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The reason is that internal voids within the insulation will discharge as the voltage rises; once discharged, they will not do so again at some higher voltage. if all voids become discharged, theoretically the plot of tan delta versus voltage would level off to a horizontal line. In effect, tip-up becomes "negative".
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Theory for brake test on three phase induction motor?
why three phase induction motor is delta connected
What is easier to measure volts amps or watt?
If you have the right test equipment amps are the easiest to measure. A slip over the wire amp meter is easier to use than a clamp on amp meter. The other two values have to be measured by using test leads from the test equipment.
What is TAN DELTA testing of transformer?
Tan Delta is also known as the 'loss angle' or 'dissipation factor'. It is used to test the level of degradation in insulation materials of electrical machines and power cables. The winding insulation of an electrical machine, or a cable free from defects, will act as a perfect capacitor, that is, it will only store energy and not dissipate it. In an ideal capacitor, the voltage and current are out of phase by 90 degrees and the current flowing through the insulation is purely capacitive Ic. However, dielectric losses within the insulation due to deterioration or other factors, will result in the reduction of the resistance in the insulation. This will in turn increase the resistive current Ir. The phase angle between the current and voltage is now less than 90 degrees, and the extent to which this is less than 90 degrees gives the level of degradation in the insulation. So this 'loss angle' is required to be measured. If the angle is Delta, then the tangent of Delta can be calculated by dividing is 'opposite over adjacent', which is Ir/Ic. There are various methods of how this is tested and industrial standards, such as the IEC provide acceptable values of Tan-delta for different types of insulation.
How do you measure IGBT?
Digital multi-meter (DMM) test procedure:Equipment Requirement - DMM with diode check mode and battery voltage less than 20V. (Typical units using 9V battery are OK).Collector-Emitter Junction test: With the module out of circuit remove the conductive foam and short the gate to emitter.With DMM in diode check mode, the collector to emitter should give a normal diode reading with positive on the emitter and negative on the collector.The DMM should read open or infinite with positive on the collector and negative on the emitter. Damaged IGBTs may test as shorted in both positive and negative directions, open in both directions, or resistive in both directions.Gate Oxide test: With the DMM in resistance mode the resistance from gate to collector and gate to emitter should read infinite on a good device. A damaged device may be shorted or have resistive leakage from gate to collector and/or emitter.
Why is it required to vary the field current in only one direction while performing the open circuit test on dc generator?
rectification to the negative voltage
Which aldehyde do not give fhelings test?
All aldehydes give a positive result with Fehling's test. All ketones give negative results.
What is acceptable value of tan delta in oil filled and dry type 33 KV transformers?
Tan Delta is a condition monitoring test. Value of Tan Delta very much depends upon the temperature and recommended values at 20Deg.C is 1. Values at other temperatures can be determined by using correction factor given in IEC76
Negative pregnancy test but urinated on it again and it went positive?
This happened to me when I got pregnant with my third child. The first test was negative and the second positive. From what I understand, a pregnancy test can give a false negative but rarely gives a false positive.
Can gallstones give you a false negative pregnancy test?
The gallbladder has no effect on hormones of pregnancy. Gallstones will not affect a pregnancy test.
Can a pregnancy test give a false negative if you don't pee on the stick long enough?
YES! Every pregnancy test is different and if the instructions are not followed 100% then there is a chance you could read a false negative. I suggest taking another test and if that dos not give you a conclusive answer or you are still unsure if the test is correct, consult your doctor for a blood test.
Do blueberries give off a negative urine test?
No, blueberries shouldn't have an effect on these tests.
Why phenylalanine give negative result with xanthoproteic test?
Phenylalanine gave a yellow to orange color in xanthoproteic test which means it is positive.
Can Advil give you a false negative pregnancy test?
yes i think it could just wait for the medicine to wear of and take another test ... :/
What pain medications can give a false negative on a pregnancy test?
Pain medication will not cause a pregnancy test to be falsely negative, using the test too soon can cause a false negative. Wait 3 or 4 days, if your period doesn't come take the test again, make sure you are following all directions precisely.
Can an expired pregnancy test give a false negative reading Even if it's only 1 year expired?
Yes it can. Any pregnancy test can give a false negative (not picking up on the presence of the hormone hCG (human Chorionic Gonadotropin)) however they will not give a false positive (The hormone will only be there if you are pregnant) An expired pregnancy test will be even less accurate.
What are the results of a catalase test on Lactococcus lactis?
E.coli shows positive result for catalase test..staphylococcus aureus and serratia marcescens too..pseudomonas and klebsiella does not give any vigorous bubbling therefore, it shows negative result
How starch can give a negative iodine test?
Starch can give a negative iodine test when starch is mixed with iodine in water. The iodine gets stuck in the coils of beta amylase molecules and the starch forces the iodine atoms into a linear arrangement in the central groove of the coil.
