transmision in big wehicles like mining dump truck
transmision in big wehicles like mining dump truck
(OP)
They use either planetary gears with torque converter like cars do or diesel electric like diesel lcomotives.
None uses hydrostatic transmision like excavator does with variabile displacement axial piston pump and fixed displacement axial piston motor.
if we look overall transmision efficiency for:
1. electric transmision
alternator has power factor round 0.85,
inverter has efficiency round 0.9,
induction motor has power factor round 0.85
so overal efficiency is 65%
2. automatic transmision
torque converter has efficiency from 0 upto 80% (0 when stationary, 80% when speed sycronizes) and some is lost in planetary gearset as well so overall efficiency for dump truck would not exceed 60%
3. hydrostatic transmision
axial piston pump is reported to have 90% overall efficiency,
same goes for fixed displacement axial piston motor,
up to 5% is lost in the valves and pipes
so overall efficiency would be 77%
So why they prefer diesel-electric or diesel mechanical transmison over hydrostatic?
None uses hydrostatic transmision like excavator does with variabile displacement axial piston pump and fixed displacement axial piston motor.
if we look overall transmision efficiency for:
1. electric transmision
alternator has power factor round 0.85,
inverter has efficiency round 0.9,
induction motor has power factor round 0.85
so overal efficiency is 65%
2. automatic transmision
torque converter has efficiency from 0 upto 80% (0 when stationary, 80% when speed sycronizes) and some is lost in planetary gearset as well so overall efficiency for dump truck would not exceed 60%
3. hydrostatic transmision
axial piston pump is reported to have 90% overall efficiency,
same goes for fixed displacement axial piston motor,
up to 5% is lost in the valves and pipes
so overall efficiency would be 77%
So why they prefer diesel-electric or diesel mechanical transmison over hydrostatic?





RE: transmision in big wehicles like mining dump truck
In, e.g., a bicycle, they can't compete with roller chain.
Haul trucks need suspension travel, so they'll need hydraulic hoses, really big ones, running at high pressure, which makes them expensive and short-lived.
Not to mention all the sliding parts running with very small clearances, also expensive.
Mechanical automatics got simpler with electronic computers instead of hydraulic computers, but they still have a lot of precision moving parts.
At thousand HP levels, electric propulsion is mechanically much simpler, and has to be cheaper, especially on a lifecycle basis.
Mike Halloran
Pembroke Pines, FL, USA
RE: transmision in big wehicles like mining dump truck
So mechanical over electric? Caterpillar 797 for instance uses mechanical, while Liebherr T282B uses AC electric asme goes for Hittachi EH5000.
Braking is also important on such big vehicles you can't just apply friction brakes or you'll destroy them quick.
Diesel electric locomotive uses induction motors for most of the braking, road trucks uses special valve in the exhaust port so engine takes most of the braking, how is with torque converter? Do they use same solution as road trucks with exhaust valve?
RE: transmision in big wehicles like mining dump truck
1. electric transmission
alternator has power factor round
0.85more like 98%,inverter has efficiency round
0.9more like 96%,induction motor has power factor round
0.85more like 98%so overall efficiency is
65%really 92%Keith Cress
kcress - http://www.flaminsystems.com
RE: transmision in big wehicles like mining dump truck
Power Factor = ( watts ) / (volt amps )
Power Factor = True power / Apparent power
Efficiency = Output / Input
RE: transmision in big wehicles like mining dump truck
RE: transmision in big wehicles like mining dump truck
Correct. But this speaks only to a relationship between leading and lagging of components of the electrical power - not about power consumption.
Correct.
Keith Cress
kcress - http://www.flaminsystems.com
RE: transmision in big wehicles like mining dump truck
Check it out - 40 years after the EE classes and I'm pretty close.
http://hyperphysics.phy-astr.gsu.edu/hbase/electri...
RE: transmision in big wehicles like mining dump truck
The reason power companies hate low power factors is because they simply have to have BIGGER equipment to handle the excitation current. They need bigger magnetic structures in all the transformers and bigger windings and cores in their generators, so they penalize users into either paying for the premiums bad power factors cost them or it incentivizes the users to correct their power factor.
The bigger currents needed to support the excitation can at second-order level cost a wee bit more fuel to support but it's scant and really something to be left out of this discussion when people are already missing the primary point that electrical power factor has nothing to do with the primary efficiency of electromotive functions.
Keith Cress
kcress - http://www.flaminsystems.com
RE: transmision in big wehicles like mining dump truck
In that application. I think that these were like an automobile auto transmission,Nike a fluid flywheel.
This must have been around 1985?
These excavators were BIG I remember having a meeting in a bucket!
Nothing against Diesel engines per se, but the actual duty of a large excavator is severe.
They would blast the quarry wall, then run the excavators at the debris, scoop up the rock, run over to a equally large dump truck and drop the load in. Repeat the cycle until rock gathered up.
So you would have a long idle, short high power run (to lift the rock) then low power run,
Few of these then a long idle, while they blast.
Not a good duty for a large diesel