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2019 basic knowledge point test of electrical engineer "power transmission and transformation" (14)

[Abstract] the 2019 electrical engineer examination has entered the preparation stage, and universal school has sorted out the "basic knowledge point test of 2019 electrical engineer" power transmission and transformation ", hope 1. General parts: pull bowl is expected to help you consolidate the basic knowledge points of candidates, please pay attention to the universal school electrical engineer examination channel for more preparation information

1. The accuracy grade of electrical instruments is expressed by the maximum (c) error of the instrument

a. relative

b. absolute

c. quotation

d. additional

2. The relationship between the average value of the forward current flowing through the diode and the average value of the current flowing through the load in the single-phase half wave rectifier circuit is (a)

a. both are equal

b. the former is smaller than the latter

c. the former is greater than the latter

d. the former is equal to 1/2 of the latter

3. The two terminals (d) of the magnetoelectric microammeter should be connected after use

a. open circuit

b. grounding

c. shell connection

d. short circuit with wires

4. The ratio of turns of the primary and secondary windings of a transformer is equal to 25. If the rated voltage on the secondary side is 400V, the rated voltage on the primary side is (a)

a.10000v;

b.20000v;

c.6000v;

d.3300v。

5. In the AC file of an ordinary multimeter, the measurement mechanism reflects (b)

a. effective value, and the calibration is also based on the effective value

b. average value, the calibration is based on the effective value of sine wave

c. average value, and the calibration is also based on the average value

d. peak value, and the calibration is also based on the peak value

6. In the high-voltage insulation test, it is required that the pulsation factor of the DC test voltage under the output working current should not be greater than (b)

a.1%;

b.3%;

c.5%;

d.10%。

7. When the ball spacing is not greater than the ball radius, the commonly used measurement ball gap is a typical (b) electric field gap

a. uniform

b. slightly uneven

c. uneven

d. extremely uneven

8. Among the following items that characterize the physical and chemical properties of SF6 gas, (c) is wrong

a. colorless and tasteless

b. odorless and non-toxic

c. combustible

d. inert gas with stable chemical properties

9. In the no-load test of transformer, the relationship between the calculated value of rated no-load loss P0 and no-load current I0 and the ratio of transformer rated voltage UN to test applied voltage U0 (U is comparable to a 1600t shuttle double station press in the R & D center of bentler Sigri in ried im innkreis, n/u0). In the following descriptions, item (d) is the most accurate (among which, the value range of U0 is 0.1 ~ 1.05 times UN)

a.p0 and I0 are proportional to (un/u0)

b.p0 is proportional to (un/u0); I0 is proportional to (un/u0)

c.p0 is proportional to (un/u0) n; I0 is proportional to (un/u0) m, and n=1.9 ~ 2.0; Carry out the loading experiment at a constant rate, m=1 ~ 2

d. when (un/u0) =1.0, the calculated values of P0 and I0 are equal to the measured values of the test

10. Among the parameters of transformer load loss and no-load loss measurement, the influence of test power frequency on parameter (c) can be ignored

a. no load loss and no load current

b. load loss and short-circuit impedance

c. resistance component of winding resistance loss and short-circuit impedance

d. reactance component of additional loss and short-circuit impedance

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