Summary index post for the “One Question per Day” section in the Electrical Technology Discussion Forum (restarted on November 3, 2010)

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This post was last edited by zhaohh3211 on 2010-12-8 15:35. Summary post of “One Question per Day” in the Electrical Technology Discussion Forum. 1. [One Question per Day 20081227] What is the role of a DC system in substations? http://bbs.hcbbs.com/thread-359012-1-2.html 2. 【Daily Question 20081229】What effects can improper setting of the quiescent operating point have on the operation of an amplifier in an amplification circuit? ://bbs.hcbbs.com/thread-359784-1-2.html 3. 【Daily Question 20081230】Why is high-voltage power transmission used? http://bbs.hcbbs.com/thread-360620-1-1.html 4. 【Daily Question 20081231】What are the causes of short circuits? What are the hazards? Can short circuits be utilized in production? tp://bbs.hcbbs.com/thread-361477-1-1.html January 5, 【Daily Question 20090101】Can a 50HZ power transformer be used satisfactorily in foreign 60HZ power grids? http://bbs.hcbbs.com/thread-362326-1-1.html 6, 【Daily Question 20090102】If the neutral point of a motor’s three-phase windings comes into contact with the ground, will the leakage circuit breaker trip? http://bbs.hcbbs.com/viewthread.php?tid=362921&extra=page%3D1&frombbs=1 7, 【Daily Question 20090103】How can one roughly determine the fault condition in a circuit based on the behavior of fuses when they blow? http://bbs.hcbbs.com/thread-363707-1-1.html 8, 【Daily Question 20090104】What parameters should be given priority when selecting thyristor components? http://bbs.hcbbs.com/viewthread.php?tid=364250&page=1&extra=page%3D1 9, 【Daily Question 20090105】When a motor is in operation and its bearing temperature is too high, what aspects should be considered to find the cause? http://bbs.hcbbs.com/thread-365125-1-1.html 10, 【Daily Question 20090106】Why must the neutral line N in a UPS be grounded repeatedly? http://bbs.hcbbs.com/thread-366004-1-1.html 11. 【Daily Question 20090107】What are the main differences between synchronous motors and asynchronous motors? http://bbs.hcbbs.com/thread-367126-1-1.html 12. 【Daily Question 20090108】How is excitation achieved in synchronous motors? Can changing the polarity of the excitation voltage change the direction of rotation of the motor? http://bbs.hcbbs.com/thread-368210-1-1.html 13. [Daily Question 20090109] How to connect cable cores with different cross-sections and made of different metals? http://bbs.hcbbs.com/viewthread.php?tid=368991&page=1&extra=page%3D1 14. [Daily Question 20090110] What are the causes of significant imbalance in the no-load current of asynchronous motors? http://bbs.hcbbs.com/thread-369518-1-1.html 15. [Daily Question 20090111] What is the function of a knife switch in power operation and maintenance? http://bbs.hcbbs.com/thread-370159-1-1.html 16. [Daily Question 20090112] What is the function of transformer oil? http://bbs.hcbbs.com/thread-370683-1-1.html 17. 【Daily Question 20090113】 What is the function of the gas relay in an oil-immersed transformer? http://bbs.hcbbs.com/thread-371505-1-1.html 18. 【Daily Question 20090114】What is the function of the polarizing switch in a transformer? http://bbs.hcbbs.com/viewthread.php?tid=372226&page=1&extra=page%3D1 19、【Daily Question 20090115】How should the neutral wire of a transformer be handled? http://bbs.hcbbs.com/viewthread.php?tid=373019&page=1&extra=page%3D1 20. 【Daily Question 20090116】What are the protections for transformers? http://bbs.hcbbs.com/thread-373804-1-1.html 21. 【Daily Question 20090117】What are the commonly used special transformers? ttp://bbs.hcbbs.com/viewthread.php?tid=374637&page=1&extra=page%3D1 22、【Daily Question 20090118】What is the function of the oil collection tank in an oil-immersed transformer? http://bbs.hcbbs.com/thread-375117-1-1.html 23. 【Daily Question 20090119】What are the conditions for parallel operation of power transformers? http://bbs.hcbbs.com/thread-375491-1-1.html 24. 【Daily Question 20090120】How are the temperature and temperature rise of oil-immersed power transformers specified? http://bbs.hcbbs.com/viewthread.php?tid=376126&; 25. 【Daily Question 20090121】What is the difference between 4P and 3P circuit breakers? http://bbs.hcbbs.com/viewthread.php?tid=376872&page=1&extra=page%3D1 26. 【Daily Question 20090122】Why do some soft starters require the starter to be bypassed after starting a motor, while others do not? http://bbs.hcbbs.com/viewthread.php?tid=377268&extra=page%3D1&frombbs=1 27. [Daily Question 20090123] What are the two control variables for soft start? http://bbs.hcbbs.com/viewthread.php?tid=378051&; 28. [Daily Question 20090124] What are the advantages and disadvantages of soft start compared to autotransformer starting? http://bbs.hcbbs.com/thread-378286-1-1.html 29. [Daily Question 20090125] What should be done if a motor cannot start when using soft start for current limiting during startup? http://bbs.hcbbs.com/viewthread.php?tid=378595&; 30. [Daily Question 20090126] How should the startup interval be handled when using a soft starter to control motors that start frequently? http://bbs.hcbbs.com/viewthread.php?tid=378835&; 31. [Daily Question 20090127] What are the reasons for the circuit breaker to trip when using a soft starter to start a motor? http://bbs.hcbbs.com/thread-379048-1-1.html 32. 【Daily Question 20090128】Why cannot a current transformer operate with an open circuit? http://bbs.hcbbs.com/viewthread.php?tid=379288&extra=page%3D1&frombbs=1 33、【Daily Question 20090129】What is the function of a high-voltage load switch? http://bbs.hcbbs.com/thread-379443-1-1.html 34. 【Daily Question 20090131】What is the difference between a high-voltage load switch and a disconnect switch? http://bbs.hcbbs.com/thread-379905-1-1.html February 35, 【Daily Question 20090202】What issues should be taken into account when using self-core transformers for temporary construction purposes? http://bbs.hcbbs.com/viewthread.php?tid=380597&page=1&extra=page%3D1 36、【Daily Question 20090203】Can an autotransformer be used as a transformer for safety lights? http://bbs.hcbbs.com/thread-381286-1-1.html 37、【Daily Question 20090204】What is the difference between an autotransformer-type voltage regulator and a tube-based voltage regulator? http://bbs.hcbbs.com/viewthread.php?tid=382624&extra=page%3D1&frombbs=1 38、【Daily Question 20090205】Does a welding machine belong to an autotransformer? What is the principle of voltage regulation? http://bbs.hcbbs.com/thread-382829-1-1.html 39. [Daily Question 20090206] What is the term for a rapid decrease in voltage in an AC welding machine? http://bbs.hcbbs.com/viewthread.php?tid=383602&; 40. [Daily Question 20090207] What does the concept of “two tickets and three systems” refer to in electrical work? http://bbs.hcbbs.com/thread-384345-1-1.html 41. [Daily Question 20090210] What are the technical measures used in electrical work? http://bbs.hcbbs.com/viewthread.php?tid=386321&; 42. [Daily Question 20090211] Are flameproof electrical devices also waterproof? http://bbs.hcbbs.com/thread-386873-1-1.html 43. [Daily Question 20090212] Into which categories can explosion-proof electrical devices be divided? http://bbs.hcbbs.com/viewthread.php?tid=388431&; 44. [Daily Question 20090213] What is the role of torque boost in the parameter settings of an inverter? http://bbs.hcbbs.com/thread-388450-1-1.html 45. [Daily Question 20090214] Can the power cable and motor cable of an inverter be swapped? http://bbs.hcbbs.com/viewthread.php?tid=389210&extra=page%3D1&frombbs=1 46. [Daily Question 20090215] Why is it necessary to install a reactor when using an inverter? http://bbs.hcbbs.com/viewthread.php?tid=389843&; 47. [Daily Question 20090216] At what length of output motor cable should an output reactor be installed in an inverter? http://bbs.hcbbs.com/viewthread.php?tid=390522&extra=page%3D1&frombbs=1 48. [Daily Question 20090217] What is the difference between an inverter and a soft starter? http://bbs.hcbbs.com/viewthread.php?tid=391406&; 49. [Daily Question 20090218] What is the purpose of adjusting the U/F curve of an inverter? http://bbs.hcbbs.com/thread-392264-1-1.html 50. [Daily Question 20090219] What are the requirements for the installation environment of an inverter? http://bbs.hcbbs.com/viewthread.php?tid=393224&; 51. [Daily Question 20090220] What is the difference between an AC-AC inverter and an AC-DC-AC inverter? http://bbs.hcbbs.com/viewthread.php?tid=394168&extra=page%3D1&frombbs=1 52. [Daily Question 20090221] Why can an inverter improve the power factor? http://bbs.hcbbs.com/viewthread.php?tid=395432&extra=page%3D1&frombbs=1 53. [Daily Question 20090222] In which types of equipment is it more energy-efficient to use an inverter? And why? http://bbs.hcbbs.com/viewthread.php?tid=396152&extra=page%3D1&frombbs=1 54. [Daily Question 20090223] Some inverters have a resistor box connected to them externally; what is its purpose? http://bbs.hcbbs.com/thread-396563-1-1.html 55. [Daily Question 20090224] How much power does an inverter consume itself? http://bbs.hcbbs.com/viewthread.php?tid=397553&extra=page%3D1&frombbs=1 56、【Daily Question 20090225】In what aspects does the power consumption of inverters themselves manifest itself? http://bbs.hcbbs.com/viewthread.php?tid=398663&extra=page%3D1&frombbs=1 57、【Daily Question 20090226】Is it acceptable to wire the inverter in this way? http://bbs.hcbbs.com/thread-399897-1-1.html 58. [Daily Question 20090227] Is it feasible to wire the inverter in this way (Part 2)? http://bbs.hcbbs.com/viewthread.php?tid=400824&extra=page%3D1&frombbs=1 March 59、【Daily Question 20090302】Is there a subsidy for using energy-saving lamps? http://bbs.hcbbs.com/thread-403337-1-1.html 60. 【Daily Question 20090303】Three-phase leakage protectors: Do they trip when the currents of the three-phase motors connected to them are unbalanced? http://bbs.hcbbs.com/viewthread.php?tid=404438&extra=page%3D1&frombbs=1 61、【Daily Question 20090304】Is it possible to adjust the phase of an inverter? http://bbs.hcbbs.com/thread-405462-1-1.html 62. [Daily Question 20090305] Time adjustment of the frequency converter? http://bbs.hcbbs.com/viewthread.php?tid=406511&extra=page%3D1&frombbs=1 63. [Daily Question 20090306] Parameter setting of the frequency converter? http://bbs.hcbbs.com/thread-407948-1-2.html 64. [Daily Question 20090308] Parameter setting of the frequency converter (II)? http://bbs.hcbbs.com/thread-409334-1-1.html 65. [Daily Question 20090309] Parameter setting of the frequency converter (III)? http://bbs.hcbbs.com/thread-410200-1-1.html 66. [Daily Question 20090310] Parameter setting of the frequency converter (IV) http://bbs.hcbbs.com/thread-410626-1-1.html 67. [Daily Question 20090311] Parameter setting of the frequency converter (V)? http://bbs.hcbbs.com/thread-411800-1-1.html 68. [Daily Question 20090312] Parameter setting of the frequency converter (VI)? http://bbs.hcbbs.com/thread-412726-1-1.html 69. [Daily Question 20090313] Parameter setting of the frequency converter (VII)? http://bbs.hcbbs.com/thread-414094-1-1.html 70. [Daily Question 20090314] Parameter setting of the frequency converter (VIII)? http://bbs.hcbbs.com/thread-415033-1-1.html 71. [Daily Question 20090315] Parameter setting of the frequency converter (IX)? http://bbs.hcbbs.com/thread-416089-1-1.html 72. Why does a frequency converter need to change voltage as well as frequency? http://bbs.hcbbs.com/thread-416578-1-1.html 73. 【Daily Question 20090317】How many are the basic methods for checking electrical equipment? http://bbs.hcbbs.com/viewthread.php?tid=418166&highlight 74、【Daily Question 20090318】What are the general principles for selecting automatic air switches? http://bbs.hcbbs.com/viewthread.php?tid=418926&highlight 75、【Daily Question 20090319】What is the power factor? What is the significance of improving the load power factor? http://bbs.hcbbs.com/viewthread.php?tid=420821&highlight 76、【Daily Question 20090320】What is the main purpose of the AC withstanding voltage test for electrical equipment? http://bbs.hcbbs.com/viewthread.php?tid=419922&page=1&extra 77、【Daily Question 20090322】What are the reasons for the heating of the contacts of an isolating switch? http://bbs.hcbbs.com/viewthread.php?tid=422380&highlight 78、【Daily Question 20090323】Why cannot a DC motor be started directly? http://bbs.hcbbs.com/viewthread.php?tid=423009&highlight 79、【Daily Question 20090324】If you find someone has been electrocuted, please explain in detail how to provide first aid http://bbs.hcbbs.com/viewthread.php?tid=424047&highlight 80、【Daily Question 20090325】What are impedance and matching? Why is it necessary to achieve impedance matching in transformers? http://bbs.hcbbs.com/viewthread.php?tid=425160&highlight 81、【Daily Question 20090326】Guess what this is? http://bbs.hcbbs.com/viewthread.php?tid=426110&highlight 82、【Daily Question 20090327】Why do electrical installations often suffer from overheating problems? http://bbs.hcbbs.com/viewthread.php?tid=427323&highlight 83、【Daily Question 20090329】Guess what kind of valve this is? http://bbs.hcbbs.com/viewthread.php?tid=428648&highlight 84、【Daily Question 20090330】Guess what kind of pump this is? http://bbs.hcbbs.com/viewthread.php?tid=429496&highlight 85、【Daily Question 20090331】Guess what this is? http://bbs.hcbbs.com/viewthread.php?tid=430569&highlight April 86, 【Daily Question 20090402】Is the no-load speed of a DC motor also inversely proportional to the number of pole pairs? http://bbs.hcbbs.com/thread-432806-1-1.html November 3, 2010: The Daily Question activity was restarted. Here is the summary index post: 1. [Daily Question 20101103] Why don’t IT systems prefer to have a neutral wire? http://bbs.hcbbs.com/thread-754965-1-1.html 2. 【Daily Question 20101104】Should the doors of a substation open outward or inward? http://bbs.hcbbs.com/thread-755273-1-1.html 3. [Daily Question 20101105] Should the grounding resistance of pipeline networks be based on the 08 standard of 10Ω or the 88 standard of 4Ω? http://bbs.hcbbs.com/thread-755730-1-1.html 4. 【Daily Question 20101106】High and low backup protection for transformers http://bbs.hcbbs.com/thread-756201-1-1.html 5. 【Daily Question 20101107】Is it easier to maintain a 250KW motor at 10KV or at 400V? http://bbs.hcbbs.com/thread-756660-1-1.html 6. 【Daily Question 20101108】What is SPD? http://bbs.hcbbs.com/viewthread.php?tid=757050&extra=page%3D1%26amp%3Bfilter%3Dtype%26amp%3Btypeid%3D2 7. [Daily Question 20101109] During the power-up of a transformer, the inrush current is very large; why doesn’t the differential protection activate? http://bbs.hcbbs.com/thread-757632-1-1.html 8. [Daily Question 20101115] What are the different safety colors and what do they mean? http://bbs.hcbbs.com/thread-760526-1-1.html 9. [Daily Question 20101117] How is the CT polarity determined? http://bbs.hcbbs.com/thread-761317-1-1.html 10. 【Daily Question 20101118】Is it better to use single-strand wire or multi-strand wire for socket and switch wires in hospitals? http://bbs.hcbbs.com/thread-762076-1-1.html 11. 【Daily Question 20101119】Does an inverter save electricity? http://bbs.hcbbs.com/thread-762499-1-1.html 12. 【Daily Question 20101125】What are the types of melts? Give a brief overview of the specifications and features. http://bbs.hcbbs.com/thread-766347-1-1.html 13. 【Daily Question 20101126】What are the disadvantages of dust accumulating on motor windings? http://bbs.hcbbs.com/thread-766348-1-1.html 14. 【Daily Question 20101129】What type of work permit is required for the maintenance and repair of 380V electric actuators? http://bbs.hcbbs.com/thread-767871-1-1.html