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






2. 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.






3. How coercivity is minimized






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






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






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






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






8. both coils in this core are heavily insulated






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






10. Anything above 600 volts is _____?






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






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






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






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






15. 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






16. 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






17. Transformer losses are classified as _____ and _____.






18. 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






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






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






21. 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.






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






23. The output which can be delivered for the time specified at rated secondary voltage and rated frequency without exceeding the specified temperature limitations.






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






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






26. 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






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






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






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






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






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






32. Divergence of the magnetic field causes this






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






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






35. 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 _____.






36. 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






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






38. For a step up and step down transformer if the turns ratio is constant this is the only way to change the output voltage






39. 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.






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






41. The 3 principle components of a transformer






42. 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)






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






44. A simple design has a core within each coil






45. Used to increase the magnetic flux in a transformer






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






47. A transformer loses less than _% in energy






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






49. The current flowing through the primary winding - in response to the applied primary voltage - sets this up






50. A magnetic field changing with respect to the conductor will generate a _____ in the conductor.