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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. What is a rotation meter?
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
closed-ended core (square/doughnut shaped)
coercivity
High voltage
2. The output which can be delivered for the time specified at rated secondary voltage and rated frequency without exceeding the specified temperature limitations.
grounded (Earthed)
Autotransformer
secondary coil
rated KVA of a transformer
3. How the voltage and the number of turns are related for the voltage related to turn ratio
directly proportional
coercivity
leakage flux
class 400 transformers
4. Waste of power known as transformer loss - often produced by closed-ended core
polarity
eddy currents
high frequency transformer
magnetic field
5. 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
air core
Hysteresis - Eddy - Current
high frequency transformer
How a transformer works
6. The winding to which voltage is supplied is called the _____ winding.
Measuring Equipment
class 400 transformers
Primary
shell core
7. 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
Class 200 transformers
continuous path
primary winding
short circuit
8. How a variable degree of core saturation is accomplished in a saturable reactor?
one coils serves as the primary and secondary windings
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
by varying the size of the applied DC
Copper Losses - Core Losses
9. Function of the dielectric oil
Eh/Ex=Th/Tx
Insulates - cools transformer by convection - dissipates heat
Copper Losses - Core Losses
ammeter
10. 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
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
open-ended core
Ip Ns = Is Np
Class 200 transformers
11. Copper loss is known as _____ loss.
Same
Voltage - Current
magnetic flux
12. Is concentrated in the metal core
magnetic field
Same
coercivity
variable
13. The voltage induced in the coil is directly proportional to this
copper losses (I2R); hysteresis losses (lagging losses); and eddy current losses (swirling currents)
the number of turns in the coil
short circuit
class 400 transformers
14. _____ shows that the voltamperes of the primary of a transformer equal the voltamperes of the secondary of a transformer.
Exciting Current
Eh - lH = Ex - lX
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
Class 200 transformers
15. Provides the ratio between the applied primary voltage and the induced secondary voltage as result of the turns ratio
Primary
voltage ralated to turns ratio
ammeter
CORE: Core losses are caused by eddy currents set up by the magnetic field.
16. Used to increase the magnetic flux in a transformer
grounded (Earthed)
central magnetic core
air core
rating
17. 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
Primary
shell core
Electromagnet
saturable reactor
18. Autotransformers are not safe when they supply a _____ voltage from a high voltage source.
Low
CORE: Core losses are caused by eddy currents set up by the magnetic field.
short circuit
voltage ralated to turns ratio
19. _____ currents are reduced by laminating the core.
closed-ended core
Secondary
Eddy
hysteresis losses (lagging losses)
20. The magnetic lines of force that flow from the north pole of a magnet and return to the south pole.
flux
High voltage
Choke coil
air core
21. A single electrical circuit.
transformers efficiency law
grounded (Earthed)
closed-ended core (square/doughnut shaped)
phase
22. This type of transformer power loss is caused by the continually changing AC current movement which constantly magnetizes/demagnetizes/re-magnetizes
Secondary
open-ended core
hysteresis losses (lagging losses)
closed-ended core
23. Anything above 600 volts is _____?
Choke coil
constant current transfomers
High voltage
Primary
24. ___________ is often used in laminated cores - increases electrical resistance which decreases eddy currents
silicon steel
by using silicon iron core
Measuring Equipment
class 400 transformers
25. Some losses occur in all transformers. These losses are classified as copper losses and _____ losses.
Voltage - Current
shell core
directly proportional
CORE: Core losses are caused by eddy currents set up by the magnetic field.
26. How coils serve as the primary and secondary windings for an autotransformer
Eddy
one coils serves as the primary and secondary windings
polarity
Hysteresis
27. The winding to which the load is connected is called the _____ winding.
Secondary
directly proportional
primary winding
one coils serves as the primary and secondary windings
28. 3 types of transformers
step-up (high voltage) transformers - step down transformer - autotransformer
by varying the size of the applied DC
X1 - X2...
Step-up
29. A choke coil uses this to induce current
closed-ended core
Electromagnet
an iron core and coil
high frequency transformer
30. A transformer rated at 500KVA and below used for voltage transformation on the distribuition system.
Distribution transformer
A small three-phase meter used to determine the direction of phase rotation on circuits or transformer banks.
hysteresis losses (lagging losses)
by varying the size of the applied DC
31. A ___________ transformer is a continuously adjustable Autotransformer.
How a transformer works
change the input voltage
class 400 transformers
variable
32. A stationary device for transferring alternating current electrical energy from one circuit to another circuit by electromagnetic means.
Transformer
Current
Aire core -open ended core -closed ended core (square/doughnut shaped) -shell core
rating
33. 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.
silicon steel
constant current transfomers
Exciting Current
Voltage
34. Kind of wire is the secondary coil in a transformer
High voltage
thin copper wire coated with insulated material (shellac or enamel)
Ip Ns = Is Np
magnetic flux
35. A magnetic field changing with respect to the conductor will generate a _____ in the conductor.
Voltage
Measuring
Exciting
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
36. 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.
central magnetic core
closed-ended core
Transformer
Secondary
37. For a step up and step down transformer if the turns ratio is constant this is the only way to change the output voltage
change the input voltage
shell core
air core
Exciting
38. closed core with a top and bottom. It directs the magnetic field towards the primary and secondary coils and increases the field stregnth
rated KVA of a transformer
Transformer
closed-ended core (square/doughnut shaped)
Secondary
39. A partial or total local failure in the insulation or continuity of a conductor.
coercivity
Primary
5
fault
40. The entire transformer is placed in a metal tank then immersed in ________.
one coils serves as the primary and secondary windings
by varying the size of the applied DC
Short Circuited: Unless the secondary winding is short-circuited - a high open circuit voltage that can be dangerous will exist.
dielectric oil
41. 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
primary coil - secondary coil - central magnetic core
short circuit
an iron core and coil
42. Transformer losses are classified as _____ and _____.
Exciting Current
Primary
Copper Losses - Core Losses
Eh/Ex=Th/Tx
43. An electromagnetic device that operates on the principle of self induction. It uses AC.
air core
Transformer
Choke coil
Same
44. Transformers designed for 4800 volt primary operation - but the secondaries are connected 240/480 volts. Winding ratio is 10:1
the number of turns of wire in the primary and secondary coils
hysteresis losses (lagging losses)
central magnetic core
class 400 transformers
45. The input side that attaches to the AC supply it recieves the electrical energy or incoming voltage
the number of turns in the coil
air core
primary coil
The ratio of useful power output to its total power input.
46. The terminals of the high voltage winding are marked _____.
Voltage - Current
H1 - h2...
leg(s)
wigginton
47. The formula for the current related to voltage law
rated KVA of a transformer
current related to voltage law
highly permeable material - iron or stalloy
Vs Ip = Vp Is
48. The total numbre of lines or force issuing from a pole. (north or south)
leg(s)
Hysteresis - Eddy - Current
Eddy
magnetic flux
49. A transformer loses less than _% in energy
rated KVA of a transformer
5
Transformer
low rententivity
50. An instrument used to measure electrical current.
transformers efficiency
ammeter
ratio of a transformer
closed-ended core