Maintenance electrician test questions - Solutions - Huaqiang Electronic Network
First, fill in the blanks
1. Schottky diode's _____ switching time ______ is short, so the switching loss is much smaller than the ordinary diode.
2. Converting the binary number 1110 into a decimal number is ____14_________.
3. The horizontal scan signal generator in the oscilloscope generates the _____ sawtooth wave ______________.
4. The thermal component setting current of the thermal relay IFRN=__0.95~1.05__________IMN
5. When repairing the DC motor, it is necessary to carry out the withstand voltage test between the windings. The test voltage is _____ exchange ____
6. When the stepper motor is working, each time a _____ pulse signal ______ is input, the motor turns over an angle or goes further.
7. At the end of the overhaul, it is necessary to check the wiring again and check it correctly. After the _____ commissioning _____ is passed to the overhaul equipment, the handover procedure of the maintenance equipment can be handled.
8. In the maintenance and repair of electrical lines, the ______ safety ______ operating procedure of the power switchgear must be followed.
9. In the overhaul, you must pay attention to check the _______ grounding resistance value _______ to ensure that the grounding system is in good condition.
10. The signal that the system output has a reaction to the system is called ______feedback_______.
11. _______END________ is the program end command of the programmable controller.
12. When presetting the function of the inverter, it must be performed in _____ programming mode _______.
13. ______ The digital signal input ______ interface can make the inverter work according to the digital signal command output from the numerical control device or plc.
14, Schottky diodes are suitable for voltage ______ not high ______, but also require fast, efficient circuits.
15. In order to improve the reliability of electrical equipment operation, the neutral point of the ______ transformer low-voltage side is closely connected with the _______ grounding pole. This grounding method is called working ground.
16. The ___ISO10000______ standard is a guide to quality management and quality system elements.
17. In the operation of the instructor, the _____security_______ education must be strengthened for the trainees.
18, stepping, on behalf of ______ step ________.
19. Uncontrollable two-terminal devices, which have the function of _______ rectification ________, but have no controllable function.
20. The integrator circuit consisting of an operational amplifier is like a ____ low-pass filter __________.
21. In the logical algebraic expression, the _________ minimal logical expression _____________ is unique.
22, measuring the resistance below 1 ohm should use DC _______ double arm bridge _________.
23. When the combination switch is used to start and stop the motor below 7KW, the rated current of the switch should be equal to ___3____ times the rated current of the motor.
24. For equipment that has been overhauled, ____________ does not allow __________ wires to have connectors when re-threading in the pipe.
25, the general requirements for the protection of the grounding resistance is _______4 ohms or less ________.
26. The A/D converter is a _______ modulus ________ converter.
27. CIMS is an abbreviation for ___________ Computer Integrated Manufacturing System ____________.
28. The computer consists of CPU, memory and _____ input and output device ____.
29. When the programmable controller inputs the command, the programmer can be used to write the program, which is based on the ________ ladder diagram and the instruction list ____________.
30. In the F20 system, the command mnemonic for the normally open contact of the PLC and the busbar is ________LD________.
31. The inverter consists of the _______ main circuit _______ and the control circuit.
32. The output of the inverter is not allowed to connect to the _______ capacitor ____, nor is it allowed to connect a capacitive single-phase motor.
33. The object controlled by the numerical control system is _________ servo drive ______________.
34. In the numerical control machine tool, the positive direction of the coordinate axes X, Y and Z of the linear motion of the machine tool is defined as the _____ machine tool ______ coordinate system.
35. A device that converts a constant voltage in a DC power source into an adjustable DC voltage is called a __________ inverter ___________.
36. ________ Protective Earthing __________ is applicable to electrical equipment where the power neutral is not directly grounded.
37. ISO is an abbreviation of _________ International Organization for Standardization ___________.
38. When operating the transistor characteristic diagram, pay special attention to the step selection of the power consumption voltage and the ____ polarity_____ selection switch.
39. After the inverter fault trips, if you want to return to normal state, you should press ___RESET_____.
40, ______ electric shock ________ is the most serious electric shock accident.
41. _______ Two-phase electric shock ________ is the most dangerous form of electric shock.
42. Practice has proved that the low-frequency current is more harmful to the human body than the high-frequency current ____.
43. The capacity of the single-phase rectifier transformer can be calculated by _______P2=U2I2________.
44. When conducting theoretical training, it should be combined with the problems in the production technology and quality of the enterprise, ____ occupation ____, and propose solutions.
45. In order to improve the utilization of the power supply, appropriate reactive power compensation equipment should be connected in parallel in the inductive load circuit to improve the power factor.
46. A resolver is a signal component whose output voltage changes as the rotor angle changes.
47 According to the process requirements, in the electrical overhaul, the main power supply must be cut off first, and preventive safety measures should be taken.
48. The thermoelectric potential of the thermocouple output gradually rises from zero. After reaching the corresponding temperature, it no longer rises and presents a platform value.
49. Guiding operational training is an extremely important way and means to develop and improve the independent operational skills of the students.
50. The purpose of theoretical training is to enable the trainees to master the technical theoretical knowledge of the maintenance electrician's level through classroom teaching methods.
51 multivibrator, also known as unsteady circuit.
52. Temperature measurement with a fast thermocouple is a dynamic temperature measurement.
53. In the logic operation, A+AB= A.
54. The numerical control device is the core of the numerical control system, and its components include numerical control hardware and software.
55. The characteristics of the power field effect transistor are as follows: The static internal resistance of the gate is high, the driving power is small, and the gate signal can be automatically turned off after the gate signal is removed, and there is no secondary breakdown, and the safe working area is wide.
56. In the guidance operation and independent operation training, care should be taken to allow the students to repeatedly conduct the actual practice training.
57. Compared with ordinary rectifier diodes, Schottky diodes have a short reverse recovery time and a high operating frequency.
58. The op amp is basically composed of a high input impedance differential amplifier, a high gain voltage amplifier, and a low impedance output amplifier.
59. Digital multimeters now typically use LED displays.
60. The maintenance electrician team is mainly for production services.
61. Through the guidance operation, the students' hands-on operation ability is continuously enhanced and improved, and the operation skills are mastered.
Multiple choice questions:
1. The waveform observed on the oscilloscope is done by (B).
A, filament voltage B, deflection system C, accelerating voltage D, focusing voltage
2. The thermal element of the thermal relay sets the current IFRN = (A) IMN.
A, 0.95 to 1.05 B, 1 to 2 C, 0.8 to D, 1 to
3. In traction machinery (such as trams, mechanical vehicles, battery vehicles), and large rolling mills, DC motors are generally used instead of asynchronous motors because of the asynchronous motor (B).
A, power factor is low B, speed regulation performance is very poor C, starting torque is small D, starting current is too large
4. The standard linear induction synchronizer is the most widely used in practice, and its length is (D).
A, 100mm B, 1cm C, 1m D, 250mm
5. The main part of the thermometer consists of A/D converter, (B) series MCU minimum system and man-machine dialogue channel.
A, Z80 B, MCS-51 C, 32-bit D, 16-bit
6. The function of repeated grounding is to reduce the ground voltage of the leakage device casing and reduce the risk of (C) disconnection.
A, ground wire B, phase line C, neutral line D, equipment
7. The meter that can measure the DC power without distinguishing the polarity of the test leads is (B).
A, magnetoelectric system B, electromagnetic system C, electrostatic system D, electric system
8. In the operation of the maintenance electrician, pay special attention to (B) problems.
A, wear safety equipment B, prevention of safety accidents
C, live operation D, safe and civilized production behavior
9. The (B) output of the thermocouple is a platform value that rises from zero to the corresponding temperature and no longer rises.
A, resistance value B, thermoelectric potential C, voltage value D, impedance value
10. (D) Regularly control the on/off of the main switch in the inverter to obtain a three-phase output of any frequency.
A, chopper B, inverter
C, the control circuit D in the inverter, the inverter in the inverter
11. When repairing or replacing the main circuit ammeter, the maintenance electrician can remove the current meter from the current transformer secondary circuit (B).
A, disconnect B, short circuit C, do not process D, cut fuse
12. When measuring a triode with a transistor plotter, adjustment (C) can change the spacing between the family of characteristic curves.
A, step selection B, power consumption resistance
C, collector - base current / potential D, peak range
13. When filtering the transformer oil, first check that the oil filter is in good condition, and (B), the fire filter is strictly prohibited on the site.
A, connect the power supply B, connect the ground wire C, do insulation protection D, power off operation
14. The electrical control circuit design should maximize the need for (D).
A, voltage B, current C, power D, mechanical equipment processing technology.
15. In the repair work, it is necessary to repair according to the equipment (A), strictly control the quality of the repair, and must not reduce the original performance of the equipment.
A, raw data and accuracy requirements B, damage level
C, operation situation D, maintenance process requirements
16. When measuring the rolling force of a rolling mill, (.B) is usually selected as the sensor.
A, pressure sensor B, pressure magnetic sensor
C, Hall sensor D, piezoelectric sensor
17. The output of the frequency converter is not allowed to be connected ( C ).
A, pure resistance B, inductance C, capacitor D, motor
18. Where high stability of the transmission ratio is required, the (A) transmission method should be adopted.
A, gear B, belt C, chain D, worm gear
19. The most ideal working voltage for electrical equipment is its (C)
A, allowable voltage B, power supply voltage
C, rated voltage D, minimum voltage
20. After the inverter trips after the fault occurs, press the (C) key first to return it to normal.
A, MOD B, PRG
C, RESET D, RUN
21. (A) is the most dangerous form of electric shock.
A, two-phase electric shock B, electric shock
C, step voltage electric shock D, single phase electric shock
22. Strengthening collaboration is the basic requirement of (D) professional ethics
A, obey the law B, justice
C, hardworking and thrifty D, solidarity and mutual assistance
23. Through (D), the students' ability to work can be continuously enhanced and improved, so that they can master the operation skills.
A, demonstration operation B, safety education
C, on-site technical guidance D, guiding operation
24. The speed adjustment accuracy and range of the speed sensorless adjustment system is currently (C) a vector control system with a speed sensor. #p#分页头#e#
A, more than B, equivalent
C, lower than D, far below
25. Normally (B) between the inverter and the motor is connected to the contactor.
A, allow B, not allowed
C, need D, no need
26. The thermometer consists of two parts, part (A) and the main part.
A, probe B, thermocouple
C, thermistor D, sensor
27. (B) is a production site logistics control system.
A, production synchronization B, kanban management
C, quality management D, production equalization
28. When measuring the size of the inductor, (C) should be used.
A, DC single arm bridge B, DC double arm bridge
C, AC bridge D, multimeter
29. B2010 type planer V55 system, when the motor is lower than the rated speed, adopt (C) mode to adjust the speed.
A, constant power B, constant torque
C, constant torque D, weak magnetic
30. When the center distance between the two shafts is large, the (B) transmission method is generally used.
A, gear B, belt
C, fixed transmission ratio D, worm gear
31. When the person is exposed to electricity (A), artificial respiration should be performed.
A, there is no heartbeat, no breathing, no breathing, no heartbeat
C, neither heartbeat nor breathing D, both heartbeat and breathing
32. The basic principle of socialist professional ethics is (C).
A. Communism B, groupism
C. Collectivism D, serving the people wholeheartedly 3. Judging questions (N)1. The integrated op amp input stage uses a basic amplifying circuit.
The (Y)2.555 precision timer can be applied to pulse position adjustment.
(N)3. The basic waveforms of electronic display devices such as televisions and oscilloscopes are rectangular waves and sawtooth waves.
(N)4. A fuse must be added to the secondary circuit of the current transformer.
(N)5. In a static differential speed control system, the influence of disturbance on the output can be fully compensated.
(N)6. The main circuit of the inverter, including the rectifier, the intermediate DC link, the inverter, and the chopper.
(Y)7. The control object of the numerical control system is the servo drive device.
(N)8. The resistance at the output of the integrating op amp should be in parallel with the capacitor.
(N)9. The "AND" and "OR gate" in the logic circuit are opposite. The so-called "positive and gate" is "negative or gate", and the "positive or gate" is "negative and gate."
(N)10. The waveform observed on the oscilloscope is done by the accelerating voltage.
(Y)11. In the secondary circuit of the voltage transformer, a fuse must be added.
(N)12. When the motor is lower than the rated speed, the speed is regulated by constant speed.
(N)13. When the open-loop automatic control system is deviated, it can be adjusted automatically.
(Y)14. After the inverter fault trips, to return it to normal, press the RESET button.
(Y)15. According to the composition of the numerical control device, the numerical control system includes two parts: numerical control software and hardware.
(Y)16. In the three-phase half-controlled bridge rectifier circuit, the withstand voltage value of the thyristor is twice as large as the voltage of the secondary side of the transformer.
(N)17. The capacitor's discharge circuit must be equipped with a fuse.
(Y)18. The basic integral op amp consists of a resistor connected to the inverting input and a capacitor from the output to the inverting input.
The (Y)19.555 precision timer can be applied to pulse generators.
(Y)20. Motor "sickness" operation is an important cause of motor damage.
(N)21. The OUT command is an instruction to drive the coil to drive various relays.
(Y) 22. The withstand voltage of the thyristor in the three-phase half-controlled bridge rectifier circuit is twice the effective value of the secondary voltage of the transformer.
(N)23. When the transistor is used as a switch, it should work in an amplified state.
(Y)24, the core of the transformer must be grounded at one point.
(N)25, the contactor is generally required to be connected between the inverter and the motor.
(N)26, the direction of the moiré fringe is the same as the direction of the grating reticle.
(N)27, a thyristor inverter is a device that converts alternating current electrical energy into direct current electrical energy.
(N)28, the output of the inverter is not allowed to connect to the inductor.
(Y)29. In the power distribution cabinet, the terminal is generally placed on the leftmost and lowermost sides.
(N)30. Sudden power outages will generate a large amount of waste products, a large number of production cuts, and a power load that causes a large loss in the economy, which is a “secondary loadâ€.
(Y) 31. Establishing a correct outlook on life is a prerequisite for professional ethics.
(Y)32, for the 35KV cable entry section, it is required to install a discharge gap at the connection between the cable and the overhead line.
(Y) 33. Professional ethics is the ideological basis for people to abide by professional discipline.
Fourth, short answer questions
1. What is the “crawling†of the motor, how to debug?
Answer: When the given voltage is zero, the motor speed should be zero. If it is not zero, it is called the crawling of the motor. Adjust the zero potentiometer R31 on the A2 board to make the motor speed zero. Then increase the given voltage, then the motor speed increases. When the given voltage is changed positive or negative and the motor turns to change, the debugging is normal.
2. What are the main instructions of CNC machine tools?
A: Preparation function G command; feed function F command; spindle speed S command; tool function T command; auxiliary function M command.
3. IMN=17.5A of cage asynchronous motor, when the “single infrequent start or stop, long-term workâ€, and “single start or stop, long-term workâ€, how much melt current should be ?
Answer: 1. Single station does not start or stop frequently, and long-term work IFUN=(1.5~2.5)IMN=(26.25~43.75)A
2, a single start or stop frequently, and long-term work IFUN = (3 ~ 3.5) IMN = (52.5 ~ 61.25) A
4. As shown in the figure, which CNC system is used, what features are seen from the figure.
A: It is a single-axis semi-closed loop numerical control system. It has high stability and is a system commonly used in CNC machine tools. It is characterized by adding an encoder to the servo motor and detecting the rotation angle of the servo motor. Detect the displacement of the moving part, and then feed back to the numerical control device to participate in the adjustment.
5. What are the precautions for the installation of the inverter wiring?
Answer: 1. Connect the low-voltage circuit breaker and contactor between the power supply and the inverter to protect the inverter and facilitate installation and maintenance; 2. The contactor is generally not allowed between the inverter and the motor; 3. The inverter is generally No need to connect the thermal relay; 4, the output side of the inverter is not allowed to connect capacitors and capacitive single-phase motors.
6. Calculation problem: When designing the instantaneous tripping setting current of the motor electromagnetic release, it is known that In=12.4A, Ist/In=5.5, and the maximum and minimum values ​​of the setting current are obtained.
Answer: Because I≥KIST where K is 1~7, the maximum value is IM=7IST=7×5.5In=7×5.5×12.4=477.4A The minimum value is IM=IST=5.5In=5.5×12.4=68.2A
7. Briefly describe the characteristics of industrial television testing.
Answer: 1. There is no mechanical connection between the detection object and the industrial TV camera. Multiple cameras can be used to obtain spatial information. 2. A large amount of information can be read in a short time. 3. A useful characteristic signal can be extracted from the video. A certain way is converted into an electrical signal for use as an operation, detection, and control.
8. What are the components of the external interface circuit of the inverter?
Answer: 1. Multi-function input terminal and output contact; 2. Multi-function analog input/output signal contact; 3. Digital signal input/output contact; 4. Communication interface.
9. When reading the technical specifications of the CNC machine tool, after analyzing each part of the circuit, what overall inspection and mapping is required to understand the overall content of the control system.
A: Also check the entire control line to see if there are any omissions. In particular, we should further examine and understand the relationship between the various control links from the overall perspective, so as to fully understand the role, working process and main parameters of each part of the schematic. purpose.
10. When the microcomputer thermometer performs temperature dynamic sampling, what is the specific scheme for the platform value?
A: First, find the average of several sample values, and then find the deviation of each sample value from the average value to get the maximum deviation value. It is judged whether the maximum deviation value is smaller than a given error range, and if the difference is over, the sample value corresponding to the maximum deviation value is discarded, and the average value of the remaining sample values ​​is the platform value.
11. AC motor relay contactor circuit design includes the basic content.
Answer: 1. Determine the current type and voltage quantity of the control circuit; 2. Control the main circuit control mode and its protection link for motor starting, forward and reverse rotation, braking and shifting; 3. Control circuit, execution circuit and chain protection link Auxiliary circuit design such as signal display and safety lighting.
12. What are the requirements for position detection devices for CNC machine tools?
Answer: The requirements of the CNC machine tool for the detection device are: high reliability and anti-interference ability; meet the requirements of machine tool processing precision and processing speed; easy to use and maintain; low cost.
13. What are the characteristics of the gear transmission.
Answer: 1. High efficiency; 2. Compact structure and small size; 3. Reliable work and long service life; 4. Stable transmission ratio; 5. High manufacturing and installation accuracy and high price; 6. Unsuitable for occasions where the transmission distance is too large. use.
14. In the automatic estimation and processing system of production information, what work is mainly done by the upper computer.
A: Collection and storage of processing quality information, formation of management files, monitoring of subordinate computer actions; monitoring of control quality.
Five, essay questions
1. Start three motors in the order of M1, M2, and M3, and stop in the order of M3, M2, and M1. Design an electrical schematic controlled by buttons.
2. As shown in the figure, for the ladder diagram of a device sequence control, please write its program statement.
3. Three motors M1, M2, M3, when M1 starts time t1, M2 starts, then M3 starts after time t2; M3 stops first when stop, M2 stops after time t3, and M1 stops after time t4. Please design an electrical control schematic.
answer:
4. As shown in the figure, the ladder diagram of multi-segment speed control, write its program statement.
(figure omitted)
5. Discuss the meaning of career choice.
6. Discuss the necessity of strengthening professional ethics
7. Analytical method for electrical faults in hydraulic systems.
Answer: 1) In many cases, you can try to analyze the hydraulic system by analyzing the electrical system.
2) Make full use of the maintenance knowledge and experience of the electrical system to help repair the hydraulic system failure
3) Find external anomalies, comprehensively analyze the internal laws of faults, and master the correct methods to detect faults. #p#分页头#e#
8. The basic structure and keyboard configuration of the inverter.
Answer: The inverter consists of the main circuit and the control circuit. The main circuit includes: a rectifier, an intermediate DC link, and an inverter.
The keyboard configuration includes: mode conversion key, increase/decrease key, read/write key, operation operation key, reset key, number key.
9. Self-diagnosis function and alarm processing method of CNC system A: 1. Power-on self-test: When the CNC system is powered on, the system internal self-diagnosis software detects the key hardware and control software in the system one by one. Once the test passes, an alarm message is displayed on the CRT to indicate the fault location. Only after all passes can the normal operation ready state be entered. A power-on self test typically locates a fault on a circuit or module or even a chip. But sometimes you need to check and judge further to find the cause of the problem and eliminate it. 2. Real-time self-diagnosis: The CNC system performs automatic test and inspection on the internal system, servo system, I/O interface and other external devices of the numerical control device at any time during normal operation, and displays relevant status information. If a problem is detected, the alarm number and the alarm content are immediately displayed, and whether the action is stopped or stopped automatically is determined according to the nature of the fault. During the inspection, the maintenance personnel can further diagnose and eliminate the fault according to the alarm content and the NC internal key flag register and the operating unit status of the PLC displayed when appropriate. 3. After the fault is removed, the alarm will not be automatically eliminated. According to different alarms, you need to press the “RESET†or “STOP†button to eliminate, or need to reset the power supply, shut down and restart, to restore the system operation.
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