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http://answers.yahoo.com/question/index?qid=20110630015105AAuZR0yCan power factor of an electrical system be measured as a negative value?A negative power factor would indicate that current leads or lags the voltage by more than 90 degrees. Physically, that can happen if the load is returning power to the source rather than using power. For example, if an induction motor is used to operate an electric railway locomotive, the power factor will be lagging by less than 90 degrees as the locomotive climbs a hill. If the motor is nearly loaded, the power factor might be about 0.85. If the track is level at the top of the hill, the motor's load will be reduced and the power factor might drop to 0.65. As the locomotive begin to go downhill, the power factor drops more and may be come negative as the motor begins to operate as a generator returning braking power to the source.Source(s):I have worked as an engineer in the manufacture of variable frequency drives (VFD). We tested drives under load by using the VFD under test to control an induction motor which drove a second induction motor that was connected to utility (mains) power. Using the VFD to slightly overspeed the second motor forced that motor to become a generator and return power to the utility. Another Answer: The power factor itself, will be positive, between 0 and 1, and is given from cos (theta). If it is 1, your load is purely resistive. If it is 0, your load is purely reactive. The angle theta, however, could be negative or positive. If it's negative, then the reactive portion is capacitive, and your voltage is lagging behind the current. If it's positive, then the reactive portion is inductive, and voltage is leading current.
There are several different definitions of power in AC circuits; all, however, have dimension of V*A or W (watts). 1. Instantaneous power: [/i] p(t) is the time function of the power, p(t) = u(t)*i(t). It is the product of the time functions of the voltage and current. This definition of instantaneous power is valid for signals of any waveform. The unit for instantaneous power [/i]is VA. 2. Complex power: [/i] S [/font] (http://www.tina.com/English/tina/course/29power/power.1.gif) Complex power is the product of the complex effective voltage and the complex effective conjugate current. In our notation here, the conjugate is indicated by an asterisk (*).Complex power can also be computed using the peak values of the complex voltage and current, but then the result must be divided by 2. Note that complex power is applicable only to circuits with sinusoidal excitation because complex effective or peak values exist and are defined only for sinusoidal signals. The unit for complex power [/i]is VA. [/font]3. Real [/i]or average power[/i]: P can be defined in two ways: as the real part of the complex power or as the simple average of the instantaneous power.[/i] The second definition is more general because with it we can define the instantaneous power [/i]for any signal waveform, not just for sinusoids. It is given explicitly in the following expression (http://www.tina.com/English/tina/course/29power/power.2.gif) The unit for real[/i] or average power[/i] is watts (W), just as for power in DC circuits. Real power is dissipated as heat in resistances. 4. Reactive power: [/i]Q is the imaginary part of the complex power. It is given in units of volt-amperes reactive[/i] (VAR). Reactive power is positive[/i] in an inductive[/i] circuit[/i] and negative[/i] in a capacitive circuit[/i]. This power is defined only for sinusoidal excitation. The reactive power doesn't do any useful work or heat and it is the power returned to the source by the reactive components (inductors, capacitors) of the circuit [/font] 5. Apparent power: [/i]S is the product of the rms values of the voltage and the current, S = U*I. The unit of apparent power is VA. The apparent power[/i] is the absolute value of the complex power[/i], so it is defined only for sinusoidal excitation.[/font]
*** As I mentioned, I do indication experiments. The top universities will have the DSO and experts to do the real experiments. That is why we need them.
*** Use a wire to directly connect the two ends of the capacitor for 5 minutes. Put it back on the JT circuit and the LED should show no light. Check the Output voltage waveform on the Atten Oscilloscope. It should show NO more characteristic pulsing waveform.
Mark Dansie and team visited G-LED USA and were impressed. They saw the FLEET without battery lighting during the entire meeting. They also saw the 2KW unit lighting 2,500 LEDs.Their plan is to fly to Hong Kong to meet me and the owners of BSI. They wanted to purchase a number of Lead-out Energy Research kits for testing now and may go into business arrangement afterwards.Apparently, they have much better equipped laboratories and can do the 4 channel, maths function tests. My indication experiments will be improved to a much higher degree of accuracy.The owners of G-LED and BSI will also meet shortly to decide on the marketing strategy. Hopefully, that will happen before Christmas.The Divine Wine will be tasted by many this Christmas.
That is a very interesting way of measuring the input/output. So with the Cap we would have a definite buffer of input energy while the output we measure with the scope.Quick question, would not the dropping voltage of the cap as we use it in the JT change the whole behavior of the JT and therefore its performance?
I had the impression that JT needs a stable input power to perform to its peak performance, no?Great tip.Fausto.
Yes, Lawrence, there is. But first you must realize that POWER is not the conserved quantity of interest when making excess ENERGY claims of overunity or COP>1..............
If we have two 2 channel oscilloscopes, can we use one to measure the Input Power and one to measure the Output Power at the same time? We can easily calculate the average power values. Will that be a legit comparison?
Yes and no. In the first place you are not concerned with POWER, but energy. Please try to remember that. The instantaneous power curve is the intermediate step to obtaining energy flow values, and it is the energy that is important.
Thank you for the very informative answer. I am lucky to have two Atten oscilloscopes. On another point, some universities have the 4 channel high end DSOs. Will that make the measurement easier and more accurate?
Facepalm.Will you please go back and read my previous posts? There is a difference between precision and accuracy. Using the high end 4 channel scope with live math and integration will make your measurements easier and more PRECISE. Not necessarily more accurate. And in this case, accuracy is much more important than another decimal place or two of precision.Consider the archer. She fires her arrows at a big target with a tiny red center bullseye. She tries her best to hit the bullseye dead center (accuracy). She strives to do this with every arrow she fires with very small error (precision).So she fires off some arrows, and all four of them are in a tight cluster, only a millimeter space between them. This is PRECISION.But... alas, the cluster is way down and to the left of the aim point, the bullseye. This is a lack of ACCURACY.So she adjusts the sight of her bow, she trims the fletching of her arrows and fires off four more arrows. This time they are in a looser group, they are further apart. She has lost some PRECISION.But.... look, one of the arrows is dead center on the red bullseye and the rest are clustered just a few millimeters away. She has achieved much greater ACCURACY, even though her precision is less than before.Which would you rather achieve, better Precision, or better Accuracy?