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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. A partial or total local failure in the insulation or continuity of a conductor.
class 400 transformers
flux leakage
fault
Transformer
2. The 3 principle components of a transformer
primary coil - secondary coil - central magnetic core
fault
Transformer
3. An abnormal connection of relative low resistance - whether made accidentally or intentionally - between two point of different potential in a circuit.
hysteresis losses (lagging losses)
leg(s)
short circuit
Choke coil
4. Connected to earth or to some conducting body which serves in place of the earth.
air core
Measuring
Ip Ns = Is Np
grounded (Earthed)
5. 3 types of transformers
step-up (high voltage) transformers - step down transformer - autotransformer
leg(s)
dielectric oil
highly permeable material - iron or stalloy
6. The capacity of a transformer is rated in ____ _____.
saturable reactor
Kilovolt -- Amperes (kVA)
Hysteresis - Eddy - Current
Step-down
7. The turns of both windings are cut by the same flux; therefore the induced emf in each turn of both windings is the _____.
dielectric oil
closed-ended core
Same
leg(s)
8. A large amount of power wasted with the open-ended core
die to leakage flux
secondary coil
X1 - X2...
highly permeable material - iron or stalloy
9. The current flowing through the primary winding - in response to the applied primary voltage - sets this up
change the input voltage
ammeter
a magnetic field that varies quickly in direction and stregnth
dielectric oil
10. has a laminated iron core (layers of metal plates)
variable
closed-ended core
one coils serves as the primary and secondary windings
low rententivity
11. Modern; extremely efficient-more effective coupling between primary and secondary coils; smaller and lighter
high frequency transformer
silicon steel
Secondary
Secondary
12. Copper loss is known as _____ loss.
constant current transfomers
die to leakage flux
Ip Ns = Is Np
13. The characteristic that requires energy to carry out the constant reorientation of the magnetic dipoles in the hysteresis loss
Hysteresis
fuse
Eddy
coercivity
14. The current related to turns ratio law
5
Secondary
eddy currents
Ip Ns = Is Np
15. A transformer is a device that has no moving parts and that transfers energy from one circuit to another by _____.
dielectric oil
continuous path
The ratio of useful power output to its total power input.
Electromagnetic Induction.
16. 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
open-ended core
Step-down
Eddy
thin copper wire coated with insulated material (shellac or enamel)
17. This is the most advanced and most efficient type of tansformer; it is commonly used in x-ray equipment
Eddy
shell core
Exciting
eddy currents
18. Both the primary and secondary coils in a transformer are arranged around this
Step-up
central magnetic core
Voltage
a magnetic field that varies quickly in direction and stregnth
19. How the voltage and the number of turns are related for the voltage related to turn ratio
eddy currents
directly proportional
closed-ended core
closed-ended core (square/doughnut shaped)
20. A magnetic field changing with respect to the conductor will generate a _____ in the conductor.
Exciting Current
Voltage
high frequency transformer
Eddy
21. Insulated primary and secondary coils are in close proximity to each other - no iron core and very innefficient
voltage ralated to turns ratio
leakage flux
Choke coil
air core
22. Autotransformers are not safe when they supply a _____ voltage from a high voltage source.
Low
class 400 transformers
high frequency transformer
magnetic flux
23. The relationship between current and voltage in the coils are inverse
Secondary
Same
constant current transfomers
current related to voltage law
24. Central magnetic core made of
High voltage
highly permeable material - iron or stalloy
the number of turns of wire in the primary and secondary coils
thin copper wire coated with insulated material (shellac or enamel)
25. 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.
Secondary
an iron core and coil
Kilovolt -- Amperes (kVA)
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
26. Two coils wound on a closed iron core form a ________.
Insulates - cools transformer by convection - dissipates heat
Simple Transformer
change the input voltage
ammeter
27. Refers to the transformer's ability to avoid power loss (heat)
class 400 transformers
transformers efficiency
Voltage - Current
saturable reactor
28. The total numbre of lines or force issuing from a pole. (north or south)
Eh/Ex=Th/Tx
magnetic flux
primary coil - secondary coil - central magnetic core
current related to turns ratio law
29. Determines if the transformer is a step up or step down transformer
closed-ended core
the number of turns of wire in the primary and secondary coils
current related to voltage law
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
30. With no load on the secondary winding - a small current flows in the primary called _____ _____.
magnetic flux
Exciting Current
closed-ended core
Ip Ns = Is Np
31. What is a rotation meter?
primary winding
thin copper wire coated with insulated material (shellac or enamel)
shell core
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
32. 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
rating
coercivity
Class 200 transformers
Voltage - Current
33. A designated limit of operating characteristics based on definite conditions.
rating
an iron core and coil
primary coil
current related to voltage law
34. The formula for the current related to voltage law
Eh/Ex=Th/Tx
Vs Ip = Vp Is
leakage flux
wigginton
35. The entire transformer is placed in a metal tank then immersed in ________.
dielectric oil
leakage flux
open-ended core
by using silicon iron core
36. 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
Eh - lH = Ex - lX
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
saturable reactor
How a transformer works
37. ___________ is often used in laminated cores - increases electrical resistance which decreases eddy currents
Kilovolt -- Amperes (kVA)
Eh/Ex=Th/Tx = (240/120 = 400/Tx) - 240 TX = 48000 - Tx = 48000/240 = 200 turns
silicon steel
constant current transfomers
38. Transformers designed for 4800 volt primary operation - but the secondaries are connected 240/480 volts. Winding ratio is 10:1
Choke coil
Insulates - cools transformer by convection - dissipates heat
How a transformer works
class 400 transformers
39. The magnetic lines of force that flow from the north pole of a magnet and return to the south pole.
leakage flux
flux
Hysteresis
transformers efficiency
40. The formula for the voltage related to turns ratio
saturable reactor
Vs Ns = Vp Np
Vs Ip = Vp Is
open-ended core
41. The input side that attaches to the AC supply it recieves the electrical energy or incoming voltage
fuse
primary coil
Measuring
Vs Ip = Vp Is
42. A transformer is a device that either increases or decreases alternating current and voltage using this principle
electromagnetic mutual induction without loosing too much energy
H1 - h2...
ratio of a transformer
constant current transfomers
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.
grounded system
Ip Ns = Is Np
thin copper wire coated with insulated material (shellac or enamel)
Eh/Ex=Th/Tx = (240/120 = 400/Tx) - 240 TX = 48000 - Tx = 48000/240 = 200 turns
44. What does transformer efficiency mean?
The ratio of useful power output to its total power input.
How a transformer works
class 400 transformers
by using silicon iron core
45. A ___________ transformer is a continuously adjustable Autotransformer.
Same
primary winding
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
variable
46. 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 _____.
hysteresis losses (lagging losses)
Eh/Ex=Th/Tx = (240/120 = 400/Tx) - 240 TX = 48000 - Tx = 48000/240 = 200 turns
Electromagnetic Induction.
Autotransformer
47. The turns ratio between the windings (primary & secondary) of a transformer unless otherwise specified.
ratio of a transformer
flux
variable transformers
the number of turns in the coil
48. A transformer loses less than _% in energy
fault
Measuring Equipment
Voltage
5
49. To minimize ________ in transformer construction - the primary and secondary windings are placed on the same leg(s) of the core.
flux leakage
open-ended core
Current
Simple Transformer
50. 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.
Secondary
Insulates - cools transformer by convection - dissipates heat
constant current transfomers