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






2. 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






3. 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






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






5. An instrument used to measure electrical current.






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






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






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






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






10. The formula for the voltage related to turns ratio






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






12. Is concentrated in the metal core






13. 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






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






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






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






17. both coils in this core are heavily insulated






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






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






20. _____ currents are reduced by laminating the core.






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






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






23. Function of the dielectric oil






24. The current related to turns ratio law






25. The winding to which voltage is supplied is called the _____ winding.






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






27. 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.






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. 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 _____.






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






31. Connected to earth or to some conducting body which serves in place of the earth.






32. A ___________ transformer is a continuously adjustable Autotransformer.






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






34. Divergence of the magnetic field causes this






35. Provides the ratio between the applied primary voltage and the induced secondary voltage as result of the turns ratio






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






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






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






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






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






41. 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






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






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






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






45. The simplest type of transformer core






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






47. A transformer loses less than _% in energy






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






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






50. Transformer losses are classified as _____ and _____.







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