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. The entire transformer is placed in a metal tank then immersed in ________.
by using silicon iron core
dielectric oil
Autotransformer
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
2. Waste of power known as transformer loss - often produced by closed-ended core
Eddy
eddy currents
step-up (high voltage) transformers - step down transformer - autotransformer
constant current transfomers
3. The output which can be delivered for the time specified at rated secondary voltage and rated frequency without exceeding the specified temperature limitations.
open-ended core
Measuring Equipment
rated KVA of a transformer
X1 - X2...
4. Determines if the transformer is a step up or step down transformer
H1 - h2...
by using silicon iron core
High voltage
the number of turns of wire in the primary and secondary coils
5. The terminals of the high voltage winding are marked _____.
H1 - h2...
Insulates - cools transformer by convection - dissipates heat
eddy currents
shell core
6. 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
central magnetic core
open-ended core
one coils serves as the primary and secondary windings
Low
7. What is a rotation meter?
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
Simple Transformer
Voltage
Eddy
8. 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
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
Class 200 transformers
Kilovolt -- Amperes (kVA)
central magnetic core
9. The volt-amperes of the primary of a transformer is equal to the _____ - _____ output of the transformer.
5
dielectric oil
Volt-Amperes (Eh-lh=ExLx)
rating
10. It refers to the direction of current flow in a closed circuit.
polarity
current related to turns ratio law
Voltage - Current
voltage ralated to turns ratio
11. Function of the dielectric oil
high frequency transformer
Low
Insulates - cools transformer by convection - dissipates heat
air core
12. How coils serve as the primary and secondary windings for an autotransformer
Current
Primary
one coils serves as the primary and secondary windings
flux
13. A partial or total local failure in the insulation or continuity of a conductor.
air core
fault
Volt-Amperes (Eh-lh=ExLx)
one coils serves as the primary and secondary windings
14. The 4 types of transformer cores
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
Class 200 transformers
Hysteresis
phase
15. This type of transformer power loss is caused by the continually changing AC current movement which constantly magnetizes/demagnetizes/re-magnetizes
hysteresis losses (lagging losses)
saturable reactor
central magnetic core
Vs Ip = Vp Is
16. How a variable degree of core saturation is accomplished in a saturable reactor?
by varying the size of the applied DC
Ip Ns = Is Np
Secondary
Distribution transformer
17. 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
Electromagnetic Induction.
closed-ended core
ratio of a transformer
by using silicon iron core
18. A transformer is a device that either increases or decreases alternating current and voltage using this principle
Vs Ip = Vp Is
Electromagnet
electromagnetic mutual induction without loosing too much energy
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
19. Copper loss is known as _____ loss.
Class 200 transformers
hysteresis losses (lagging losses)
central magnetic core
20. Instrument transformers reduce high voltages and currents to safe - usable values for the operation of _____ _____.
primary winding
Ip Ns = Is Np
Measuring Equipment
Electromagnetic Induction.
21. The transformer winding to which voltage is supplied is called the _____ winding.
variable transformers
Eddy
Hysteresis - Eddy - Current
Primary
22. The terminals of the low voltage winding are marked _____.
Insulates - cools transformer by convection - dissipates heat
primary coil - secondary coil - central magnetic core
X1 - X2...
closed-ended core (square/doughnut shaped)
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
How a transformer works
flux leakage
shell core
Kilovolt -- Amperes (kVA)
24. Used to increase the magnetic flux in a transformer
Vs Ns = Vp Np
Transformer
central magnetic core
The ratio of useful power output to its total power input.
25. 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.
magnetic flux
Secondary
Electromagnet
open-ended core
26. What does transformer efficiency mean?
central magnetic core
The ratio of useful power output to its total power input.
shell core
Electromagnetic Induction.
27. The formula for the current related to voltage law
Primary
Vs Ip = Vp Is
step-up (high voltage) transformers - step down transformer - autotransformer
magnetic flux
28. Transformer losses are classified as _____ and _____.
Copper Losses - Core Losses
fuse
coercivity
die to leakage flux
29. A choke coil uses this to induce current
an iron core and coil
Ip Ns = Is Np
Eh/Ex=Th/Tx
Measuring
30. Some losses occur in all transformers. These losses are classified as copper losses and _____ losses.
CORE: Core losses are caused by eddy currents set up by the magnetic field.
change the input voltage
Exciting Current
magnetic field
31. 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
die to leakage flux
Hysteresis
Voltage
grounded (Earthed)
32. This is the most advanced and most efficient type of tansformer; it is commonly used in x-ray equipment
step-up (high voltage) transformers - step down transformer - autotransformer
change the input voltage
coercivity
shell core
33. 3 types of transformers
step-up (high voltage) transformers - step down transformer - autotransformer
continuous path
central magnetic core
5
34. The turns of both windings are cut by the same flux; therefore the induced emf in each turn of both windings is the _____.
Same
central magnetic core
voltage ralated to turns ratio
grounded system
35. A variable transformer is a continuously adjustable _____ - has the primary winding and secondary winding electrically connected.
fuse
rating
coercivity
Autotransformer
36. If the transformer is used as a _____ transformer - the low voltage winding is the primary.
the number of turns in the coil
Class 200 transformers
Hysteresis
Step-up
37. How the voltage and the number of turns are related for the voltage related to turn ratio
transformers efficiency law
Transformer
low rententivity
directly proportional
38. ___________ is often used in laminated cores - increases electrical resistance which decreases eddy currents
silicon steel
dielectric oil
Kilovolt -- Amperes (kVA)
Measuring
39. Central magnetic core made of
ammeter
saturable reactor
highly permeable material - iron or stalloy
rating
40. A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means.
Transformer
How a transformer works
Eddy
saturable reactor
41. Provides the ratio between the applied primary voltage and the induced secondary voltage as result of the turns ratio
change the input voltage
voltage ralated to turns ratio
highly permeable material - iron or stalloy
leakage flux
42. A magnetic field changing with respect to the conductor will generate a _____ in the conductor.
Hysteresis
Voltage
coercivity
a magnetic field that varies quickly in direction and stregnth
43. A transformer loses less than _% in energy
ammeter
Vs Ns = Vp Np
5
closed-ended core
44. For a step up and step down transformer if the turns ratio is constant this is the only way to change the output voltage
coercivity
change the input voltage
Secondary
Primary
45. The total numbre of lines or force issuing from a pole. (north or south)
magnetic flux
one coils serves as the primary and secondary windings
wigginton
die to leakage flux
46. closed core with a top and bottom. It directs the magnetic field towards the primary and secondary coils and increases the field stregnth
primary winding
Primary
closed-ended core (square/doughnut shaped)
leakage flux
47. If the transformer is used as a _____ transformer - the high voltage winding is the primary.
magnetic flux
the number of turns of wire in the primary and secondary coils
Step-down
die to leakage flux
48. The current flowing through the primary winding - in response to the applied primary voltage - sets this up
current related to voltage law
Hysteresis
highly permeable material - iron or stalloy
a magnetic field that varies quickly in direction and stregnth
49. Instrument transformers reduce high voltages and currents to safe - usable values for the operation of _____ equipment.
Step-down
Measuring
The ratio of useful power output to its total power input.
Same
50. Reference to a jumper or conductor - to or from a piece of electrical equipment.
leg(s)
Primary
electromagnetic mutual induction without loosing too much energy
the number of turns in the coil