Understand Three Phase Motor

An overview of three phase motor

Jessie Stobo Watson Webb (31 July 1880 17 February 1944) was an Australian academic and historian, one of the first female teachers at the University of Melbourne. The only monograph of Webb's life is by R. T. Ridley, published by the History Department of Melbourne University.

Death of three phase motor

During her last stint as acting professor, Webb continued to exercise her administrative duties in running the history department despite being hospitalised with cancer. Webb died at the Linden Private Hospital in St Kilda in 1944. Following her death, the library in the history department at the University was named after her. Webb bequeathed 7128 to the University in her will, which is used to fund the Jessie Webb Scholarship, which provides funding for a student to emulate Webb's own experience at the British School, to study and research for a season in Greece.

Trinity College of three phase motor

From 1901 to 1912 Webb tutored history and political economy at Trinity College at the University of Melbourne; during this time she also tutored at Ormond College and at several girls' secondary schools. Webb also operated an independent coaching college, staffed with other female university graduates, who ran tutoring programs catering for students from matriculation level through the whole duration of undergraduate courses. In May 1906 she registered with the government as a teacher.

Night lecturerIn December 1908, after her third application to the University, Webb was employed as a night lecturer with the history department the first woman to be appointed to such a position in Australia teaching ancient and British history. At her appointment, Webb was the only other teacher in the department, aside from Professor John Simeon Elkington.

Full-time lecturerOn Elkington's retirement in 1913, she was elevated to a full-time lecturer, after Ernest Scott, the new professor, successfully lobbied the University to provide for a full-time assistant. Under Scott, and later under Scott's successor, Max Crawford, Webb served as acting professor whenever the professor himself was on leave, taking over their classes and their administrative duties too. Webb had extensive teaching responsibilities of her own; in 1914, for example, she gave two lectures each week in Ancient History, and two further evening lectures in both Ancient History and British History Part I weekly, in addition to a tutorial class with the honours students and consultations on the students' work. Webb was primarily responsible for communicating with the correspondence students, and she even "sent her own books out on rotation to these students as the university provided no funding to buy books for circulation." Webb did not underestimate the importance of those students, comprising as they did about a quarter of the faculty's enrolment in 1913, "and she knew that many of them were teachers trying to improve their qualifications."

Webb was promoted to become a senior lecturer within the history department in 1923; in 1925 she was an acting professor. Webb was an acting professor again in 193334 and in 194244. However, despite Max Crawford recommending Webb for an associate professorship in his 1937 report to the University, Webb was never permanently promoted beyond the position of lecturer, only ever acting as a fill-in. Her friend Dr Sweet had been appointed to an associate professorship in 1919, the first female to hold such a position at the University, though only after being passed over in the search for a full professor to succeed Baldwin Spencer, despite extensive support and recommendation from within the local and international academic community. Discrimination against women in academia was not uncommon at the time. In a speech to the University's Historical Society in 1928, reported in Farrago, Webb spoke sardonically of the systematic exclusion of women from the archaeological profession. Webb's friend Ella Latham could no longer continue in her own teaching career after her marriage. Indeed, Webb herself was only employed by the University on her third application, having been beaten twice prior by male candidates with, on paper, lesser qualifications than she. Webb remained the only female employee in the history department until the appointment of Kathleen Fitzpatrick in 1938.

Beginning in 1924, Webb organised regular purchases on behalf of the University of ancient coins and statuary casts, for the purposes of study and to decorate the Arts faculty building. The Jessie Webb Collection now forms part of the Classics and Archaeology Collection at the Ian Potter Museum of Art. Elsewhere in university life, Webb contributed to the founding of the University Women's College since 1975 known as University College which was established in 1933.

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Steps in Rewinding Three Phase Motor?
Step 1 - remove stator from motor housing. - generally done with a 'gas circle' this is a ring with about 8 - 10 gas burners. It will expand the steel casing and let the stator drop out. Step 2 - remove burnt copper windings, usually done by sawing one end off, then pulling it out of the slots from hte other end. This will generally pull the insulating materials out with it. Step 3 - insert new insulators in the slots. Step 4 - divide the number of slots into 3, starting at the desired slot start feeding in the new copper coils in one end out the other and so forth, making sure that each time it is going into the correct division of 3 slots to keep the magnetic syncronisation correct. Step 5 - once all the coils are completed dip the motor into the curing solution to fully insulate the coils ( see my other answer for heat ratings ) Step 6 - re install into stator housing with the gas circle and rebuild.( Take care to use new bearings on the motor shaft as the old ones will be full of carbon. Interesting fact for you, if you apply voltage to the stator when it is removed and put a ball bearing in it you will be able to find the spot where the coil has failed, bearing will go round in the stator with the magnetism and drop when it comes to the open link. This is done when a motor continuously fails and the phase recognition needs to be carried out to ensure there is no fault with the power being supplied to the motor. Hope this helps.1. Electric Power comes back when I open up warm tap water and then goes when I close the tapAs already said by other authors, the interrupted phase is supplied by one or both of the other 2 phases when the water heater switches on (backfeed). It could be a also multiple problem with a combination of shortcut(s) and low resistances between phases or phase to Neutral. This could increase the voltage to a level thatdestroys the devices that are fed by this backfeed via the water heater, since the water heater's resistances are very low and the sum of 2 phases with 120 degree difference could be fed back. The heater is connected to a 3-phase breaker that can only interrupt 3 phases alltogether, even if there is an overload on 1 phase only. That breaker apparently did not trip - or the heater does not have a combined triple circuit breaker, but only 3 separate ones, which is against the standard/code.Most likely an upstream fuse or breaker did trip, which is separate for all 3 phases. Do neighbours report problems with some electric circuits not working? If not, the problem is within the own house/apartment.The heavy main fuses/breakers upstream of the water heater directly at the incomer box of the supplier should give the downstream breakers the priority, i.e. a short in the wiring of the water heater should cause the downstream breaker(s) to trip, and not the main fuse/breaker. Another 3 main fuses or breakers (for each phase) normally sits upstream close to the meter, and one of those could also have tripped.2. How much energy does it take to change water from the solid phase to liquid phase?A calorie is a unit of heat equal to the amount of heat required to raise the temperature of one kilogram of water by one degree at one atmosphere pressure 1 calorie = 4.18400 joules3. Finding phase velocity for froude number scalingI am not sure where did you brought the would eep water relationship' in here. If you are dealing with usual water wave (gravity, surface, linear, and close to sinusoidal wave form), then the relationship you would need to use will be dispersion relationship.$omega^2 = gktanh(kh)$As you are assuming deep water, it becomes: $omega^2 = gk$Which leads to almost exactly same equation you came up with, but one less power of T:$lambda = dfracgT^22pi = 72m$and phase velocity of 10.61 meter/second.(Actually, your original calculation, with $T^3$ was incorrect. That should have give you wave length of 491 meter, instead of 712 meter)Additional comments:
How to Run a Three Phase Motor Always in One Direction Even If Three Phase Are Changed by Mistake ?
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