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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. The characteristic that requires energy to carry out the constant reorientation of the magnetic dipoles in the hysteresis loss






2. The turns ratio between the windings (primary & secondary) of a transformer unless otherwise specified.






3. The current related to turns ratio law






4. The energy is always transferred without a change in frequency - but usually with changes in _____ and _____.






5. Transformer losses are classified as _____ and _____.






6. The formula for the voltage related to turns ratio






7. 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 _____.






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






9. The loss of power required to reverse the core magnatism each time the current reverses. This loss is caused by friction between the molecules of iron as these particles are aligned first in one direction and the in the opposite direct as current dir






10. A transformer which when supplied from a constant potential source automatically maintans a constant current in its secondary circuit under varying conditions of load impedance. Used on series street light circuits.






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






12. The transformer winding to which the load is connected is called the _____ winding.






13. The 3 types of transformer power loss






14. How coercivity is minimized






15. A single electrical circuit.






16. 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






17. Determines if the transformer is a step up or step down transformer






18. The relationship between amperage flowing through the coils and the number of turns on individual coils is inverse






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. This type of transformer power loss is caused by the continually changing AC current movement which constantly magnetizes/demagnetizes/re-magnetizes






21. _____ currents are reduced by laminating the core.






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






23. A ___________ transformer is a continuously adjustable Autotransformer.






24. A simple design has a core within each coil






25. A transformer loses less than _% in energy






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






27. The output side it develops AC by electromagnetic mutual induction - Secondary voltage is induced in this coil






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






29. What does transformer efficiency mean?






30. This is the most advanced and most efficient type of tansformer; it is commonly used in x-ray equipment






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






32. A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means.






33. both coils in this core are heavily insulated






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






35. 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)






36. The winding of a transformer to which electrical energy is supplied.






37. An instrument used to measure electrical current.






38. Function of the dielectric oil






39. closed core with a top and bottom. It directs the magnetic field towards the primary and secondary coils and increases the field stregnth






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






41. Waste of power known as transformer loss - often produced by closed-ended core






42. How the voltage and the number of turns are related for the voltage related to turn ratio






43. A choke coil uses this to induce current






44. The simplest type of transformer core






45. The 3 principle components of a transformer






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






47. The entire transformer is placed in a metal tank then immersed in ________.






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






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






50. This type of core is moderately efficient due to closing the core and layering design which reduces power loss from less leakage flux which provides a continuous path for magnetic flux and an increase in field strength







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