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






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






3. 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






4. 3 types of transformers






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






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






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






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






9. 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 _____.






10. 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






11. A ___________ transformer is a continuously adjustable Autotransformer.






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






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






14. How coils serve as the primary and secondary windings for an autotransformer






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






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






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






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






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






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






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






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






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






24. An instrument used to measure electrical current.






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






26. 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






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






28. It refers to the direction of current flow in a closed circuit.






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






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






31. A magnet made by winding a coil of wire around a soft iron core. Current passed through this winding produces magnetic lines of force in the coil.






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






33. The simplest type of transformer core






34. Copper loss is known as _____ loss.






35. _____ currents are reduced by laminating the core.






36. How coercivity is minimized






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






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






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






40. The current related to turns ratio law






41. A transformer loses less than _% in energy






42. 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






43. 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.






44. Used to increase the magnetic flux in a transformer






45. 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)






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






47. The formula for the voltage related to turns ratio






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






49. Transformer losses are classified as _____ and _____.






50. Anything above 600 volts is _____?