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Author Topic: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)  (Read 59493 times)

antijon

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #105 on: July 16, 2017, 12:10:53 AM »
Brad, I know why power increases when a motor is loaded. I also know that efficiency doesn't mean anything with motors under a few horsepower, I think they're all above 85% at least.

You're confusing two very different types of efficiency.

Efficiency 1: high impedance (cemf) results in little power being transferred to a load.
Efficiency 2: the ratio of power supplied and power being consumed by the load.

If you never run a motor at its full load, then I can see why you think cemf equates to efficiency. But in real motors with real loads, if you try to replace a motor with anything under the original motor FLA, it's not going to work.

For instance, two motors with matching RPM and HP:
1075 RPM .5 HP 6 amp FLA
1075 RPM .5 HP 9 amp FLA

The first motor pulls less amps so it seems to be more efficient, but if I'm replacing a motor that pulled 9 amps then I need to go back with 9 amps. I learned from experience. The 6 amp motor actually pulled 10 amps before it overheated.

So I'll say again, the current or power consumed by the motor is directly related to the power transferred to the load.

tinman

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #106 on: July 16, 2017, 01:27:51 AM »
Revolutions Per Second.


The desired event is to convert electrical potential into mechanical work, it is unfortunate that with the present methods of using the magnetic field interaction there is an opposing voltage created.


https://en.wikipedia.org/wiki/Ampere


There does seem to be a force to amps defined so there is an answer,,  :)

As i said before--the voltage is not apposing.
The BEMF produced in the self induction of the motor, is off the same polarity as that delivered to the motor.


Brad

tinman

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #107 on: July 16, 2017, 01:57:29 AM »
Brad, I know why power increases when a motor is loaded. I also know that efficiency doesn't mean anything with motors under a few horsepower, I think they're all above 85% at least.

You're confusing two very different types of efficiency.

Efficiency 1: high impedance (cemf) results in little power being transferred to a load.
Efficiency 2: the ratio of power supplied and power being consumed by the load.

If you never run a motor at its full load, then I can see why you think cemf equates to efficiency. But in real motors with real loads, if you try to replace a motor with anything under the original motor FLA, it's not going to work.

For instance, two motors with matching RPM and HP:
1075 RPM .5 HP 6 amp FLA
1075 RPM .5 HP 9 amp FLA

The first motor pulls less amps so it seems to be more efficient, but if I'm replacing a motor that pulled 9 amps then I need to go back with 9 amps. I learned from experience. The 6 amp motor actually pulled 10 amps before it overheated.

So I'll say again, the current or power consumed by the motor is directly related to the power transferred to the load.

Regardless of the size of the motor,or the load placed on it,an efficient motor has a higher BEMF under any load conditions--it is the quantity of BEMF that makes the motor more efficient.

I asked you if you know why a motor draws more current under load,and you answered -yes,i know why. But it would seem that you dont,or you would know that it is only the value of the BEMF that determines how much current the motor draws-whether it is under load or not.

So,why dose a motor draw more current under load?-->because the value of the BEMF drops.
As this BEMF value drop's,the potential difference between the supply voltage and self induced voltage become's greater,and so it is like i explained in post 120.

Quote
high impedance (cemf) results in little power being transferred to a load.

High impedance means that the BEMF/CEMF value is very close to the supply EMF value,and so,very little current flow's.

As i said,an efficient motor maintains the highest value BEMF under any load conditions,and here is what i mean-so as it is clear.

We have an electric motor-lets say a brushed DC motor.
Lets say that unloaded,this motor draws 1 amp at 10 volt's.
We know that when we place a load on this motor,the current draw will go up,and the only !only! reason it go's up,is because the BEMF value go's down(impedance decreases)-->this is why i asked you if you knew why the current draw go's up on a motor when you place a load on it.

Now,what if we could maintain the BEMF(impedance) value as we place a load on that motor?--what would happen to the current draw of that motor?--Thats right,the current would not rise,as the impedance value would remain the same.

So,do you now understand as to why a high BEMF value is important to efficiency?.


Brad

tinman

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #108 on: July 16, 2017, 02:04:41 AM »
85% for a small motor :)

More in the range of 50-75%,, some really small little ones as low as 35%

Ideal calculations would be energy in per second to torque out per second, torque in N-m =2piJ per rotation per N-m, 1J per second is 1W
torque=(I*V*60)/(rpm*2pi) for 100% efficiency. or
torque=J/(rps*2pi)

I have used a confusing phrase for some,, voltage drives current,, and as such an opposing voltage will act as a resistance to current flow depending on how much of the source voltage the opposing voltage is,, kind of simple really.
Inside every motor is a generator,, you have a magnetic flux that is changing relative to a coil that is observing it,, and it is this very generator that stops the motor from drawing the same amps and spinning up with the same torque to oblivion, as the speed of the generator increases the voltage it produces goes up and when it reaches the source voltage no current can flow.

If then the CEMF from the induction process inherent inside almost every motor were enhanced,, would that make it a better motor or a better generator?  How about if it were reduced?
Is the same torque at a higher RPM more or less power than at a lower RPM?

I think you can also see that the IR^2 losses might not be such a big thing.

Here is a simple answer for you.
Get your self a unipolar/homopolar motor,that produces no BEMF,and see how much torque you get in relation to the power you supply to it.

You now have your motor that has no BEMF, will spin up to self destruction speed,and draw a sh-t load of current ;)
You will also find it has very little torque-->you have a rotating heater.


Brad

citfta

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #109 on: July 16, 2017, 02:59:42 AM »
Some people just don't seem to be paying any attention.  So here is how to make you very own motor with no BEMF or CEMF, whatever you want to call it.  Take apart anything you want that has a universal motor in it.  The kind with field coils and brushes.  Now disconnect the field coils and apply whatever value of DC you want to the brushes.  I would suggest you start out with only 12 volts or so.  Now keep increasing the voltage as much as you want.  You will never get any torque from that motor.  The reason is because the same thing that creates the BEMF is the magnetic field of the field coils which are also the reason you get torque.  The same interaction that gives torque also gives you the BEMF.

In large industrial machines a lot of the time they use large DC motors.  These motors have the field coils powered separately from the armature.  Because of the BEMF generated these motors will of course reach a set speed with the field coils fully energized.  Now if there is a reason to want the motor to run at a higher speed than the bases speed then the current going to the field coils is reduced.  This in turns means less BEMF and the motor will speed up until the BEMF again balances out between the load and the applied armature voltage.  But you can only do this if the motor is not heavily loaded.  Otherwise the motor will lose speed because of the lower torque.

lancaIV

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #110 on: July 16, 2017, 02:05:58 PM »
https://en.wikipedia.org/wiki/Universal_motor
.....

Torque-speed characteristics

Series wound electric motors respond to increased load by slowing down; the current increases and the torque rises in proportion to the square of the current since the same current flows in both the armature and the field windings. If the motor is stalled, the current is limited only by the total resistance of the windings and the torque can be very high, and there is a danger of the windings becoming overheated.
The counter-EMF aids the armature resistance to limit the current through the armature. When power is first applied to a motor, the armature does not rotate. At that instant, the counter-EMF is zero and the only factor limiting the armature current is the armature resistance.
 Usually the armature resistance of a motor is low; therefore the current through the armature would be very large when the power is applied. Therefore the need can arise for an additional resistance in series with the armature to limit the current until the motor rotation can build up the counter-EMF. As the motor rotation builds up, the resistance is gradually cut out.
The speed-torque characteristic is an almost perfectly straight line between the stall torque and the no-load speed. This suits large inertial loads as the speed will drop until the motor slowly starts to rotate and these motors have a very high stalling torque.[5]

As the speed increases, the inductance of the rotor means that the ideal commutating point changes. Small motors typically have fixed commutation. While some larger universal motors have rotatable commutation, this is rare. Instead larger universal motors often have compensation windings in series with the motor, or sometimes inductively coupled, and placed at ninety electrical degrees to the main field axis. These reduce the reactance of the armature, and improve the commutation.[4]

One useful property of having the field windings in series with the armature winding is that as the speed increases the counter EMF naturally reduces the voltage across, and current through the field windings, giving field weakening at high speeds. This means that the motor has no theoretical maximum speed for any particular applied voltage.

 Universal motors can be and are generally run at high speeds, 4000-16000 rpm, and can go over 20,000 rpm.[4] By way of contrast, AC synchronous and squirrel cage induction motors cannot turn a shaft faster than allowed by the power line frequency. In countries with 60 Hz(cycle/Sec) AC supply, this speed is limited to 3600 RPM.[6]

Motor damage may occur from over-speeding (running at a rotational speed in excess of design limits) if the unit is operated with no significant mechanical load. On larger motors, sudden loss of load is to be avoided, and the possibility of such an occurrence is incorporated into the motor's protection and control schemes. In some smaller applications, a fan blade attached to the shaft often acts as an artificial load to limit the motor speed to a safe level, as well as a means to circulate cooling airflow over the armature and field windings. If there were no mechanical limits placed on a universal motor it could theoretically speed out of control in the same way any series-wound DC motor can.[2]



tinman

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #111 on: July 16, 2017, 02:18:45 PM »
Quote
author=lancaIV link=topic=17297.msg508313#msg508313 date=1500206758]
https://en.wikipedia.org/wiki/Universal_motor
.....

Torque-speed characteristics

Series wound electric motors respond to increased load by slowing down; the current increases and the torque rises in proportion to the square of the current since the same current flows in both the armature and the field windings. If the motor is stalled, the current is limited only by the total resistance of the windings and the torque can be very high, and there is a danger of the windings becoming overheated.
The counter-EMF aids the armature resistance to limit the current through the armature.

 When power is first applied to a motor, the armature does not rotate. At that instant, the counter-EMF is zero and the only factor limiting the armature current is the armature resistance.

Usually the armature resistance of a motor is low; therefore the current through the armature would be very large when the power is applied. Therefore the need can arise for an additional resistance in series with the armature to limit the current until the motor rotation can build up the counter-EMF. As the motor rotation builds up, the resistance is gradually cut out.
The speed-torque characteristic is an almost perfectly straight line between the stall torque and the no-load speed. This suits large inertial loads as the speed will drop until the motor slowly starts to rotate and these motors have a very high stalling torque.[5]

As the speed increases, the inductance of the rotor means that the ideal commutating point changes. Small motors typically have fixed commutation. While some larger universal motors have rotatable commutation, this is rare. Instead larger universal motors often have compensation windings in series with the motor, or sometimes inductively coupled, and placed at ninety electrical degrees to the main field axis. These reduce the reactance of the armature, and improve the commutation.[4]

One useful property of having the field windings in series with the armature winding is that as the speed increases the counter EMF naturally reduces the voltage across, and current through the field windings, giving field weakening at high speeds. This means that the motor has no theoretical maximum speed for any particular applied voltage.

 Universal motors can be and are generally run at high speeds, 4000-16000 rpm, and can go over 20,000 rpm.[4] By way of contrast, AC synchronous and squirrel cage induction motors cannot turn a shaft faster than allowed by the power line frequency. In countries with 60 Hz(cycle/Sec) AC supply, this speed is limited to 3600 RPM.[6]

Motor damage may occur from over-speeding (running at a rotational speed in excess of design limits) if the unit is operated with no significant mechanical load. On larger motors, sudden loss of load is to be avoided, and the possibility of such an occurrence is incorporated into the motor's protection and control schemes. In some smaller applications, a fan blade attached to the shaft often acts as an artificial load to limit the motor speed to a safe level, as well as a means to circulate cooling airflow over the armature and field windings. If there were no mechanical limits placed on a universal motor it could theoretically speed out of control in the same way any series-wound DC motor can.[2]


And there you go.


Brad



tinman

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #112 on: July 16, 2017, 03:52:41 PM »
And you seem to think that that is a good thing,,,

Just because we use things in a certain way does not mean that we must,,

So indeed,, there ya go.

WHY??????



The self induced moment is from the inrush of current flow,, the magnetic induced part is the change in flux density the coil sees from the magnetic field,,,,,

Now think this one over,,  change the way you are looking at it,, so if you want it to speed up and maintain its full torque potential you would need to have the full amps passing,, not a reduced quantity of charge,, you and tinman keep on talking about reducing current flow to limit speed, ask yourself why, not how it happens but why would you want to limit the current flow and the torque just to control the speed.

I do not say any such thing.

This is not rocket science,and it seem's that no mater how simply i try to explain myself,your just not getting it.

I have said time and time again-->the more BEMF that can be retained under any mechanical load placed on the motor,the more efficient that motor is.
You seem to be stuck on the fact that the more current you pump into a motor,the more torque that motor will deliver,and you assume the best way to do this,is to remove as much of the BEMF as you can,when in actual fact,the more BEMF the motor can produce,the more torque it will have,while drawing less current from the power supply--so you have things ass about Webby.

Quote
AND if you actually read what was written you would see that if there was no BEMF\CEMF then the motor would run with a constant torque, with a constant amp draw and spin up to oblivion.

Thats not what was said at all.
Quote: If there were no mechanical limits placed on a universal motor it could theoretically speed out of control in the same way.

If there was no BEMF,then the motor would constantly draw the maximum current value allowed by the winding resistance only.
So now,get your self a universal motor,lock the shaft so as it cannot rotate,plug it in,and see how long it last's--this is your motor with no BEMF--a big resistive heater that wouldnt last 1 minute before it smoked up.

Quote
Why would you want to take that approach to reducing\controlling the BEMF\CEMF,, excuse my blunt response but that method is just stupid,, and I am surprised that Brad is not jumping on you a little on this setup,, he knows a little about how it responds.

Yes,that is a little out of the ball park,and not all correct.
But what it will show you,is what happens to the current draw when you remove the self induced EMF(BEMF).

So let me ask you these two questions Webby--and think about them carefully.
we have a motor that is being supplied 10 volts,and has a winding resistance of 1 ohm
1-What would the current draw be from the power supply, if that motor produced the same amount of BEMF as the applied EMF ?
2- What would be the value of the current flowing through the windings?


Brad
2-

citfta

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #113 on: July 16, 2017, 07:23:13 PM »
And you seem to think that that is a good thing,,,

Just because we use things in a certain way does not mean that we must,, AND if you actually read what was written you would see that if there was no BEMF\CEMF then the motor would run with a constant torque, with a constant amp draw and spin up to oblivion.

Your answer is incorrect.  If there is no BEMF,  THERE IS NO TORQUE!


Why would you want to take that approach to reducing\controlling the BEMF\CEMF,, excuse my blunt response but that method is just stupid,, and I am surprised that Brad is not jumping on you a little on this setup,, he knows a little about how it responds.



Well, you got one thing right.  To do that would be stupid.  It was an example to try and get you to understand the relationship between torque and BEMF.  But obviously it failed.  Why would Brad disagree with that?  That is the way motors actually work.  I am sorry you seem to be having such a hard time grasping the concept between torque and BEMF.  But you simply cannot have one without the other.  And I don't understand why you want to have a motor that is simply going to produce a lot of heat and no torque as Brad has already explained to you several times.

lancaIV

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #114 on: July 16, 2017, 08:39:36 PM »
AC 60 Hz : 3600 RPM
AC 50 Hz : 3000 RPM

DC ????? : 3000-3600 RPM
pulsed DC

universal answer ?

how is a variable speed motor commanded ?


citfta

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #116 on: July 16, 2017, 11:20:15 PM »
wrong, and I am trying to get you all to understand that in simple terms.
I did not say that Brad would be in disagreement,, I thought he has tried playing with a universal motor,, perhaps maybe even trying to augment the stator winding with a PM and a few other things.

I am not saying that you do not have one without the other,, I am pointing out what the limiting factor is that needs to be controlled in order to get the motor to produce the same torque at a higher RPM.

So tell me how much torque at the shaft you can have from a motor that is almost stalled compared to the torque from the same motor that is almost at its RPM limit,, where is all the BEMF in the almost stalled motor?

You certainly seem to be confused about how motors operate.  First you are wrong about motors not having the same torque at higher rpm.  As soon as you load the motor the current will increase to provide the torque and return the motor to the speed that produces the BEMF to again balance the applied voltage and torque requirements.  As you load the motor higher the current will again increase to give the torque necessary to keep the speed up.  As has been explained a couple of times already the BEMF acts like a governor to maintain the motor at a given speed based on the design of the motor and the applied voltage.

You are correct that in an almost stalled motor the BEMF is almost none existent.  BUT the agent which causes the BEMF is certainly there and that is the opposing magnetic field either from permanent magnets or energized coils.  If you remove the opposing magnetic field then you will have no torque.  So the same force that gives you the torque is also responsible for giving you the BEMF.

Let me propose another experiment for you.  Get a universal motor and disconnect the field coils from the armature.  Connect a variable power supply to the field coils.  Then connect another variable power supply to the armature brushes.  Now you can see for yourself the effect of varying the field coil current which will affect the torque and BEMF.  If you really want to learn you could also rig a simple prony brake to measure the torque.

Webby, I am perfectly willing to try and help you learn about motors.  But don't keep telling me I am wrong in what I post.  I made my living for over 40 years working on industrial machinery.  I have worked on hundreds of motors and motor controllers.  I have been factory trained on several of them.  If you don't agree with the way motors are being controlled then come up with a better way and you will never have to work again.  Today's motor controllers are very sophisticated devices used in industry for special purposes.  But the normal everyday motor still works on the very same principles I have been trying to get you to understand.

So, once again, the agent or force that gives a motor its torque is the same agent or force that causes BEMF.

Carroll

citfta

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #117 on: July 16, 2017, 11:40:22 PM »
Webby,

Do you know what causes a motor to burn up?  You can burn up a perfectly good motor by overloading it.  How does that happen?  As I explained in the previous post a motor will draw more and more current to meet the torque requirement caused by the load on the motor.  If you overload the motor the motor will draw more current than the wiring of the motor was designed to handle.  Without some form of current protection such as a breaker or fuse the motor will overheat the wiring until the insulation of the wiring breaks down and then the motor shorts out and catches fire.

Another thing you seem confused about is when does a motor have the most torque.  Most AC induction motors actually have more torque when they are up to speed.  That is because the armature rotating at high speed has more current induced into it to create the opposing magnetic field.

DC motors on the other hand, because they have separate field coils that are fully energized from the beginning have starting torque equal to the running torque.  It is kind of amazing to see a large DC motor barely turning and yet moving a massive load.

tinman

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #118 on: July 17, 2017, 01:15:48 AM »
is it me that is not getting what is being said??You keep saying that the weaker the motor the more efficient it is,, you keep heading into the electrostatic motor,, which if you wish to go there I can follow but I do not have a working testbed for that.


I am not assuming the best way is to remove the BEMF,, but rather control it, to USE it,, this is not rocket science after all


or
If the same motor were running at 10,000 RPM making 10N-m of torque or if it were running at 1,000 RPM making 10N-m of torque, which one is making more mechanical power,, it is that simple.


Now ask yourself, what is it that limits the RPM?,,  whatever it is that limits the RPM is what needs to be controlled and used to assist the motor in achieving a higher RPM with the same torque,, it is that simple.


Ask yourself a simple question,,  What is it that is wanted from a motor?
Ask yourself a simple question,,  What is the motor doing?

Quote
If the same motor had a draw of 1A or 10A,, which one would produce more shaft torque Brad,, it is that simple.

Well,it would seem that it is not that simple,as you are once again missing the point,and that point is-why do you want to decrease the BEMF ?
Some here think that by decreasing the BEMF,you make the motor more efficient-which,as i have stated right through this thread-you do not.

To answer your question-torque is not power.
The motor that is drawing only 1 amp,will do more useful mechanical work for a given electrical input value than that of the same motor drawing 10 amp's--it's that simple.
Reason being,the motor drawing 10 amp's will be dissipating a larger percentage of the input power as heat to that of the motor that is drawing only 1 amp.

So,the motor drawing only 1 amp converts more of the electrical input energy into mechanical energy than that of the motor drawing 10 amp's.

So,there is your answer--higher the BEMF,the more efficiently the motor converts electrical energy into mechanical energy.


Brad

tinman

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Re: Where the OVERUNITY using INDUCTION COILS comes from (eg Joule Thief)
« Reply #119 on: July 17, 2017, 03:55:02 AM »
I see that the point and methodology I am trying to get across is not making the trip,, so be it.

I  understand the working principles and am even comfortable with a lot of the math that goes along with it,, I am not confused nor am I missing it.

BEMF is the built in *limiter* for RPM,,

Edited before posting,, since it does not matter, apparently, anyway.

Well-what is your point Webby?
Why would you want to eliminate BEMF?


Brad