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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 transformer winding to which voltage is supplied is called the _____ winding.






2. Transformer losses are classified as _____ and _____.






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






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






5. Divergence of the magnetic field causes this






6. 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






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






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






9. _____ currents are reduced by laminating the core.






10. 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 _____.






11. A system of conductors in which at least one conductors or point (usually the middle wire or neutral point of a transformer or generator windings) is intentionally grounded either solididly or through a current-limiting device.






12. Central magnetic core made of






13. 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.






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






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






16. A part of a circuit made of a low melting point material so that it will melt and break the circuit when a specified current exceeded. Always the weakest point in the circuit.






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






18. An instrument used to measure electrical current.






19. Transformers designed for 4800 volt primary operation - but the secondaries are connected 240/480 volts. Winding ratio is 10:1






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






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






22. If the transformer is used as a _____ transformer - the high voltage winding is the primary.






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






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






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






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






27. A single electrical circuit.






28. A ___________ transformer is a continuously adjustable Autotransformer.






29. _____ shows that the voltages across the windings of a transformer are directly proportional to the turns in each winding.






30. 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






31. 3 types of transformers






32. The terminals of the high voltage winding are marked _____.






33. A simple design has a core within each coil






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






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






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






37. The 3 principle components of a transformer






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






39. Insulated primary and secondary coils are in close proximity to each other - no iron core and very innefficient






40. 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






41. The number of turns can be adjusted in these types of transformers






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






43. A choke coil uses this to induce current






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






45. The relationship between current and voltage in the coils are inverse






46. How a variable degree of core saturation is accomplished in a saturable reactor?






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






48. What does transformer efficiency mean?






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






50. has a laminated iron core (layers of metal plates)







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