Test your basic knowledge |

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 is a device that has no moving parts and that transfers energy from one circuit to another by _____.






2. The formula for the voltage related to turns ratio






3. The 3 principle components of a transformer






4. To prevent injury to personnel when servicing any equipment connected to a current transformer - the secondary winding must be ____ - _____.






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






6. The 4 types of transformer cores






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






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






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






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






11. Used to increase the magnetic flux in a transformer






12. An instrument used to measure electrical current.






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






14. 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






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






16. The current related to turns ratio law






17. The formula for the current related to voltage law






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






19. 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






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






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






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






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






24. Two coils wound on a closed iron core form a ________.






25. both coils in this core are heavily insulated






26. Anything above 600 volts is _____?






27. Is concentrated in the metal core






28. 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






29. 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.






30. 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)






31. 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.






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






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






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






35. Central magnetic core made of






36. _____ currents are reduced by laminating the core.






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






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






39. 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






40. A simple design has a core within each coil






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






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






43. ___________ is often used in laminated cores - increases electrical resistance which decreases eddy currents






44. The capacity of a transformer is rated in ____ _____.






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






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






47. Copper loss is known as _____ loss.






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






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






50. When an alternating current is applied to the high-voltage (H) winding of a transformer with no load on the secondary (X) winding - a small current - called the _____ current - flows in the primary.