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54. The building electrical installation diagram is generally represented by (b).

A. elevation B. plan C. perspective D. detail

55. In the diagram with complicated wiring, the wire connection is indicated by dotted lines, and the numbering method in (a) is usually adopted.

A. Relative B. Absolute C. Order D. Logic

56. In the electrical diagram, where the dimension unit does not need (b), it must be indicated separately.

Centimeter millimeter centimeter micron diameter decimeter

57. In the absence of special requirements, the unit of the size number in the printed board wiring diagram is (B).

Centimeter millimeter centimeter micron diameter decimeter

58. The ratio of transformer capacity running in parallel is generally not more than (c).

A. 1: 1 b . 2: 1 c . 3: 1d . 4: 1

59. In order to prevent tap-changer failure, tap-changer joint resistance should be measured, and the difference is less than (d).

A.0.5% B. 1%

60. Under normal circumstances, in order to prevent the insulating oil from being excessively oxidized, the upper oil temperature should not exceed (B )℃.

A.75 B. 85 C. 95 D. 105

After the 6 1. transformer is put into operation, its insulation life can reach (b) years under the permitted conditions.

A.25 ~ 30 b . 20 ~ 25 c . 15 ~ 20d . 10 ~ 15

62. The voltage in the operation of the transformer should not exceed the rated voltage (C).

A.？ 2.0% B？ 2.5% C？ 5% D？ 10%

63.Y/ yn0 connected transformer, the current on the neutral line should not exceed (D )% of the rated current of the low-voltage winding.

A. 10 C. 15 D. 25

64. The transformer under the same load and cooling conditions, the oil temperature is higher than the usual (B )℃, should judge the transformer internal fault.

A.5 B. 10 C. 15 D. 20

65. When the power grid fails, if one transformer is damaged, the other transformers (C) will be overloaded.

A. not allowed B. allowed 2 hours C. allowed short time D. allowed 1 hour

66. The transformer core is made of thin silicon steel sheets insulated from each other, and its main purpose is to reduce (c).

A. stray loss B. copper loss C. eddy current loss D. hysteresis loss

67. When the transformers run in parallel, the ratio difference is less than (b).

A.？ 0.2% B？ 0.5% C？ 1% D？ 1.5%

68. The short-circuit voltage in power transformer is generally rated voltage (B).

A.2% ~ 4% b . 5% ~ 10% c . 1 1% ~ 15% d . 15% ~ 20%

69. In the power system? Kwh? As the unit of measurement of (b)

A. voltage b, electric energy c, electric power d potential

70. When the reference point changes, the potential difference in the circuit is (C).

A. Larger B. Smaller C. Constant D. Uncertain

7 1. The actual power supply voltage will decrease with the decrease of load current (b).

A. lower B. higher C. constant D. slightly lower

72. The frequency of China alternating current is 50Hz, and the period is (b) seconds.

a 0.0 1 b 0.02 c 0. 1d 0.2

73. The circuit consists of four parts (A) and switches.

A. power supply, load and connecting wires B. generators, motors and buses C. generators, loads and overhead lines

D. motors, bulbs and connecting wires

74. The reference point, also called zero, consists of (a).

A. artificial designation B. determined by the reference direction C. determined by the actual direction of potential D. determined by the nature of the earth

75, coil magnetic field direction judgment method is (b).

A. Right-handed rule of straight conductor B. Right-handed rule of spiral tube C. Left-handed rule D. Right-handed generator rule

76, the amplitude of sinusoidal alternating current is (b).

A. twice the maximum value of sinusoidal alternating current B. maximum value of sinusoidal alternating current C. sum of positive and negative waveforms of sinusoidal alternating current

D times the maximum value of sinusoidal alternating current.

77. When the moving conductor cuts the magnetic field lines to produce the maximum electromotive force, the included angle between the conductor and the magnetic field lines should be (D).

Answer. 0? B. 30？ C. 45？ D. 90？

78. Star connection, the common point of three-phase power supply is called (A) of three-phase power supply.

A. Neutral point B. Reference point C. Zero potential point D. Grounding point

79. The inductance coil is connected to an alternating current circuit with f=50Hz, and the inductance XL=50? , if connected to the power supply of f= 150Hz, the inductance XL is (a)?

150

80. The inductance coil is connected to an alternating current circuit with f=50Hz, and the inductance XL=50? , if connected to the power supply of f= 10Hz, the inductance XL is (c)?

A. 150 B. 250 C. 10 D. 60