Electric drive Cat scrapers??

[Countryboy]

Welcome to HEF randy448! :drinkup

 

[activeorpassive]

Horse power is horsepower and cannot be changed going through any kind of transmission device. As I recall the capacity of the electric motors in a locomotive are usually double the capacity of the drivers. In other words in order to ensure durability, the horsepower capacity of the electric motor is double the engine output horsepower. The motor could take producing 800 horsepower but the engine only put out 400 so the motor can take the high startup loads over a long period of time.

I ran and repaired Letorneau scrapers at one job I worked. They used diesel engines driving a generator with a clutch and five speed transmission behind the generator. These units did not use an electric drive system. The electrics worked the bowl lift, ejector and machine steering. Wire rope pulley systems driven by motors worked the bowl and ejector functions. They were very problematic in that limit switches were used to cut off power when a function reached the end of its travel. The limit switches often failed and the cables would be snapped like a piece of spaghetti. We were constantly replacing cables and switches as well as clutches.

Diesel electric haul trucks have been around for probably forty years or more. They work very well in dry conditions using good haul roads. Bring in copious amounts of rain and form deep mud and they develop the types of problems described earlier in this thread. They overheat and burn up.

Electric drives up until about 15 years used DC motors. I saw some large Haulpak trucks go into a coal mine here a few years ago that used AC drives. They haven't had the stall out issues that the DC drives did and I'm wondering why. Scrapers would be prone to stall outs all the time and in context of this disscusion perhaps the use of AC drives make sparkys possible for scraper use.

Does anyone have any input on this.

Yes, horsepower is horsepower...but torque was the topic. And torque can be divided or multiplied through various means.
There are plenty of DC trucks floating around, but their numbers are fading. DC voltage is easier to control, but the proliferation of cheaper Variable Frequency Drives is making AC motors the technology of choice.
VFDs have come a long way, and although higher in cost at initial setup vs DC applications, the advantages are greater after even a short time period.

AC motors are cheaper to produce, and usually require less maintenance due to the removal of brushes and slip rings. This factor alone rules out DC for use in larger horsepower applications (4,000+) There are brushless DC motors, but even they have a higher maintenance cost in the long run, due to the addition of the excitation field winding for the DC rotor's armature, as well as the addition of the necessary rotating diode packs to control the field current going to the main rotor's pole pieces.

AC drives can provide 100 percent continuous torque (not HP), even at zero RPMs. This should account for the reduction of stall outs. DC drives can vary torque, but can not maintain constant torque through varying speed ranges.

DC motors will "run away" if one of the stationary fields are opened. While not a concern while the motor is under heavy load, a DC motor that runs away under light to no loads will continue to increase in velocity until it destroys itself. This is hazardous to not only the motor, but the attached load and any personnel in the area.

AC still has faults. The system has a higher initial cost (as mentioned earlier). The space requirements are also greater. In the world of big trucks, production is King, and space reduction due to physical size usually means payload reduction. Poor VFD design or application can lead to nasty voltage harmonic imbalances, which will eventually lead to premature failure. Regenerative braking is not inherent to an AC motor's design, so passive elements must be used to retard the energy created under coast conditions.

Both technologies have their place. There are still mines that employ both technologies and will spend the time and money to keep their DC trucks in production. I believe in the long run it all comes down to intended applications, ability to support maintenance/tooling, and perceived advantages.

 

[Jessikah]

Hmm that is interesting

 

[JASON M]

Maybe I was gone that day at school when they taught us how a 400 HP engine could provide 800HP at the wheels:spaz
Something don't sound right about this

I'm with you on this; Losses will be incurred. Horsepower is the rate at which work is done. You can't convert 400 hp into 800 hp............ but you can definitely convert 800 hp into 400 hp with driveline losses (in theory)

 

[surfer-joe]

Hmmmm. Takes about 400 horsepower to make 350KW. For a machine the size and weight of a 657, and to make the required speed on the haul is going to require more than 350KW. The standard engine in the 57 is about 550HP in front, 450 in back, about 1000KW. To retain the capability of the now existing 657 means the KW rating from a single engine on an electric drive 657 would need to be about 1300HP.

WABCO built a double barrell elevating unit in the early seventies that had a V12 Detroit fore and aft. It went like hell and loaded very well. I believe the engines were about 425HP each. 850 HP in all, and that machine was about the size and capacity of a 633 CAT.

LeTournau electric drive loaders and trucks in the early nineties used 150-200HP wheel motors in the rear wheels on the trucks, all four on the loaders. Minimum engine size was about 2000HP on the trucks (150 tonners), and about 2500 on the loaders (L1100).

I'm no electric expert, just have a little experience with a few electric drives. All in all, I'd rather have the mechanical setup as is.

Fun speculation, be interesting to see if more info comes out of CAT, or maybe in CE.

 

[Gavin84w]

Cat ED scrapers, agghhh no. EOS

 

[JTL]

This is kinda of an old thread, (started in 2007) but Im glad it got brought back up, after all it is 2010 now!:drinkup

Very interesting topic. I actually think I learned a thing or two about electric motors this morning! I had a mechanic working for me last summer that use to work in a coal mine in western Washington state. He was explaining to me how the haul truck drives worked, but I kept getting confused. After reading how the work, I kinda understand now. Might be interesting to see Cat try this concept. Although I not belive now is the time to try it with the economy the way it is.

On another thought- since it is 2010, and our president is black, I want to know one thing. WHERE THE %@&* IS MY JET PACK!!

Jason

 

[Gavin84w]

Cat is hurting a lot i think and keeping the company afloat profitably is priority No 1. I would think a lot of development projects have been cancelled. Think how many 793,s they sell vs scrapers and they have canned the electric drive 793 for the moment.

New product introduction always comes with a premium % higher cost than the previous models sold and with scraper prices today and higher prices for new models in the future a certainty i don,t think we will ever see ED scrapers from Cat, who would they be trying to keep in front of with a higher technology?

 

[Greg]

Makes sense to do it. The reports on the new D7E's being tried are all good. Reports are 20% less fuel than previous models and more push. I don't know why it has taken so long to get to this point as rail road locomotives have been doing it since the 1940's.

 

[OC(Outside Cat)]

If I remember correctly, Cat bought a company a few years ago,that used electric drives in something, (might have been a haul truck company) I thought at the time it would be interesting to see how they would use the electric drive set up.

OC

 

[malcolm]

electric scrapers

May bee after 50 years cat are going to make a crowd pleaser like this cheers malcolm

 

[Miner89]

Hybrid Mining

hi,, new to the forum so not sure if this is the correct place


im looking for information on hybrid mining machinery and if there is any results on testing phases available


thanks all

 

[stangoodman]

Hey Malcolm'

Was the pacemaker photo from Rotorua. As far as i know there was only one brought into NZ and operated out of rotorua, but I can't remember by who?

Regards

Stan

 

[RDG]

H. Allen Mills were the ones who had the pacemaker in Rotorua, I remember seeing it when I was a kid TEXAS ROSE was her name from memory. Cheers RDG

 

[markshr151]

Everything old is new again.
how about diesel/flywheel/gen. for max intermittent power?