[IamIan]

Originally Posted by DavidDymaxion

All I have to do is draw some power from the batteries while holding the brakes, and observe the car didn't move -- therefore there can't be any energy put into linear or rotational motion; it is similar for power.

very close.... but I think you missed a little bit .... there is still energy put into rotational motion... even if there is not a net motion... just because the energy put into the motion is not enough after losses to overcome the brakes does not negate the presence of the energy still being applied.

In short just because you put energy into doing something does not necessarily mean you actually will do something.

I put put forth my own personal energy but I will not be able to lift a skyscraper , not even a tiny bit... and even if there was no motion, there was still energy over time which is a definition of power ... and there was still energy converted which is another definition of power even if there was no motion at all.

Originally Posted by DavidDymaxion

While it is correct that you could measure the heat and assume any missing heat goes to some other form of energy, in practice that is hard to do accurately. In this case it is far easier to observe there is no useful output power (motion).

Maybe there was confusion in saying there was no power. To clarify, you have electrical power going in, and power going out as heat, but no useful power in terms of motion.

I would agree there is no apparent macro motion... which is a major reason why I think this kind of discussion is mostly academic ... people just want the car to go... exactly how the electrode works or the nature of electron drift may all be 100% correct things... but they are still 99% academic to the application for 99% of EV builders.

Macro motion is only one way of determining the presence or absence of power... remember power does not require motion... there is power any time there is energy converted...there is power any time there is energy over time.

Also ... although it is also an academic point... temperature is motion.

Originally Posted by DavidDymaxion

If you vary the current, or voltage, or frequency, different things might get hot (possibly including air itself from arcing), but all that battery power is going to waste if the vehicle is not moving. Almost all of this loss is heat, a little bit might go into sound or flexing things.

Kind of... I was referring to a different angle...

It is already commonly known to most people who work with electricity ...that it is the flow of / movement of electrons that causes heat when it passes through a electrical resistance... Voltage is a current driver but voltage does not itself cause heat.

Although 10V @ 1 Amp and 1 V @ 10 Amps are both 10Watts... if you pass both of those through the same amount of resistance the 10 Amps will produce significantly more heat than the 1 Amp will... about 100x more heat actually.

This is one of the reasons higher voltage systems can use thinner wires to carry the same power.

If 100% of the power going into an electrical motor is all lost... where did it go?
If it went to heat than both the 10V @ 1 Amp and the 1V @ 10 Amps would both have to generate equal amounts of heat... when it is already known that they do not... If it was converted to something else... what was it?

No matter what it is converted from or to... energy conversion is power... if it happens over time...energy over time is still power.

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From a EV build perspective very little if any of this matters.

People care about the peak requirements and the continuous requirements.

Peak requirements of the motor , electronics, batteries, etc...

Continuous requirements of the motor, electronics, batteries, etc...

So a EV builder doesn't really care if there is or isn't power at 0 RPMs... at 0 RPMs he wants some specific things weather there is or isn't power.... he doesn't want to damage his EV components from heat , abuse , etc... he wants to be able to pull out from 0 RPMs at some rate of acceleration that he is happy with... that's it.

It doesn't matter if there is still 60% or more of the power than was applied... or 0% of the power applied.... as long as it does what he wants it to do the EV builder doesn't care.

As it was pointed out previously in the thread... there are methods of working out the acceleration and such of a build either form a torque or a power perspective.

If you are happy with the results of the build ... I don't see how it matters... do it which ever way you like to do it... either way gets you to a EV... so everybody wins

[major]

Originally Posted by IamIan

If 100% of the power going into an electrical motor is all lost... where did it go?
If it went to heat than both the 10V @ 1 Amp and the 1V @ 10 Amps would both have to generate equal amounts of heat... when it is already known that they do not... If it was converted to something else... what was it?

IamIan,

"If 100% of the power going into an electrical motor is all lost" then it would be a stall condition, meaning zero RPM, and zero mechanical power output. There could be torque on the motor shaft. In this condition, yes, the input energy (volts * amps * time) is converted to heat.

In your example, 10 volts @ 1 Amp, means the motor resistance is 10 ohms. And the input power is 10 Watts. And the energy converted to heat is 10 joules per second. Now how can you get this 10 ohm load to conduct 10 Amps at 1 volt?

Now if you allow the resistance to change, then 10 volts @ 1 amp will produce exactly the same heat as 1 volt at 10 amps.

The physics of this is clear. No motion, no mechanical power. Period. Now there may be power converted to heat or otherwise, but it is not mechanical power.

Just replace the motor with a torsion spring. It will have a torque on the shaft. Right? And it will stay there, essentially forever, without any power input, without any heat. So force (or torque) can (and does) exists without motion, and therefore without power.

Regards,

major

[IamIan]

The Ohms has to stay the same.
So a 1 Ohm resistance ( not reluctance , or impedance, etc. ) when exposed to a 10 VDC electrical source can drawl up to 10 Amps... If we supply a conventional 100V electrical power source it would go up to 100 Amps... but Amps are just the average flow of electrons... so we use a PWM power supply to put out 100V at 1 Amp to the 1 Ohm circuit...

Now both are passing 10 Watts of power through the 1Ohms ... but it is well known and well documented that even at the same power ... the 10 Amps of higher current will always produce more heat at the same resistance... the 100V at 10 Amps will produce the same heat from that 1 Ohms of resistance as 10V at 10 Amps.

Amps of current drive the heat... Voltage effects power... but Voltage does not directly effect the heat at all... heat generation from electricity is a product of the resistance and the current... Voltage is not involved.

If 100% of the power was converted to heat than both the 1 Amp and the 10 Amps would both supply the same amount of heat as both have the same amount of power ... but that is not what happens... the heat is driven by the amps not the volts or the net power... which shows that more of the power is not lost to heat when one has higher voltage.... which turns out to be 100% correct... this is a very old very well known phenomenon of current and heat generation.

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Originally Posted by major

Just replace the motor with a torsion spring. It will have a torque on the shaft. Right? And it will stay there, essentially forever, without any power input, without any heat. So force (or torque) can (and does) exists without motion, and therefore without power.

The major flaw with the spring example is that there is no energy conversion with the spring while it is held stationary ... and there is no energy flow over time while it is held stationary... if you had both of those with the electrical motor it to would have zero power at zero RPMs.

In the spring example... it is not because there is 0RPMs that there is no power... there is no power because there is no energy conversion ... and no flow of energy over time.

That same thing is not true for the electrical motor... In the electrical motor there is energy flow over time... and energy conversion... either of which mean you have power even at 0 RPMs.

Originally Posted by major

The physics of this is clear. No motion, no mechanical power. Period. Now there may be power converted to heat or otherwise, but it is not mechanical power.

Originally Posted by major

. Period.

That's allot of periods...
But I still disagree.... even if I also still say it is just an academic discussion.

Now I will grant you... that if you want to just ignore the power at 0 RPMs for one reason or another... fine... but weather you want to ignore it or not... there is power there.

Even if you begin to exclude lots of things ... like when you say mechanical power you are also ignoring any perpendicular motion ... if at 0RPMs the electric motor caused the whole vehicle to move perpendicular to the rotational axis ... by the excluding rules of mechanical power that motion doesn't count and it would still give a result of 0 even if the whole EV is moved at any acceleration or speed you like, because as soon as you say mechanical power you exclude all perpendicular motion ... which just shows how silly it can get when you start to just exclude things... Mechanical power also excludes any vibration that is perpendicular , etc... it is just a way of ignoring lots of things that are actually there.

If you want to ignore it fine... but it is still there.

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An other way to see that there is power at 0RPMs is the 'Instantaneous Power' ... Instantaneous Power is power with no time and no movement... ie 0RPMs because it is instantaneous and it would take at least some time to move, at any speed .... there is even 'Instantaneous Mechanical Power' ... or mechanical power without any motion and without any passage of time.

But that is even more academic than we have already been.

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I still hold that... it doesn't matter... find the rating for your components under the conditions you will use them... including pulling out on a hill from a stop... use torque or power... whatever makes you happy... if you like it easier and just want to ignore the power at 0RPMs... go ahead... I don't see how it will effect 99% of the EV builders either way... do it however you want... if you don't know enough about it.. ask others who have done conversions and or read up and or pay someone to do it.

[major]

Originally Posted by IamIan

Instantaneous Power is power with no time and no movement.

The quantity of power is an instantaneous value, just like velocity. It represents the work being done at that instant in time, just like velocity represents the rate of travel. As Tesseract said, this is one of the reasons Newton invented the calculus. To help us explain mathematically how his physics work.

You have said a lot, and if I have time, I'll try to expand more, because I find this interesting. But in short, I say you have nothing to offer here which would make me deviate from Sir Newton's view of our universe.

No offense, mate. And I hope that I interpret Newton's Laws correctly. Any support or corrections from the sidelines is appreciated.

Regards,

major

[major]

Originally Posted by IamIan

The major flaw with the spring example is that there is no energy conversion with the spring while it is held stationary ... and there is no energy flow over time while it is held stationary... if you had both of those with the electrical motor it to would have zero power at zero RPMs.

IamIan,

I think you said you agree with me

In the spring example... it is not because there is 0RPMs that there is no power... there is no power because there is no energy conversion ... and no flow of energy over time.

Energy flow over time???? Isn't that the definition of power? And it is exactly because there is no movement that the power, or "energy flow over time" is zero. Which came first, the chicken or the egg, the power or the motion?

That same thing is not true for the electrical motor... In the electrical motor there is energy flow over time... and energy conversion... either of which mean you have power even at 0 RPMs.

Yeah, but the energy conversion is from electrical to heat, not mechanical. So it is no different from having a resistor and a torsion spring. No mechanical work is done, zero power (mechanical). There is torque on the shaft and heat from the resistance. But the vehicle does not move. Yeah things get hotter, but so what. That is not what we're after, is it?

Regards,

major

[major]

Originally Posted by IamIan

The Ohms has to stay the same.
So a 1 Ohm resistance ( not reluctance , or impedance, etc. ) when exposed to a 10 VDC electrical source can drawl up to 10 Amps... If we supply a conventional 100V electrical power source it would go up to 100 Amps... but Amps are just the average flow of electrons... so we use a PWM power supply to put out 100V at 1 Amp to the 1 Ohm circuit...

Now both are passing 10 Watts of power through the 1Ohms ... but it is well known and well documented that even at the same power ... the 10 Amps of higher current will always produce more heat at the same resistance... the 100V at 10 Amps will produce the same heat from that 1 Ohms of resistance as 10V at 10 Amps.

Amps of current drive the heat... Voltage effects power... but Voltage does not directly effect the heat at all... heat generation from electricity is a product of the resistance and the current... Voltage is not involved.

If 100% of the power was converted to heat than both the 1 Amp and the 10 Amps would both supply the same amount of heat as both have the same amount of power ... but that is not what happens... the heat is driven by the amps not the volts or the net power... which shows that more of the power is not lost to heat when one has higher voltage.... which turns out to be 100% correct... this is a very old very well known phenomenon of current and heat generation.

IamIan,

This is simply incorrect. I have argued with you on Newton's Laws. Hopefully someone else can help and explain Ohm's Law

Regards,

major

[IamIan]

Originally Posted by major

IamIan,

This is simply incorrect. I have argued with you on Newton's Laws. Hopefully someone else can help and explain Ohm's Law

Regards,

major

I was aware of all your points so far on Newton's Laws before you posted them.... so you haven't said anything new to to me.

Nor has anything yet been said about Ohms laws that I was not already aware of.

But it isn't needed for us to 100% agree with each other... As I've have said from the beginning it's an academic point... and I don't see how it would effect a EV builder in real world application.

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You started saying there was no Power at 0 RPMs.

That statement is still incorrect.... even if as I have said from the beginning it is an academic issue and doesn't effect application... and even if you have sense silently abandoned that incorrect position.

Your own quote from Wikipedia disagreed with you on power.

Your own quote from Wikipedia disagreed with you about power and the stationary spring example.

You changed from your original position ... and instead of admitting there is power you claim that you just want to ignore any power that isn't 'mechanical power'.

I still say that is fine and the discussion is academic but point out some of the short comings of invoking 'mechanical power'... for instance Mechanical power also ignores more than just non-motion power... it also ignores any motion that is perpendicular to the applied force.

Even if you only care about 'mechanical power' that still doesn't mean that there aren't other types of power present that you just want to ignore.

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As easy as Newton's laws are ... don't forget progress has been made sense 1687 when he published them , and they are no longer considered to be scientifically 100% correct... they are simplified expressions of much more complicated interactions that do not always obey his 320+ year old understanding.

As easy as Ohm's laws are ... don't forget progress has been made sense 1827 when he published them... they are no longer considered to be scientifically 100% correct... they are simplified expressions of much more complicated interactions that do not always obey his 180+ year old understanding.

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What I stated is correct, current and resistance are the drivers of electrical heat ... Voltage doesn't matter. It has been a very well known implication of electrical wiring for decades.

Here is another example that might help to illuminate this point about the power is not all converted to heat.

Make a Electric motor out of superconductive materials ... which has already been done at least on the research level... apply this EV motor with brake on to 100 kW of power... the brake may stop the motor from turning and there would be 0 RPMs... but there would also be almost none of that 100 kW of electrical applied power converted to heat... Where did the power go? ... Hint this is the same place a portion of the power goes from a normal electric motor with resistance used in this method.

If the idea that all the watts of power are converted to heat were true it would force the superconductor to heat up with that 100 kW ... but that isn't what happens.

Originally Posted by DavidDymaxion

Don't forget, if you PWM you get less average voltage. 100 Volts with a 10% on / 90% off PWM means you'll get on average 10 Volts. Armed with this knowledge, you'll see you get the same heat numbers and no mysterious differences.

That is a very good point ... and I agree my PWM example is obviously flawed.

It isn't mysterious ... It is just counter-intuitive.

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Now using Ohm's laws ... consider a superconductor with 0 Ohms ... it can have a current even while there is no Voltage... 0 V = 10 Amps * 0 Ohms ... or that same superconductor can pass 1,000,000 Amps .... 0 V = 1,000,000 Amps * 0 Ohms.... the super conductor can carry electrical power ... there is still a flow of energy ... even if there is 0 V there can still be electrical power.

In short Ohms' laws and Newtons' Laws are very useful ... but neither one has been 100% scientifically correct for many many years.

We know more today than they did back then... so they and their outdated laws are sometimes wrong, or miss things.

[ZX-E]

All major was saying is there's no mechanical power output at 0 RPM...

[major]

Originally Posted by ZX-E

All major was saying is there's no mechanical power output at 0 RPM...

Well said, ZX-E. I don't see what is so hard to understand about that.

Thanks,

major

ps. BTW, this makes torque relevant.

[Duncan]

IamIan

I don't know what you have been smoking but at human scales Newtons laws still work fine you have to be very small large or fast to detect the difference between Einsteinian mechanics and Newtonian

To your superconducting motor
While it is held at zero speed it will do zero work and consume zero power
As soon as you let it go it will do "mechanical work"and consume electrical power
If there is no power source the current in the coils will drop as work is done
No Magic!

The advantage of superconducting motors is that they should be able to be made much smaller
(Useful for a ship)

For my car I want mechanical power!

Other types of power will not move metal!

You can use the other types of power (Spiritual?) for your car if you want