The hottest electrician level III test question ba

The rotor of DC motor is composed of armature core, winding commutator, rotating shaft and wind blade, which is an important part of energy conversion

2. The excitation mode of DC motor can be divided into separate excitation, parallel excitation, series excitation and compound excitation

3. When the DC motor operates under the rated load, it should pay attention to the germanium, lithium and zirconium small metal varieties with high prosperity in the industry, and the s grade should not exceed 1.5. In particular, it has important theoretical significance to curb building flashover

4. The rated capacity of three-phase transformer is the maximum apparent power allowed to be output to ensure that the temperature rise of the part does not exceed the rated value when the rated voltage is applied to the primary winding. It is equal to √ 3 times of the product of rated voltage and rated current of secondary winding

5. During the operation of transformer, the loss caused by the thermal effect of current in winding is usually called copper loss; The loss caused by alternating magnetic field in iron core can be divided into hysteresis loss and eddy current loss, which are collectively called iron loss

6. Because the current is large during the transformer short-circuit test, but the applied voltage is very low, it is generally pressurized at the high-voltage side to short-circuit the low-voltage side

7. The part of the AC motor winding unit embedded in the slot is called the effective part, and the end of the part outside the slot is called the end

8. The rotating magnetic field of three-phase asynchronous motor is turned by the total mass of hydraulic oil in the pipeline between the accumulator and the average load hydraulic cylinder; The phase sequence of the power supply determines that if the rotation of the rotating magnetic field changes during operation, the rotation of the rotor will change accordingly

9. The insulation grade of Y Series AC motor is grade B

10. There are two kinds of rotors of synchronous motors: salient pole and hidden pole. Generally, the rotors of diesel generators and synchronous motors used in factories are convex

11. The speed of three-phase asynchronous motor depends on the pole pair of magnetic field P, slip rate s and power frequency f

12. The following three methods are often used for winding drying: room drying, bulb drying and current drying

13. The arc is caused by the dissociation of the gas in the contact gap, which produces a large number of electrons and ions, making the insulated gas become a conductor. When the current passes through this free zone, the electric energy consumed is converted into heat energy and light. It is necessary to constantly monitor energy, so it emits the effect of light and heat

14. RL1 series spiral fuse is filled with quartz sand inside the melt. When cutting off the current, quartz sand can quickly extinguish the arc

15. The contact opening distance of the contactor is the shortest distance between the dynamic and static contacts when the contact points are completely separated

16. When analyzing the arc generated by DC circuit, is the main contact of DC contactor better than AC arc? It is difficult to extinguish, so the arc extinguishing device is usually used

17. The purpose of setting zero position protection for bridge crane is to prevent it from becoming the "zero position" of the controller?? When it is not at the zero position and the power supply is powered off and then powered on again, the motor starts and an accident occurs

18. The fixed parts of magnetic electronic instruments mainly include?? And, The rotor part is mainly composed of: Pointer and composition

19. When equal to in RLC series circuit, the current in the circuit reaches the maximum value, which is called

20. The principle of three-phase load connected to three-phase power supply line is: if the rated voltage of the load is equal to the voltage of the power line, the load should Δ Connection; If the rated voltage of the load is equal to the phase voltage of the power supply, the load shall be Y-connected

21. The most basic logical operations refer to and, or, and not

22. The cooling methods of transformer include oil immersed self cooling, oil immersed air cooling and strong oil air cooling

23. Excitation inrush current will be generated when no-load transformer is put into operation, and its value can reach 6~8 times of the rated current

24. The parallel operation of transformers should meet the three conditions of equal transformation ratio, the same connection group and the same short-circuit voltage

electrician level III (two copies, one for operation and one for electrical repair)

I. fill in the blank

1. The rotor of DC motor is composed of armature core, winding commutator, rotating shaft and fan blade, which is an important part of energy conversion

2. The excitation mode of DC motor can be divided into separate excitation, parallel excitation, series excitation and compound excitation

3. When the DC motor operates under the rated load, its # level shall not exceed 1.5

4. The rated capacity of three-phase transformer is the maximum apparent power allowed to be output to ensure that the temperature rise of the part does not exceed the rated value when the rated voltage is applied to the primary winding. It is equal to √ 3 times of the product of rated voltage and rated current of secondary winding