SUBJECTS
|
BROWSE
|
CAREER CENTER
|
POPULAR
|
JOIN
|
LOGIN
Business Skills
|
Soft Skills
|
Basic Literacy
|
Certifications
About
|
Help
|
Privacy
|
Terms
|
Email
Search
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 transformer is a device that has no moving parts and that transfers energy from one circuit to another by _____.
saturable reactor
leg(s)
Voltage - Current
Electromagnetic Induction.
2. A simple design has a core within each coil
The ratio of useful power output to its total power input.
open-ended core
saturable reactor
flux
3. Two coils wound on a closed iron core form a ________.
magnetic field
silicon steel
Simple Transformer
die to leakage flux
4. Copper loss is known as _____ loss.
Measuring
one coils serves as the primary and secondary windings
die to leakage flux
5. Reference to a jumper or conductor - to or from a piece of electrical equipment.
a magnetic field that varies quickly in direction and stregnth
Autotransformer
leg(s)
Hysteresis
6. It refers to the direction of current flow in a closed circuit.
leg(s)
Step-down
polarity
thin copper wire coated with insulated material (shellac or enamel)
7. A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means.
leakage flux
Primary
grounded system
Transformer
8. The output rating of a transformer is based upon the maximum _____ the transformer is capable of carrying without exceeding a certain temperature rise.
constant current transfomers
variable transformers
primary coil
Current
9. How the voltage and the number of turns are related for the voltage related to turn ratio
directly proportional
current related to turns ratio law
Hysteresis - Eddy - Current
Primary
10. The formula for the current related to voltage law
low rententivity
a magnetic field that varies quickly in direction and stregnth
Secondary
Vs Ip = Vp Is
11. How a variable degree of core saturation is accomplished in a saturable reactor?
central magnetic core
by varying the size of the applied DC
fault
constant current transfomers
12. The terminals of the high voltage winding are marked _____.
H1 - h2...
Hysteresis
Insulates - cools transformer by convection - dissipates heat
short circuit
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)
Exciting Current
wigginton
central magnetic core
closed-ended core (square/doughnut shaped)
14. The 3 principle components of a transformer
by varying the size of the applied DC
Exciting
Copper Losses - Core Losses
primary coil - secondary coil - central magnetic core
15. _____ shows that the voltamperes of the primary of a transformer equal the voltamperes of the secondary of a transformer.
by varying the size of the applied DC
Step-up
wigginton
Eh - lH = Ex - lX
16. Determines if the transformer is a step up or step down transformer
the number of turns of wire in the primary and secondary coils
short circuit
one coils serves as the primary and secondary windings
Step-up
17. How coercivity is minimized
by using silicon iron core
Simple Transformer
change the input voltage
Class 200 transformers
18. Insulated primary and secondary coils are in close proximity to each other - no iron core and very innefficient
air core
leg(s)
Measuring
closed-ended core (square/doughnut shaped)
19. The total numbre of lines or force issuing from a pole. (north or south)
ratio of a transformer
shell core
magnetic flux
closed-ended core (square/doughnut shaped)
20. 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
grounded (Earthed)
hysteresis losses (lagging losses)
closed-ended core
directly proportional
21. Autotransformers are not safe when they supply a _____ voltage from a high voltage source.
Low
wigginton
current related to turns ratio law
Eh/Ex=Th/Tx = (240/120 = 400/Tx) - 240 TX = 48000 - Tx = 48000/240 = 200 turns
22. The current related to turns ratio law
secondary coil
silicon steel
Volt-Amperes (Eh-lh=ExLx)
Ip Ns = Is Np
23. 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
voltage ralated to turns ratio
Secondary
How a transformer works
24. The number of turns can be adjusted in these types of transformers
Electromagnetic Induction.
Vs Ns = Vp Np
variable transformers
air core
25. A designated limit of operating characteristics based on definite conditions.
rating
air core
Same
26. A choke coil uses this to induce current
Low
an iron core and coil
change the input voltage
leakage flux
27. With no load on the secondary winding - a small current flows in the primary called _____ _____.
5
Exciting Current
closed-ended core
current related to turns ratio law
28. The winding to which the load is connected is called the _____ winding.
step-up (high voltage) transformers - step down transformer - autotransformer
Class 200 transformers
Primary
Secondary
29. An electromagnetic device that operates on the principle of self induction. It uses AC.
Choke coil
Current
Primary
Measuring
30. This is the most advanced and most efficient type of tansformer; it is commonly used in x-ray equipment
closed-ended core
shell core
central magnetic core
wigginton
31. A partial or total local failure in the insulation or continuity of a conductor.
fault
Eh/Ex=Th/Tx = (240/120 = 400/Tx) - 240 TX = 48000 - Tx = 48000/240 = 200 turns
Measuring
closed-ended core
32. Transformer losses are classified as _____ and _____.
closed-ended core (square/doughnut shaped)
Simple Transformer
Copper Losses - Core Losses
step-up (high voltage) transformers - step down transformer - autotransformer
33. 3 types of transformers
Hysteresis - Eddy - Current
Low
continuous path
step-up (high voltage) transformers - step down transformer - autotransformer
34. The formula for the voltage related to turns ratio
Vs Ns = Vp Np
grounded system
High voltage
polarity
35. The relationship between amperage flowing through the coils and the number of turns on individual coils is inverse
Kilovolt -- Amperes (kVA)
grounded system
current related to turns ratio law
hysteresis losses (lagging losses)
36. _____ shows that the voltages across the windings of a transformer are directly proportional to the turns in each winding.
Step-up
Eh/Ex=Th/Tx
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
transformers efficiency law
37. Modern; extremely efficient-more effective coupling between primary and secondary coils; smaller and lighter
high frequency transformer
fault
Copper Losses - Core Losses
the number of turns in the coil
38. If the transformer is used as a _____ transformer - the high voltage winding is the primary.
Step-down
by varying the size of the applied DC
Eh/Ex=Th/Tx
Voltage
39. Central magnetic core made of
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
shell core
highly permeable material - iron or stalloy
magnetic flux
40. Defined as the ratio of the power output to the power input (in a closed circuit containing resistance)
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
voltage ralated to turns ratio
transformers efficiency law
Hysteresis - Eddy - Current
41. 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.
electromagnetic mutual induction without loosing too much energy
Measuring Equipment
ratio of a transformer
fuse
42. The 4 types of transformer cores
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
by varying the size of the applied DC
How a transformer works
polarity
43. 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
constant current transfomers
Volt-Amperes (Eh-lh=ExLx)
Electromagnetic Induction.
saturable reactor
44. 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
Hysteresis
low rententivity
dielectric oil
Step-up
45. Used to increase the magnetic flux in a transformer
central magnetic core
high frequency transformer
Simple Transformer
46. The characteristic that requires energy to carry out the constant reorientation of the magnetic dipoles in the hysteresis loss
Transformer
coercivity
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
Electromagnet
47. The simplest type of transformer core
variable
air core
How a transformer works
primary coil
48. The entire transformer is placed in a metal tank then immersed in ________.
the number of turns in the coil
Kilovolt -- Amperes (kVA)
dielectric oil
Measuring Equipment
49. Hysteresis Loss can be reduced by using a core with this feature
low rententivity
Insulates - cools transformer by convection - dissipates heat
Secondary
Voltage - Current
50. Transformers designed for 4800 volt primary operation - but the secondaries are connected 240/480 volts. Winding ratio is 10:1
Class 200 transformers
by varying the size of the applied DC
wigginton
class 400 transformers