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Test your basic knowledge |
Transformers
Start Test
Study First
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. An abnormal connection of relative low resistance - whether made accidentally or intentionally - between two point of different potential in a circuit.
short circuit
class 400 transformers
Autotransformer
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
2. A simple design has a core within each coil
open-ended core
saturable reactor
transformers efficiency
step-up (high voltage) transformers - step down transformer - autotransformer
3. The winding to which voltage is supplied is called the _____ winding.
leg(s)
high frequency transformer
Primary
Insulates - cools transformer by convection - dissipates heat
4. The 3 principle components of a transformer
rating
change the input voltage
open-ended core
primary coil - secondary coil - central magnetic core
5. A transformer is a device that has no moving parts and that transfers energy from one circuit to another by _____.
constant current transfomers
Electromagnetic Induction.
leakage flux
electromagnetic mutual induction without loosing too much energy
6. The input side that attaches to the AC supply it recieves the electrical energy or incoming voltage
Electromagnetic Induction.
primary coil
the number of turns in the coil
shell core
7. It refers to the direction of current flow in a closed circuit.
polarity
eddy currents
transformers efficiency
the number of turns in the coil
8. 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.
Secondary
low rententivity
Exciting
step-up (high voltage) transformers - step down transformer - autotransformer
9. 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.
transformers efficiency law
Measuring
constant current transfomers
Distribution transformer
10. Central magnetic core made of
Secondary
Volt-Amperes (Eh-lh=ExLx)
highly permeable material - iron or stalloy
Voltage - Current
11. A designated limit of operating characteristics based on definite conditions.
rating
Vs Ip = Vp Is
the number of turns in the coil
H1 - h2...
12. The characteristic that requires energy to carry out the constant reorientation of the magnetic dipoles in the hysteresis loss
The ratio of useful power output to its total power input.
closed-ended core
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
coercivity
13. 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)
Step-up
wigginton
Transformer
step-up (high voltage) transformers - step down transformer - autotransformer
14. The output side it develops AC by electromagnetic mutual induction - Secondary voltage is induced in this coil
air core
die to leakage flux
Copper Losses - Core Losses
secondary coil
15. This is the most advanced and most efficient type of tansformer; it is commonly used in x-ray equipment
shell core
hysteresis losses (lagging losses)
closed-ended core
Step-up
16. The transformer winding to which voltage is supplied is called the _____ winding.
Primary
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
flux
central magnetic core
17. The volt-amperes of the primary of a transformer is equal to the _____ - _____ output of the transformer.
class 400 transformers
central magnetic core
Measuring
Volt-Amperes (Eh-lh=ExLx)
18. A transformer is a device that either increases or decreases alternating current and voltage using this principle
current related to turns ratio law
Eh/Ex=Th/Tx
Step-up
electromagnetic mutual induction without loosing too much energy
19. both coils in this core are heavily insulated
Current
closed-ended core
fuse
Electromagnet
20. The relationship between current and voltage in the coils are inverse
grounded (Earthed)
current related to voltage law
CORE: Core losses are caused by eddy currents set up by the magnetic field.
low rententivity
21. has a laminated iron core (layers of metal plates)
closed-ended core
Measuring
leg(s)
Insulates - cools transformer by convection - dissipates heat
22. This type of transformer power loss is caused by the continually changing AC current movement which constantly magnetizes/demagnetizes/re-magnetizes
class 400 transformers
closed-ended core
hysteresis losses (lagging losses)
magnetic flux
23. _____ shows that the voltamperes of the primary of a transformer equal the voltamperes of the secondary of a transformer.
transformers efficiency
thin copper wire coated with insulated material (shellac or enamel)
Eh - lH = Ex - lX
one coils serves as the primary and secondary windings
24. How a variable degree of core saturation is accomplished in a saturable reactor?
by varying the size of the applied DC
fault
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
Current
25. A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means.
Secondary
Electromagnetic Induction.
Transformer
fuse
26. To prevent injury to personnel when servicing any equipment connected to a current transformer - the secondary winding must be ____ - _____.
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
The ratio of useful power output to its total power input.
Current
closed-ended core
27. 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
Eddy
closed-ended core
closed-ended core
Hysteresis
28. Insulated primary and secondary coils are in close proximity to each other - no iron core and very innefficient
leg(s)
Measuring Equipment
air core
Electromagnet
29. To minimize ________ in transformer construction - the primary and secondary windings are placed on the same leg(s) of the core.
Volt-Amperes (Eh-lh=ExLx)
flux leakage
class 400 transformers
Distribution transformer
30. A magnetic field changing with respect to the conductor will generate a _____ in the conductor.
the number of turns in the coil
eddy currents
hysteresis losses (lagging losses)
Voltage
31. A large amount of power wasted with the open-ended core
Secondary
die to leakage flux
Voltage - Current
Vs Ip = Vp Is
32. Anything above 600 volts is _____?
the number of turns in the coil
highly permeable material - iron or stalloy
High voltage
fault
33. The winding of a transformer to which electrical energy is supplied.
primary winding
short circuit
Secondary
Insulates - cools transformer by convection - dissipates heat
34. _____ shows that the voltages across the windings of a transformer are directly proportional to the turns in each winding.
grounded (Earthed)
Eh/Ex=Th/Tx
ratio of a transformer
Choke coil
35. Both the primary and secondary coils in a transformer are arranged around this
central magnetic core
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
Insulates - cools transformer by convection - dissipates heat
Measuring Equipment
36. The transformer winding to which the load is connected is called the _____ winding.
Secondary
High voltage
Low
one coils serves as the primary and secondary windings
37. 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.
Primary
air core
grounded system
flux leakage
38. An instrument used to measure electrical current.
ratio of a transformer
hysteresis losses (lagging losses)
ammeter
low rententivity
39. Reference to a jumper or conductor - to or from a piece of electrical equipment.
grounded (Earthed)
leg(s)
continuous path
Hysteresis - Eddy - Current
40. 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
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
short circuit
closed-ended core
41. The voltage induced in the coil is directly proportional to this
current related to voltage law
the number of turns in the coil
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
coercivity
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
grounded (Earthed)
Eh - lH = Ex - lX
Ip Ns = Is Np
change the input voltage
43. How coercivity is minimized
voltage ralated to turns ratio
by using silicon iron core
shell core
step-up (high voltage) transformers - step down transformer - autotransformer
44. Instrument transformers reduce high voltages and currents to safe - usable values for the operation of _____ _____.
air core
Measuring Equipment
flux
high frequency transformer
45. A transformer loses less than _% in energy
low rententivity
5
transformers efficiency
short circuit
46. Provides the ratio between the applied primary voltage and the induced secondary voltage as result of the turns ratio
rated KVA of a transformer
thin copper wire coated with insulated material (shellac or enamel)
voltage ralated to turns ratio
Step-up
47. Connected to earth or to some conducting body which serves in place of the earth.
central magnetic core
shell core
grounded (Earthed)
Vs Ip = Vp Is
48. The terminals of the low voltage winding are marked _____.
X1 - X2...
Step-down
flux
leg(s)
49. 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
Secondary
How a transformer works
Volt-Amperes (Eh-lh=ExLx)
dielectric oil
50. What does transformer efficiency mean?
The ratio of useful power output to its total power input.
Vs Ip = Vp Is
Voltage
Same