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Transformers

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
  • If you are not ready to take this test, you can study here.
  • Match each statement with the correct term.
  • Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.
1. A transformer primary (H) that has 400 turns is wound to step the voltage down from 240 volts to 120 volts. The number or turns (TX) required in the secondary (X) winding is _____.






2. The 3 types of transformer power loss






3. The shape of the core of the transformer ensures a ______________ for the magnetic flux with maximum concentration within the core and minimum leakage of the air






4. What does transformer efficiency mean?






5. An electromagnetic device that operates on the principle of self induction. It uses AC.






6. If the transformer is used as a _____ transformer - the low voltage winding is the primary.






7. A single electrical circuit.






8. Core losses are _____ loss and _____ - _____ loss.






9. Instrument transformers reduce high voltages and currents to safe - usable values for the operation of _____ equipment.






10. This core is more efficient than the air core because the iron core in each coil intensifies the magnetic flux in both primary and secondary coils when they become magnetized as current flows through each set of coils






11. A simple design has a core within each coil






12. A transformer rated at 500KVA and below used for voltage transformation on the distribuition system.






13. Some losses occur in all transformers. These losses are classified as copper losses and _____ losses.






14. A designated limit of operating characteristics based on definite conditions.






15. Defined as the ratio of the power output to the power input (in a closed circuit containing resistance)






16. The winding to which the load is connected is called the _____ winding.






17. A magnet made by winding a coil of wire around a soft iron core. Current passed through this winding produces magnetic lines of force in the coil.






18. Anything above 600 volts is _____?






19. Modern; used to control filament circuit; replaced both the rheostat and choke coil; operated on the electromagnetic principle that if an iron core within or near a coil is saturated with magnetic flux by an independed source of direct current - the






20. The total numbre of lines or force issuing from a pole. (north or south)






21. A large amount of power wasted with the open-ended core






22. In a transformer the _____ current will always flow in such a direction that its magnetizing action will oppose the magnetizing action of the primary winding.






23. With no load on the secondary winding - a small current flows in the primary called _____ _____.






24. The turns of both windings are cut by the same flux; therefore the induced emf in each turn of both windings is the _____.






25. An abnormal connection of relative low resistance - whether made accidentally or intentionally - between two point of different potential in a circuit.






26. The output rating of a transformer is based upon the maximum _____ the transformer is capable of carrying without exceeding a certain temperature rise.






27. The terminals of the low voltage winding are marked _____.






28. The volt-amperes of the primary of a transformer is equal to the _____ - _____ output of the transformer.






29. A variable transformer is a continuously adjustable _____ - has the primary winding and secondary winding electrically connected.






30. Both the primary and secondary coils in a transformer are arranged around this






31. _____ shows that the voltamperes of the primary of a transformer equal the voltamperes of the secondary of a transformer.






32. The formula for the voltage related to turns ratio






33. Reference to a jumper or conductor - to or from a piece of electrical equipment.






34. Copper loss is known as _____ loss.






35. How coercivity is minimized






36. The magnetic lines of force that flow from the north pole of a magnet and return to the south pole.






37. Kind of wire is the secondary coil in a transformer






38. A test instrument used to indicate low voltage potentials in the range of 110 to 600 volts either alternating or direct current. (slang term: wiggy)






39. To minimize ________ in transformer construction - the primary and secondary windings are placed on the same leg(s) of the core.






40. 3 types of transformers






41. Current flows through the primary winding in response to primary voltage and sets up a magnetic field that varies in direction and stregnth. under the influence of the changing magnetic field an AC voltage/kv is induced across the secondary coil by e






42. The voltage induced in the coil is directly proportional to this






43. Central magnetic core made of






44. A transformer is a device that either increases or decreases alternating current and voltage using this principle






45. Transformers with 4800 volt primaries and 120/240 volt secondaries - either pole or subway type - with two secondary windings terminating at internal links which provide for parallel operation of the secondary windings at 120 volts or series operatio






46. Autotransformers are not safe when they supply a _____ voltage from a high voltage source.






47. Hysteresis Loss can be reduced by using a core with this feature






48. A choke coil uses this to induce current






49. Used to increase the magnetic flux in a transformer






50. Modern; extremely efficient-more effective coupling between primary and secondary coils; smaller and lighter







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