Brad said:
So the stepper motor output is acting like a near pure current source. The only way I can think this can happen is if due to the nature of the construction of the stepper motor, i.e. it reaches a limit in magnetic energy transferred per pole of rotation due to a shunting effect.
It may be useful to investigate this more fully. Perhaps Smudge has a much better explanation.
It dose seem to act in an odd way.
But first a question-->and this may sound silly,but
When measuring AC current and voltage,how do we know which way-or,from what device(source) the bulk of the power is coming from?.
To make my question more clear,lets say we have two black boxes,and we have a common or neutral wire from one box to another,and a live (or hot) wire with a 1 ohm CVR in series on the hot wire to measure the current flowing from one to the other black box. Lets assume that it's an AC current flow. So we place one channel of our scope across the neutral/common and live wires to measure voltage. We then place the second channel of the scope across the CVR to measure current. Without knowing which black box is the power source,and which is the sink,how do we know which way the power is flowing ?.
There is a reason for this question.
Below is a schematic of two circuits-along with scope shots.
The first circuit you will see a VR (which is 200 ohm's-forgot to put that value in the schematic),a 1 ohm CVR,and the stepper motor,which is being used as our generator.
The first 4 scope shots show the various resistance settings on the VR(which is our load on the generator), and the associated voltage and current traces in the scope shot for the stated resistance value of the load.
You will see that the maximum current the stepper motor can produce is 76mA.
The last scope shot shows the values taken when the second circuit is use,and that is just replacing the resistive load with the 240v mains LED bulb. I have no idea as to what the circuit inside is,as i cannot get it apart without breaking it--it is not as simple as the CFLs to get apart.
So if the maximum current that the stepper motor can produce is 76mA,then how is it that it can now produce over 270mA of current when the LED bulb is used as the load. We also now have 256 volts across the LED,but as you can see,the phase relationship between voltage and current is near 90* out close to 80* i would say.
But my question is--when using the LED as the load,how do we know that the bulk of the power is flowing from the stepper motor to the LED,and not from the LED to the stepper motor,as the stepper motor just will not produce this kind of current-regardless of RPM. Even with a dead short across the stepper motor outputs,there is no reflection seen on the prime mover(as seen in other video's)and no increase of current above that 76mA.
The other thing is,there is suppose to be over 250 volts AC across that LED,and it dose light very bright-->but i can hold the bare wires in my hands while the LED is shining brightly,and i get hardly any sort of a tingle at all
What kind of electricity is this
Brad
Never let your schooling get in the way of your education.
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Topic: Eddy Current Heating (Read 15831 times)
