Good point... a single-phase AC motor would be a terrible choice, although a VFD could run a proper 3-phase motor from a single-phase source. Rationally, of course, it would be a 3-phase inverter running from a DC source.
Diesel / Electric Locomotive Technology
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No, I think he's planning on
1PH generator [1PH AC] -> VFD [AC-> DC -> 3PH AC] -> induction motor
because the generator is a 4-pole alternator driven at the required speed (1800 RPM) for 60 Hz.
Then if that's what you're copying, why not do that? In this locomotive design, the engine does not run at a fixed speed, and so the AC power is not at a fixed frequency.
You are missing absolutely nothing.
This frustration is the problem with trying to help someone design a system when they do not have even the most fundamental understanding that the power into anything must be at least as much as the power out, and that all of these components are transferring and transforming power. The average person probably does not understand that... but the average person doesn't try to design a powertrain.
No. Whether the motor is DC or AC, the power input to the motor must be greater than the output power (because it is not perfectly efficient). All modern EVs use AC motors, but some DIY projects still use DC motors, and this has nothing to do with the amount of power needed from the generator.
Size and voltage of a battery are unrelated. The choice of voltage and choice of controller and motor (and generator and its controller in this case) are tied together. Valid choices using available components can be as low as 48 V and as high as 800 V.
Battery size is related to energy capacity, and safe power output is proportional to energy capacity for a given battery type.
To explain this, "C" rate is the ratio of power (in watts or kilowatts) to the energy capacity of the battery (in watt-hours or kilowatt-hours), so discharging at 5C means using up all of the battery's capacity is 1/5 of an hour.
In his example, cricketo is dividing the required power (40 kW) by the "C" rate (5) to get the required energy capacity of the battery (8 kWh), and providing examples of charge capacity and voltage which come out to that energy capacity. To put a scale to this size, it is on the small end of the range of battery capacities used in plug-in hybrid cars.
No, the intention is not perpetual motion (or "over-unity gain"); the original poster is just working toward understanding that.
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5,820 Posts
A 80% generator connected to an 80% motor has 36% losses as heat. Throw in your 30% efficient ICE and you're at 81% as heat loss and 19% of the thermal energy being propulsion. Ignoring gearing losses.
A 33% thermal efficiency coal plant charging a 95% efficient battery, discharging at 95% into a 98% inverter into a 95% motor means 28% of the thermal energy goes to propulsion, 72% is heat loss, of which 67% is at the coal plant.
Now, do the math with wind and solar, which are FREE feedstocks.
Energy is $$. You save NOTHING by running a small, inefficient, heavy, engine, except an Arab's bank balance.
Your money is better spent with solar on the roof or building a wind turbine out of that 10kW generator.
A 33% thermal efficiency coal plant charging a 95% efficient battery, discharging at 95% into a 98% inverter into a 95% motor means 28% of the thermal energy goes to propulsion, 72% is heat loss, of which 67% is at the coal plant.
Now, do the math with wind and solar, which are FREE feedstocks.
Energy is $$. You save NOTHING by running a small, inefficient, heavy, engine, except an Arab's bank balance.
Your money is better spent with solar on the roof or building a wind turbine out of that 10kW generator.
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326 Posts
there was a hollywood start who had a turbine/generator electric hybrid car. I cant remember who it was. I was thinking Danny DeVito, I also remember that it burned to the ground after being parked. anyway, using a micro turbine seems to be the path for self generated electric hybrid. still seems like a huge waste to sink that cost of development since most cars are driven locally anyway.
study
study
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47 Posts
@428RC sorry to be offtopic but that 'microturbine because of its low weight' reminded me of finding out about that particular truck some time ago .. wasn't difficult to find some tidbits for it again for you and others here so here..
18wheelbeauties.blogspot.com
the fact that the turbine barely even was visible through the conventional with-sides-off hood is amusing but mm yeah
TBT - Turbine-powered Kenworth-Boeing - 1950
In true social media style, I figure Thursdays should be about #tbt trucks. I love pics of old trucks, what better opportunity than to join ...
18wheelbeauties.blogspot.com
the fact that the turbine barely even was visible through the conventional with-sides-off hood is amusing but mm yeah
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5 Posts
I was just making a one line pithy comment alluding to the lack of understanding the OP seems to have about efficiencies that you and Remy have done a much better job of describing with figures!
I genuinely don't understand what the OP hoped to achieve - remove a very efficient transmission, replace it with a generator and electric motor and somehow gain improved efficiency.
Obviously, unless you are prepared to accept significantly inferior road performance your diesel engine is going to have work harder than before you removed the efficient manual transmission.
The above statement ignores the application of any "magic beans" of course.
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2 Posts
Don't let "know it all people sway you from your path. and those that MIGHT know more than you or me but offer no advice need to move on to a porn site for all the good they have helped you with. I THINK IT IS A VERY GOOD IDEA. Maybe if you put 12 small lightweight 12 volt battery's in somewhere as a buffer. And don't even reply to those who don't offer advice.
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5,820 Posts
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18 Posts
Looks like you’ve got some decent background on your conversion idea. Locomotives generally use two stage ac-dc electric motors to manage the enormous torque, speed (and braking) requirements needed for modern train weights and acceleration requirements. Also locomotive applications have substantially different traction characteristics than EV’s. Coefficient of friction and train resistance are entirely different than automotive applications. Sounds like you don’t necessarily want to closely model a freight locomotive configuration in your conversion, but are more interested in the general concept of mating a traction motor with your existing diesel engine. You could explore the miniature train hobby to find the answers you seek. Chaski.org is the go to website for 1/8th to 1/3 rd scale train builders. Lots of people there have vast experience building small scale diesel electric drive chains. These would all be very similar to what you wish to accomplish. Except that most people do so with a ICE. Diesels have different power curves and speed requirements than ICE engines. So there can be some benefit in using the transmission to select a desired gear ratio for your diesel drive chain and wheel speed. With an ICE you often can eliminate the tranny and go with direct drive. Iam not experienced enuf to know what is best for your chasis and particular drive chain.
In any event, on Chaski, you get a lot of answers won’t be subject to the insults and useless, demeaning crap that a few keyboard warriors on this board love to deliver.
anyway, good luck!
In any event, on Chaski, you get a lot of answers won’t be subject to the insults and useless, demeaning crap that a few keyboard warriors on this board love to deliver.
anyway, good luck!
Great tip!
I can save people a few steps of run-around - this is presumably the target forum:
Live Steam & Riding Scale Railroading
(a forum for trains within a larger forum of "The Home Machinist!")
and within that more specifically
Riding Scale Railroading
"ICE" means "Internal Combustion Engine"; both gasoline-fueled and diesel-fueled engines are internal combustion engines. You are referring to the difference between a gasoline engine and a diesel engine, not between an ICE and a diesel engine.
Yes, diesel engine control is a bit different from gasoline engine control, but externally it is fundamentally the same: changing throttle valve opening of a gasoline engine and changing injection setting (pump rack position or electronic input) of a diesel engine have essentially the same effect.
Most of the difference in power curve shape between typical gasoline engines and typical diesel engines is simply that in most applications diesels are turbocharged and gasoline engines are not. Of course each engine has its own operating characteristics, not the same as every other engine burning the same fuel.
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18 Posts
Yes, correct. Thanks for clarifying. I rushed the post as we are traveling and dog tired from jet lag… what I was trying to get at, but didn’t really say was the OP would probably be better off using a controller to operate his proposed electric traction motor rather than trying to vary the frequency through the output from his existing diesel.
chaski.org will get him to the section on the forum that deals with the miniature train builds (I moderate the grand scale 3”,4”,5” scale pages).
chaski.org will get him to the section on the forum that deals with the miniature train builds (I moderate the grand scale 3”,4”,5” scale pages).
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