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we must not get confused and think very simply that soft-start and variable frequency drive have the same role. AC drives are more expensive and soft starters are not able to regulate frequency. There are many other considerations before deciding if a variable frequency drive or soft -start is needed for your load.
The question is about we have an unbalanced system under study and i found that power factor calculation does not obeys the well known geometrical relationship called power triangle nor the arithmetical relationship also.
However if I consider that reactive power is only an effect of the phase shift between the voltage and current the calculated power factor is almost the power factor measured.
Efficiency is built into a motor on design and on the quality of the steel that makes up the laminated core. The fan and bearings are also a factor. "T" frame motors have quite a heavy slot fill so there is not much you can do with conductor size. There is not a lot you can do with bearings because the housings and journals are manufactured for a specific bearing series and size. You could put a smaller fan but the motor would overheat. In a rewind situation you have to be extremely careful to maintain the efficiency.
Due to power electronics technology and microelectronics technology rapid development, variable frequency drive reforms and upgrades speed also is faster, introduce new products, improve performance continuously, enrich and strengthen function constantly. China domestic market has lots of variable frequency drive brands, such as Danfoss, ABB, Gozuk, SIEMENS, GE, Schneider, etc.
Power factor is actually the factor of generated power utilized in performing useful work. Ideally it is equal to 1, but practically it is always less than 1 as current always take time to reach at lower potential points. The good example to understand this phenomenon is the traveling of air towards low pressure areas. Air always travels towards low pressure area but it can never reach at low pressure area in 0 seconds.
I was recently trying to connect my Delta VFD E series drive with my laptop using Vfd-Soft software (which I downloaded from Delta website) and RJ 45 to USB converter(RS232/RS485 converter). I connected the variable frequency drive to supply and connected the connecting lead to drive and pc both.
The Tan-Delta test is an off-line AC test, usually sinusoidal. The Tan Delta is the ratio of the real (resistive) current to the capacitive current. This ratio should be relatively constant despite test voltage making the Tan Delta value a pass/fail. The resistive current is typically much smaller than the capacitive current on a good insulation system.
Surge and hipot testing can be potentially destructive. But, so can a Megger test on a motor which is in very poor condition. When testing a motor, tests are performed starting with the low voltage tests and moving on to the higher voltage tests. When a motor fails any test, the more rigorous tests are not performed, so no further damage is done. If a motor fails a resistance test or a Megger test, you do not perform the hipot and surge tests.
Motor Circuit Analysis (MCA) is a de-energized test method and the test can be initiated from the Motor Control Center (MCC) or directly at the motor. The advantage to testing from the MCC is the entire motor system, including the connections and cables between the test point and the motor, is evaluated.
For cable lengths up to 100 meters (and motor suitable for inverter applications) it is not necessary a filter; for lengths from 100 to 200 meters, a series reactance can be used; for greater lengths it is necessary an LC filter at inverter terminals. The limit lengths can be different from different manufacturers and voltage levels (LV/MV).
Noise and sound are a bit tricky to deal with. Generally the noise from the motor fan is "white noise" and not objectionable to the ear, except for large machines that were mentioned or as mentioned below. The objectionable noise normally comes from the slot combination used in the design. The slot combination generates a variety of frequencies, many of which can be easily calculated based on the number of slots, various combinations, slip, speed, frequency of operation, etc.
I have been in the electric motor repair industry all my working life, (50 years) and I have watched this industry progress. During my apprenticeship in the UK we were taught all about the damages that can be done to a stator core if proper procedures were not followed and in all honesty when I first arrived on Canadian shores I was horrified at some of the methods.
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service The engineers in AC Drive China are very professional in Chinese automation industrial control fields, provide you comprehensive energy saving solutions.

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