Maintenance electrician test questions (1) Maintenance electrician test questions
Fill in the blanks
1, the switching time of Schottky diode is short, so the switching loss is much smaller than that of ordinary diode.
2. The binary number110 is _ _ _ _ _.
3. The horizontal scanning signal generator in the oscilloscope generates _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
4. The setting current of thermal element of thermal relay IFRN = _ _ 0.95 ~1.05 _ _ _ _ _ _ IMN.
5, in the maintenance of DC motor, to withstand voltage test between windings, the test voltage is _ _ _ _ _ _ _ _ AC.
6. When the stepping motor is working, every time a _ _ _ _ _ pulse signal is input, the motor will turn an angle or take a step forward.
7, after the overhaul, but also to check the wiring again, check and correct, and overhaul equipment for _ _ _ _ _ _ qualified, to handle the handover procedures of maintenance equipment.
8, in the maintenance of electrical wiring, must follow the principle of _ _ _ _ _ _ _ _ _ _.
9, maintenance must pay attention to check the grounding resistance value of _ _ _ _ _ _ _ _ _ _ _ _ _, to ensure that the grounding system is in good condition.
10, the signal that the system outputs and reacts on this system is called _ _ _ _ _ _ _ feedback _ _ _.
1 1 and _ _ _ _ _ _ END _ _ _ _ _ are the program end instructions of the programmable controller.
12, inverter function preset, must be in _ _ _ _ _ _ _ _ _ _.
13, _ _ _ _ _ _ digital signal input _ _ _ interface, which can make the frequency converter work according to the digital signal instruction output by numerical control equipment or PLC.
14, Schottky diode is suitable for _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
15. In order to improve the reliability of electrical equipment operation, the neutral point on the low-voltage side of _ _ _ _ transformer is closely connected with _ _ _ _ grounding electrode. This grounding method is called working grounding.
Standards 16, _ _ ISO10000 _ _ _ _ are guidelines for quality management and quality system elements.
17. When instructing students to operate, we should always strengthen the education of _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
18, step by step, which stands for _ _ _ _ _ _ _ _ _.
19, uncontrollable two-terminal device, which has the function of _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
20. The integrator circuit composed of operational amplifiers is like a _ _ _ _ _ _ low-pass filter in performance.
2 1. Among the logical algebraic expressions, the simplest logical expression _ _ _ _ _ _ _ is unique.
22, measuring resistance below 65438 0 ohms should choose DC _ _ _ _ _ _ _ _ _ _.
23, when using the combination switch to start and stop the motor below 7KW, the rated current of the switch should be equal to _ _ _ _ times the rated current of the motor.
24, equipment maintenance, threading in the tube again, _ _ _ _ _ _ _ _ _ _ _ _ _ _ wires are not allowed to have joints.
25. It is generally required to protect the grounding resistance of _ _ _ _ _ _ _ _ below 4 ohms.
26. The A/D converter is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
27.CIMS stands for _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
28. The computer is composed of CPU, memory and _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
29, programmable controller input instructions, you can use the programmer to write programs, is based on _ _ _ _ _ _ ladder diagram and instruction table _ _ _ _ _.
30. In the F20 system, the instruction mnemonic of the normally open contact of PLC connected to the bus is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
3 1, frequency converter is composed of _ _ _ _ _ _ main circuit and control circuit.
32, the output of the inverter is not allowed to connect _ _ _ _ _ _ _ capacitor _ _ _ _ _ _ _, and it is not allowed to connect capacitive single-phase motor.
33. The object of numerical control system control is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ system.
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 _ _ _ _ _ _ coordinate system of the machine tool.
35. The device that converts the constant voltage in DC power supply into adjustable DC voltage is called _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
36._ _ _ _ _ _ _ _ Protective grounding _ _ _ _ _ _ is applicable to electrical equipment whose power neutral line is not directly grounded.
37.ISO stands for _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
38. When operating the transistor characteristic plotter, special attention should be paid to the ladder selection of power consumption voltage and the _ _ _ _ _ polarity selection switch.
39, inverter fault trip, to make it back to normal, should press _ _ _ _ _ _ _.
40. _ _ _ _ _ _ Electric shock is the most serious electric shock accident.
4 1 and _ _ _ _ _ two-phase electric shock _ _ _ _ is the most dangerous form of electric shock.
42. Practice has proved that low-frequency current is more harmful to human body than high-frequency current.
43. The capacity of single-phase rectifier transformer can be calculated by _ _ _ _ p2 = U2I2 _ _ _ _ _.
44, theoretical training, should be combined with the enterprise, the professional production of _ _ _ _ _ _ _ technology, quality problems are analyzed, and put forward solutions.
45. In order to improve the utilization rate of power supply, appropriate reactive power compensation equipment should be connected in parallel in the inductive load circuit to improve the power factor.
46. The resolver is a signal element, and its output voltage varies with the rotor angle.
According to the technological requirements, the main power supply should be cut off and preventive safety measures should be taken during electrical maintenance.
48. Thermocouple output thermoelectric potential, gradually rising from zero, after reaching the corresponding temperature, no longer rising, showing a platform value.
49. Guiding operation training is an extremely important way and means to cultivate and improve students' independent operation skills.
50. The purpose of theoretical training is to enable students to master the technical and theoretical knowledge of maintenance electrician through classroom teaching.
5 1 multivibrator, also known as unstable circuit.
52. Using fast thermocouple to measure temperature belongs to dynamic temperature measurement.
53. In logical 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 power field effect transistor has the characteristics of high static internal resistance of the gate, low driving power, automatic turn-off after removing the gate signal, no secondary breakdown and wide safe working area.
56. In guiding operation and independent operation training, students should be paid attention to repeatedly carrying out the opposite practical operation training.
57. Schottky diode compared with ordinary rectifier diode, reverse recovery time is short, high working frequency.
58. Operational amplifiers are basically composed of high input impedance differential amplifiers, high gain voltage amplifiers and low impedance output amplifiers.
59. Now digital multimeter generally uses LED display screen.
60. The maintenance electrician team mainly serves production.
6 1. Through guiding operation, students' hands-on operation ability is constantly enhanced and improved, and they are proficient in operation skills.
Multiple choice question:
1. The waveform observed on the oscilloscope is completed by (b).
Filament voltage b, deflection system c, accelerating electrode voltage d and focusing electrode voltage.
2. Setting current of thermal element of thermal relay IFRN=( A )IMN.
a、0.95~ 1.05 B、 1~2 C、0.8~ D、 1~
3. In traction machinery (such as trams, mechanical cars, battery cars) and large-scale rolling mills, DC motors are generally used to replace asynchronous motors because of (B) of asynchronous motors.
A, low power factor b, poor speed regulation performance c, small starting torque d and excessive starting current.
4. The standard linear inductosyn is the most widely used in practice, and the length of each block is (D).
A, 1 00mm b, 1 cm c,1m d, 250mm.
5. The host part of the thermometer is composed of A/D converter, (b) series single chip microcomputer minimum system and man-machine dialogue channel.
A, Z80 B, MCS-5 1c, 32-bit d, 16.
6. The role of repeated grounding is to reduce the grounding voltage of the leakage equipment shell and reduce the risk of (c) disconnection.
A, ground wire b, phase wire c, zero wire d, equipment
7. Don't need to distinguish the polarity of the pen, can measure the dc power meter is (b).
A, magnetoelectric system B, electromagnetic system C, electrostatic system D, electrical system
8. Maintenance electricians should pay special attention to problem (b) in operation.
A. Wear safety protection articles B. Prevent safety accidents
C, live working D, safe and civilized production behavior
9. The output of thermocouple (B) is a stable value after gradually rising from zero to the corresponding temperature.
A, resistance value b, thermoelectric potential c, voltage value d and impedance value
10.(d) Regularly control the on-off of the main switch in the inverter to obtain three-phase output with any frequency.
A, chopper b, frequency converter
C, control circuit d in frequency converter, inverter in frequency converter
1 1. When repairing or replacing the ammeter in the main circuit, the maintenance electrician will connect the secondary circuit of the current transformer (B) and then remove the ammeter.
A, disconnect B, short circuit C, leave D untreated, and cut the fuse.
12. When measuring triode with transistor plotter, adjusting (c) can change the spacing between characteristic curve families.
A, step selection B, power consumption resistance
C, collector-base current/potential d, peak range
13. When filtering transformer oil, first check whether the oil filter is in good condition. (b) Fireworks are strictly prohibited at the oil filter site.
A, connect the power supply B, connect the grounding wire C, do a good job in insulation protection D and power-off operation.
14. The design of electrical control circuit should meet the needs of (d) to the maximum extent.
A, voltage b, current c, power d, mechanical equipment processing technology.
15. In the repair work, repair should be carried out according to the equipment (A), and the repair quality should be strictly controlled, and the original performance of the equipment should not be reduced.
A, the original data and accuracy requirements B, the degree of damage
C, operation d, maintenance process requirements
16. When measuring the rolling force of the rolling mill. B) is usually selected as the sensor.
A, pressure sensor b, piezomagnetic sensor
C hall sensor d and piezoelectric sensor
17. The output of the frequency converter is not allowed to be connected (C).
A, pure resistance b, inductance c, capacitance d, motor
18. When the transmission ratio is required to be stable, the transmission mode (A) should be adopted.
A, gear b, belt c, chain d, worm wheel and worm.
19, the most ideal working voltage of electrical equipment is its (c).
A, allowable voltage b, power supply voltage
C, rated voltage d, minimum voltage
20, inverter fault trip, to make it back to normal state should press (c) first.
a、MOD B、PRG
C, reset d, run
2 1 and (a) are the most dangerous forms of electric shock.
A, two-phase electric shock B, electric shock
C, step voltage electric shock D, single-phase electric shock
22. Strengthening cooperation is the basic requirement of (d) professional ethics.
A, obey the law B, handle affairs fairly
C, thrift D, solidarity and mutual assistance
23. Through (d), students' practical ability can be continuously enhanced and improved, so as to master operational skills.
A, demonstration operation b, safety education
C, on-site technical guidance D, guiding operation
24. The speed adjustment accuracy and range of speed sensorless adjustment system are currently (c) vector control system with speed sensor.
A, greater than b, is equivalent to
C, lower than d, much lower than d.
25, frequency converter and motor are generally connected with (B) contactor.
A. Allow B. Not allow
C, need D, do not need
26, thermometer consists of two parts, namely (a) and the host part.
A, probe b, thermocouple
C, thermistor d, sensor
27, (b) is the production site logistics control system.
A, production synchronization B, Kanban management
C, quality management D, production equalization
28, measuring inductance size, should choose (c).
A, DC single-arm bridge B, DC double-arm bridge
Ac bridge d, multimeter
29, B20 10 gantry planer V55 system, when the motor speed is lower than the rated speed, adopt (c) mode speed regulation.
A, constant power b, constant torque
C, constant torque d, weak magnetism
30, when the center distance between the two shafts is large, generally choose (B) transmission mode.
Belt for gear a and gear b
C, constant transmission ratio d, worm wheel and worm
3 1, electric shock (a), artificial respiration should be carried out.
A, heartbeat does not breathe b, breathing does not beat.
C, no heartbeat and no breathing D, both heartbeat and breathing.
32, the basic principle of socialist professional ethics is (C).
A, * * * materialism B, collectivism
C, collectivism D, serving the people wholeheartedly
Third, the judgment question
(n) 1。 The input stage of integrated operational amplifier adopts basic amplification circuit.
(Y )2.555 precision timer can be used for pulse position adjustment.
(noun) 3. The basic waveforms of electronic display equipment such as TV and oscilloscope are rectangular wave and sawtooth wave.
(n) 4。 The secondary circuit of current transformer must be equipped with fuse.
(n) 5。 In the speed control system with static error, the influence of disturbance on output can be fully compensated.
(n) 6。 The main circuit of frequency converter includes rectifier, intermediate DC link, inverter and chopper.
(y) 7。 The control object of numerical control system is servo drive device.
(n) 8。 The resistor at the output of the integrating operational amplifier should be connected in parallel with the capacitor.
(n) 9。 The AND gate and OR gate in logic circuit are opposite, so-called positive AND gate is negative OR gate, and positive OR gate is negative AND gate.
10 ... The waveform observed on the oscilloscope is completed by accelerating the electrode voltage.
1 1。 +0. The secondary circuit of voltage transformer must be equipped with fuse.
(N) 12 ... When the motor is lower than the rated speed, the speed is adjusted by constant speed.
(N) 13 ... The open-loop automatic control system can automatically adjust when deviation occurs.
(Y) 14 ... If the inverter fails to trip, press the reset key to restore it to normal state.
(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 of the thyristor is several times that of the transformer secondary voltage.
(N) 17 ... The discharge circuit of the capacitor must be fused.
(Y) 18 ... The basic integrating operational amplifier consists of a resistor connected to the inverting input and a capacitor between the output and the inverting input.
(Y) 19.555 precision timer can be applied to pulse generator.
20-year-old .. Running the motor with illness is an important cause of motor damage.
(n) 2 1。 Out command is the command to drive the coil, which is used to drive various relays.
(Y )22 .. The withstand voltage of the thyristor in the three-phase semi-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 the amplification state.
(Y )24。 The iron core of the transformer must be grounded at one point.
(N )25。 Generally speaking, a contactor needs to be connected between the inverter and the motor.
(N )26。 The direction of moire fringe is the same as that of grating scribing.
(N )27。 Thyristor inverter is a device that converts AC power into DC power.
(N )28。 The output of the frequency converter is not allowed to be connected with inductance.
(Y )29 In the power distribution cabinet, the terminals are generally placed at the far left and the bottom.
Thirty years old. Sudden power failure will produce a lot of waste products, reduce output and cause great economic losses, which belongs to "secondary load".
(Y )3 1。 Establishing a correct outlook on life is the premise of cultivating professional ethics.
(Y )32。 When the 35KV cable enters the line segment, it is required to set a discharge gap at the connection between the cable and the overhead line.
(Y)33。 Professional ethics is the ideological basis for urging people to abide by professional discipline.
Fourth, short answer questions
1. What is motor "crawling" and how to debug it?
Answer: When the given voltage is zero, the motor speed should be zero. If it is not zero, it is called motor crawling. Adjust the zero potentiometer R3 1 on the A2 board to make the motor speed zero. Then increase the given voltage, and the motor speed will increase accordingly. If the given voltage changes and the motor steering changes, the debugging will be normal.
2. What are the main instruction codes of CNC machine tools?
Answer: Prepare the function G instruction; Feed function f instruction; Spindle speed s instruction; Tool function test instruction; Auxiliary function m instruction.
3. IMN of squirrel-cage asynchronous motor =17.5a. What should be the melt current for "long-term operation without frequent start and stop of single machine" and "long-term operation with frequent start and stop of single machine"?
Answer: 1, single machine does not start and stop frequently, and the working time is long. Ifun = (1.5 ~ 2.5) IMN = (26.25 ~ 43.75) a.
2. Single machine starts and stops frequently, with long working hours. ifun =(3 ~ 3.5)IMN =(52.5 ~ 6 1.25)a
4, as shown in the figure is what kind of numerical control system, what are the characteristics from the picture.
Answer: It is a single-axis semi-closed loop numerical control system with high stability. At present, it is widely used in CNC machine tools. It is characterized by installing an encoder on the servo motor, indirectly detecting the displacement of the moving parts by detecting the rotation angle of the servo motor, and then feeding back to the numerical control device for adjustment.
5. What are the precautions for the installation of inverter wiring?
Answer: 1. Connect low-voltage circuit breakers and contactors between power supply and inverter to protect inverter and facilitate installation and maintenance; 2. Contactors are generally not allowed to be connected between the frequency converter and the motor; 3. In general, the inverter does not need to be connected with a thermal relay; 4. Capacitors and capacitive single-phase motors are not allowed to be used at the output side of the frequency converter.
6. Calculation problem: When designing and selecting the instantaneous trip setting current of the motor electromagnetic trip, In= 12.4A and Ist/In=5.5 are known, so as to find the maximum and minimum values of the setting current.
Answer: Because I≥KIST, where k is 1~7, the maximum value is IM = 7 ist = 7× 5.5 in = 7× 5.5×12.4 = 477.4a, and the minimum value is IM = ist = 5.5 in = 5.5×1.
7. Briefly describe the characteristics of industrial TV detection.
Answer: 1. There is no mechanical connection between the test object and the industrial TV camera, so multiple cameras can be used to obtain spatial information; 2. You can read a lot of information in a short time; 3. Useful characteristic signals can be extracted from video and converted into electrical signals in a certain way for operation, detection and control.
8. What are the external interface circuits of the frequency converter?
Answer: 1, multi-function input terminal and output contact; 2. Multifunctional analog input/output signal contacts; 3. Digital signal input/output contacts; 4. Communication interface.
9. When reading the technical specification of CNC machine tools, after analyzing each local circuit, what overall inspection and mapping are needed to understand the overall content of the control system.
Answer: Also check the whole control circuit to see if there are any omissions. In particular, it is necessary to further check and understand the relationship between control links from the overall point of view, so as to fully understand the functions, working processes and main parameters of each part in the schematic diagram.
10. What is the specific scheme for calculating the platform value when the microcomputer thermometer samples the dynamic temperature?
Answer: First, find the average value of several sampling values, and then find the deviation between each sampling value and the average value to get the maximum deviation value. Judge whether the maximum deviation value is less than the given error range. If it exceeds the tolerance, discard the sampling value corresponding to the maximum deviation value and average the remaining sampling values to the platform value.
1 1. What are the basic contents of AC motor relay contactor circuit design?
Answer: 1. Determine the current type and voltage of the control circuit; 2. Design of control mode and protection link of main circuits such as motor starting, forward and reverse rotation, braking and speed change; 3. Design of auxiliary circuits such as control circuit, executive circuit, interlocking protection link, signal display and safety lighting.
12. What are the requirements of CNC machine tools for position detection devices?
Answer: The requirements of CNC machine tools for detection devices are: high reliability and strong anti-interference ability; Meet the requirements of machine tool machining accuracy and machining speed; Easy to use and maintain; Low cost.
13. What are the characteristics of gear transmission?
Answer: 1, with high efficiency; 2. Compact structure and small volume; 3. Reliable operation and long service life; 4. The transmission ratio is stable; 5, the manufacturing and installation accuracy is high and the price is expensive; 6. It should not be used in situations where the transmission distance is too large.
14. What is the main work of the upper computer in the automatic production information speculation and processing system?
Answer: the collection and storage of processing quality information, the formation of management documents, and the monitoring of the action of the lower computer; Control quality monitoring.
Verb (abbreviation of verb) On the Problems of Literature
1. The three motors shall be started in the order of M 1, M2 and M3, and stopped in the order of M3, M2 and M 1. Design the electrical schematic diagram of button control.
2. As shown in the figure, it is a ladder diagram of equipment sequence control. Please write its program statement.
3.M 1, M2 and M3 motors will be started by M2 when the starting time of M 1 passes t 1, and by M3 after t2; When stopping, M3 stops first, then t3, and then m 1 T4. Please design the schematic diagram of electrical control.
A:
4, as shown in the figure, multi-stage speed control ladder diagram, write its program statement.
(Figure omitted)
5. On the significance of career choice.
6. On the necessity of strengthening professional ethics.
7. Analysis method of electrical fault of hydraulic system.
Answer: 1) Many times we can try to analyze the hydraulic system by analyzing the electrical system.
2) Make full use of the knowledge and experience of electrical system maintenance, which is helpful to the maintenance of hydraulic system faults.
3) Find out the external anomalies, comprehensively analyze the internal laws of faults, and master the correct methods to find out the faults.
8. Basic structure and keyboard configuration of frequency converter.
Answer: The frequency converter consists of the main circuit and the control circuit. The main circuit includes rectifier, intermediate DC link and inverter.
The keyboard is equipped with: mode conversion key, increase and decrease key, read and write key, run operation key, reset key and numeric key.
9. Self-diagnosis function of numerical control system and alarm processing method
Answer: 1. Power-on self-inspection: After the CNC system is powered on, the self-diagnosis software inside the system tests the key hardware and control software in the system one by one. Once the test fails, an alarm message will be displayed on CRT, indicating the fault location. Only when all of them pass can they enter the normal operation preparation state. POST can usually locate the fault of a circuit or module or even a chip. But sometimes further inspection and judgment are needed to find the cause of the failure and eliminate it. 2. Real-time self-diagnosis: During the normal operation of the numerical control system, the internal components of the system, servo system, I/O interface and other external devices of the numerical control device are automatically detected and checked at any time, and relevant status information is displayed. If a problem is detected, it will immediately display the alarm number and alarm content, and automatically decide whether to stop the action or stop the machine 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, combined with the timely display of the key mark register in NC and the status of PLC operation unit. 3. After troubleshooting, the alarm is often not automatically eliminated. Depending on the alarm, you need to press the "reset" or "stop" key to eliminate it, or you need to reset the power supply and restart it to restore the system operation.