Test for knowledge of the device and the principle of operation of the transformer

1). In a certain loaded transformer, the secondary voltage is one-fourth of the primary voltage, the secondary current in this case:
a) a quarter of the primary current
b) four times the primary current
c) equal to the primary current
d) one fourth of the primary current or equal to the primary current

2). Which of the list is variable loss?
a) loss of eddy currents
b) loss of hysteresis
c) loss in copper in the shunt field
d) losses in copper winding

3). The noise generated by vibrations of the steel lamellas of the core, caused by magnetic forces, is called
a) magnetostriction
b) whistle
c) hum
d) zoom

4). The primary winding of a power transformer should always be:
a) open
b) short-circuited
c) switchable
d) united

5). Eddy current loss depends on:
a) frequencies
b) flux density
c) thickness
d) all of the above

6). The hysteresis loss will depend on:
a) f
b) f²
c) f³
d) f ^ 1.6

7). Total core loss is also called ———?
a) loss of eddy currents
b) hysteresis loss 
c) magnetic losses
d) loss of copper

eight). The maximum efficiency of the transformer takes place when copper loss _________ iron loss?
a) more than
b) less than
c) equal
d) any of the above

nine). The main function of the transformer is to change

a) power level
b) power factor
c) voltage level
d) frequency

ten). The flux in the transformer core depends mainly on:
a) supply voltage
b) supply voltage and frequency
c) supply voltage, frequency and load
d) supply voltage and load

See the answers in the comments ⏬



Total comments: 2

  • leader
    By leader Added on April 12, 2020 at 19:28

    1) -b
    2) -d -Losses in copper are directly proportional to the square of the current in the winding. Therefore, as the load changes, they also change.
    3) -v
    4) -g
    5) -d-Eddy current losses will depend on frequency, flux density and eddy current contour
    6) -a-P (h) = K (h) * B (m) ^ 1.6 * f so the hysteresis loss will depend on the frequency
    7) -c-Since the losses in iron are proportional to the flux density or flux, they are also called magnetic losses. Total core loss or magnetic loss consists of eddy current loss and hysteresis loss.
    8) -c-Condition of maximum efficiency: copper losses = iron losses or variable losses are equal to fixed losses.
    9) -v- The transformer can be used to increase or decrease the voltage without changing the frequency.
    10) -b

    To answer
  • Андрей
    By Andrey Added on April 13, 2020 at 16:41

    good day
    2-a, b, c, d
    3 -a
    4- c, d

    To answer

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