/wiki/War_of_Currents

Dan

 

[Don1966]

Dan the DC motors will soon be a motor of the pass. With the PWM Vector Drive AC motors far surpass that of DC motors. You can burn a motor with over Torque with these drives. This drive has a motor model Algrorithms that calculates the motors Stator and rotor resistance per degree of rotation, and adjust the magnetizing flux and torque flux accordingly. Of coarse it monitors the current and voltage as well. Below is some photos of some of my Toys at work I like to call them.

This is a 1000v 3500amp drive the motor it drives is 3500KW 620volt

don

 

[Noitoen]

Ok, you win. All I have is a Tyssen/Henchel shredder with a 850 Kw. 6Kv motor with direct start. Only thing between the motor and the 17 metric ton rotor is a Voight torque converter type clutch.

 

[JorgensenSteam]

Don-

That is some nice switchgear.
With the advent of AC drives (VFD's), I really don't see DC motors any more.

I think if you need near full torque and speed regulation down to almost zero rpm's, probably DC motors are still the way to go.

Here are 6 - 2000 hp synchronous motors at a local rainwater runoff lift station.
Originally built around 1945 by the Corps.
Not really large motors by industrial standards, the local refinery has a 32,000 hp motor.

I had a proposal to renovate this station, and although the switchgear and motors are considered modern in that they are all dead-front, etc, the wiring diagrams do not use standard symbols, and the nomenclature is very misleading, such as the label "vacuum breakers".
You would thing vacuum breakers would be the electrical variety, but no, they are actually pneumatic valves on the large water pipes that open to prevent siphoning of the water through the pipe.

A couple of smaller motors also at 500 hp and 300 hp.

It is an interesting combination of equipment, with GE 2000 hp motors, Westinghouse switchgear and motor-generator sets, and a Fairbanks Morse 300 hp motor.

The motor generators use an AC motor to drive a DC motor, to create the DC field for the 2000 hp motors.

The synchronous motors have two medium voltage breakers per motor, for a partial winding start. I have not seen partial winding start synchronous motors other than these.

 

[JorgensenSteam]

Motor generator sets.
The field current is adjusted using the motor-driven wiper arm on the contacts on top of the DC switchgear.

 

[JorgensenSteam]

The motors turn pretty slow, 240 rpm.

 

[JorgensenSteam]

Lots of "yikes" moments with this floor mounted, oil-filled transformer, with exposed secondary terminals. Not only is is a fire hazard, but to add insult to injury, it is the PCB type.

 

[JorgensenSteam]

And the ladder diagram for one of the 2000 hp motors, with non-standard symbols.

The "vacuum breaker" is a pneumatic valve, not an electric circuit breaker.

The motor starts by closing the medium voltage breaker on the far left (line breaker), which uses 1/2 of the windings to get the motor spinning as an induction motor. When the speed reaches a certain point, the second medium voltage breaker closes (running breaker), energizing the second half of the windings, and then the DC field kicks in and if you are lucky, the motor locks into synchronous speed.

 

[JorgensenSteam]

Pump down in a room below the motor floor.
All the 2000 hp motors have forced air electric heat to keep the coils dry, and all the heaters have run continuously since 1945, which is why these motors still operate on their original windings.

 

[Don1966]

I love that stuff I guess because I am for the old school. I cut my teeth on DC when I started this business, synchronous motors and wind rotor motors. I have rewinded many different motors also before I became a Tech. Some of your photos remind me of the old Ward lenard system. They used those on cranes and machinery. I still run across ampidynes used on old cranes, the military used them on gun terrets.
By the way the VFD,s have overcome the speed issue you can get 200% torque at zero speed with these systems.

Don

 

[JorgensenSteam]

Don-

That is interesting about the new VFD's. Did not know that.

I did a project one time in a small southern city, and they were renovating an old power generating building. You know you are going back when you open the panelbaord and see bare bus bars.

Note the knife switches for each circuit.

 

[JorgensenSteam]

This powerhouse was like a museum. The stuff that was casually stored up stairs included the following Ediphone. It looked as if they quit using it last year or something. I did a double-take. "What the heck is that?" I said.

 

[JorgensenSteam]

So I thought to myself, the project will have to wait, I am going to look at everything here.

The next item I found was a transformer looking thing, but with an odd moving coil.
Turns out it was used to change the voltage on the street light circuits.

Definitely a museum.

 

[kf2qd]

Was working on a Plasma table up in Milwaukee and they were working on some new pumps like these. 10 foot diameter tube size.

Having had family members that worked with those old transformers I think the danger from PCB's has been way overrated. No statistical difference between the workes at GE's shop among those that reworked those transformers than the general population. You stand more chance of being injured by electricity than by those PCB's.

 

[JorgensenSteam]

I read once about the statistics surrounding commercial airline crashes, but as I recall, you are much more likely to be killed by a lightning strike, or even a bee sting, than to perish in an airplane crash.

We always played with the sheets of asbestos that Dad brought home.
And we broke open those old thermostats, and played all day long with the blobs of mercury.

 

[Don1966]

That is differently some old stuff. I wish I would have kept some of that when I started. Really it don't seem that long ago when you look back, of coarse I am telling my age here. Thanks for sharing that with me Pat I really enjoyed your photos it brings back memories.

Don

 

[Mainer]

@kf2QD, UNIcastings:

Dismiss the health risks if you want. Look up what happened at the Johns-Manville asbestos plant.

Hatters used to use mercury as part of the process for treating felt. Ever wonder where the expression "Mad as a hatter" comes from?

Some of that stuff is increased risk, not a certainty, which can give a false sense of security. When you lose the roll of the dice though, the odds for you suddenly become 100%, and it's no fun at all. I've got Parkinson's disease. I don't have the genetic predisposition to getting it. Although one can only guess, I think it is probably due to a lot of exposure to carbon tetrachloride when I was a kid.

 

[JorgensenSteam]

Mainer-

Nope, I don't dismiss the health risks.
I think exposure to a variety of toxic stuff is what got my Dad.

It is just that I have been exposed to so much junk that I can only laugh about it, knowing that I could drop dead any day from it.

We just did not know any better.

The stuff mentioned above was some of the more safe stuff we did as kids.
Why I am still around, I don't know. We did some crazy stuff as kids.

Pat J