Quick Question re: Inverter

With modern advances, such as IGBT'S, HVDC is proving to offer lower losses

I don't think anybody could have predicted semiconductors 100 years ago. One huge advantage of HVDC is that you don't require three wires, eg three phase. A bipole HVDC system is far simpler, as rectification/inversion is now solidstate

 

Keep in mind for a given power capacity, HVDC produces negligible EMF. The biggest challenge to HVAC is right-of-way, as higher voltages produce much higher EMF

 

Precisely. A static magnetic field is not a producer of EMF, since the frequency is zero. In addition, a two wire HVDC transmission line has balanced current going in opposite directions on the two lines, so the fields tends to cancel.

Tom

 

Can you walk under a HVDC power line with fluorescent tube and have it light up?

 

I tried that stunt in a demonstration lab, and mine stayed dark. This was only approx 500 kvdc. Keep in mind a HVAC power line radiates EMF that will excite a fluorescent tube. As a HVDC power line has negligible EMF emissions, the stunt probably will not work

 

Correct. A two wire HVDC is also called a "bipole" which I referred to in earlier posts. I should get in the habit of explaining these terms

I bet after 5-6 drinks, we would have great engineering discussions.

 

I know this (the bipole thing). I was explaining some of the details for the benefit of any readers.

My education is in electrical engineering, so I have general idea about the basic concepts (E=IR and you can't push on a rope).

Tom

 

You would need a very high field gradient. It would be fatal if you were carrying the tube.

Tom

 

I would go so far as to suggest they are world leaders. That is my opinion, based on personal experience

I frequently travel to the EU on business. If I'm in London, I usually stay at one of the hotels at Canary Wharf, usually the Marriott West India Quay. I think the Underground operators have improved ventilation quite a bit, I rarely smell ozone

I would think the particulate matter from the rails is a more serious health concern. Eg, wheel-to-rail contact. Also, there are probably fine organics such as silicas from the brakes.

Let's not forget that humans are about the filthiest creatures on the planet. Can you imagine the decades worth of dead skin cells coating the floor of the tubes? Proper ventilation is a good fix for these issues

 

Correct. It was a safety demonstration of the system. Surprisingly, a lot of folks assume HVDC radiates the same "energy" as HVAC

Most likely, it wouldn't be possible to achieve the field gradient you suggest. The insulators aren't rated for it, they would break down and flash to ground

 

Yes, we make a good team. We just need to synchronize a bit better

 

Oh no! Synchronous DC. What does it mean? I'm so confused.

Tom

 

A-ha, clever bugger!

Here, have a drink on me

Gluk-gluk-gluk-gluk-gluk-CLINK

 

So, is HVDC actually now being distributed or still a concept?

 

There are some HVDC transmission lines. It's been in service for many years, but only on a limited basis.

Tom

 

Yep -- here's one in Canada.

New Zealand introduced an early HVDC applications in 1965 with undersea cables between the south and north islands. They used giant mercury arc valves to do the conversion.

 

They are in use all over the world, and as stricter EMF guidelines are introduced, they will gain in popularity

What held back HVDC for a long time was the need for mechanical/electromechanical rectification and inversion. Now that IGBT's are durable, and much cheaper than they used to be, HVDC is proving to offer efficiency and cost savings advantages over HVAC

 

For those curious, IGBT stands for Insulated Gate Bipolar Transistor. IGBTs are essentially a normal bipolar power transistor with a built-in MOSFET driver. This combines the high input impedance of a MOSFET with the low saturation voltage of a bipolar transistor.

Tom

 

Erp. Ok, I promise to do a better job explaining these topics.

 

Sorry guys, you went way past my curiosity level, LOL. And thanks for answering the lighting parlor trick question, I thought it might lighten the subject slightly although I think I failed there.