P42DC HEP

[Peter KG6LSE]

hehe and yall have not taken in to account reactive power too as a 3 phase delta AC system. a little Cos here and TAN there and a power factor volla VARs VAs and WATTS ..

 

[PVD]

are they delta or wye connected? since the power factor for a particular type of railcar is probably very predictable (when ac is running vs resistance heat) it would be fairly easy to correct for if it was in any way going to create a capacity issue. (In the outside world, it could contribute to a cost/billing issue and might be worth correcting or mitigating regardless)) Probably not a big issue in this scenario, but certainly a commonly overlooked engineering issue in non electrical circles. just taught a class segment tonight on using energy storage to mitigate the effects of both power factor and peak demand billing penalties on electric bills........

 

[west point]

Power factor? ? Thought almost all 1 & 3 phase motors are capacitance wound to keep power factor unity ?

 

[PVD]

Probably not in older motors, but even if it wasn't, since it is relatively predictable, you would be able to build in correction into the supply circuit if it mattered anyway. .It doesn't seem to be a major issue in this situation.

 

[Peter KG6LSE]

HEP last I looked was Delta

the Delta 480Vto Wye 208/120 Transformer provides the needed consumer power at 120 and also 208 for motors heaters and lights.

the problem with non unity PF is it can wreak havoc on Inverters that provide it . IF the HEP system is slilcon based and its not some stupid genset then its not gonna like PFs of .8 or worse.

1.2kV DC HEP with DC-DC buck converters on every car is just about Ideal.

Very much like HVDC-Lite from ABB ect.

 

[jis]

I doubt that there is anything in the current cars that would screw up power factor badly enough to make it go below 0.8. But then again, this is Amtrak which has somehow convinced itself that over the long haul it is cheaper to keep the 25Hz electrification in place. So who knows what crud they have installed in the HEP cars?

There are possibly cars that are axle generating and able to be connected to EOG (End On Generation whether loco based HEP or using separate Generator Cars) in places like India. For them it would make sense to rectify the AC HEP feed after stepping it down to the battery bus voltage. Afterall they already have the alternator circuitry in place to take feed from the battery and supply it at appropriate AC voltages and in case of India 50Hz. Admittedly I have no idea whether they have such cars. they do have cars that are air conditioned and self generating from axle driven alternators and huge battery banks, and they have EOG powered cars. Possibly they are kept cleanly separated in separate consists. They mostly use diesel Generator Cars, though very recently they have been acquiring locomotive based HEP. But they still seem to keep a Generator Car in the consists for those occasions when for whatever reason the loco based HEP is unavailable.

 

[OBS]

I got a headache trying to understand all this HEP "stuff"...Did I miss out on anything? LOL

 

[jis]

Nah! It is all nerdy stuff that no one really needs to know, unless they actually have to design such things. But you already knew that we are a bunch of nerds here, didn't you?

 

[PVD]

A bunch of people (myself included) like dealing in the theoretical rather than the real world. In simpler terms, HEP matters because diesels are actually diesel-electric. They generate electricity and the more of it that gets used to power things in the cars, less is available to push or pull the train. Equipment to convert and manage this takes up space so it is a factor even for electric-electric locos (not diesel). There is another group of diesels called genset diesels where the HEP is generated by a separate unit, this takes up space "under the hood" that might house a larger prime mover. The power is sent to the cars via big cables that get connected when the train is made up. Power cabinets in the cars have equipment to regulate and manage the power for that particular car. There are other ways to provide and manage power in use in other parts of the world.

 

[Dutchrailnut]

the hep cables are 4 sets of 4/0 conductors, which limits HEP to a max of 1000 Kw.

yes it has redundancy , no one wants to burn up train wiring if one jumper fails.

 

[PVD]

Assuming they are special "fine strand" for flexibility. Before I retired from the field one of my last jobs involved a 1000 foot pull of 4/0 (3 phases, neutral and ground) in underground duct with multiple chambers. Not easy. But needed to be that large to keep voltage drop within limits. Almost smoked the pulling machine on more than one occasion, snapped rope a few times also.

 

[west point]

Lets put a consideration in here. On older heritage cars there were axel generators either belt driven or a transmission. So how much tractive effort went into the drag of these generators ? Pay me one way or pay another ? Would expect the electrical load of old equipment higher ?

 

[PVD]

I won't address axle generation, I'm not qualified, but from an energy standpoint we neither create nor destroy energy (fusion excepted), we only change it from one form to another. Think EPAS instead of belt driven off the engine on cars. Newer lighting and a/c is certainly more efficient, look at the results from the LED conversion on the Auto Train. Assume something newer would have better insulation, thereby reducing heating and a/c energy requirements. Looking at when most of the fleet was designed, there is a lot of room to improve on this subject.

 

[MattW]

Off-topic note, but fusion doesn't create or destroy energy either, merely converts it to/from matter.

 

[PVD]

I use the term "create" since it did not exist as energy, although it did exist. We use the term to differentiate from the release of stored energy, or change from one form to another ie: light to electricity.

 

[CCC1007]

And matter is only yet another form of energy, so same thing.

 

[jis]

And matter is only yet another form of energy, so same thing.

Extermely densely packed one at that. c squared is a very large number in E = m x c squared.

 

[Bob Dylan]

And matter is only yet another form of energy, so same thing.

Extermely densely packed one at that. c squared is a very large number in E = m x c squared.

I'm no Scientist but I play one on AU! And I heard on Fake News...

 

[jis]

And matter is only yet another form of energy, so same thing.

Extermely densely packed one at that. c squared is a very large number in E = m x c squared.

I'm no Scientist but I play one on AU! And I heard on Fake News...

Huh?