Maintenance Electrician Technician Test QuestionsMaintenance Electrician Technician Test Questions
I. Fill in the blanks
1, Schottky diode _____ switching time ______ is short, so the switching loss is much smaller than ordinary diodes.
2, binary number 1110 converted to decimal number is _______14 _________.
3, the oscilloscope in the horizontal scanning signal generator is generated _____ sawtooth wave ______________.
4, the thermal relay's thermal element rectification current IFRN = __0.95~1.05__________IMN
5, in the maintenance of DC motors, to carry out voltage withstand test between the windings, the test voltage is used to _____ AC____ electricity
6, the stepper motor work, each input _____ Pulse signal ______, the motor turns over an angle or step forward.
7, the end of the overhaul, but also again check the wiring, check for errors, and overhaul the equipment for _____ debugging _____ qualified before the handover of overhaul equipment procedures.
8, in the maintenance and overhaul of the electrical line, be sure to follow the ______ safety ______ operating procedures for power switchgear.
9, overhaul must pay attention to check the _______ grounding resistance value _______ to ensure that the grounding system is in perfect condition.
10, the output of the system to the system to produce the opposite effect of the signal is called ______ feedback _______.
11, _______END ________ is the program end instruction of the programmable controller.
12, the function preset for the inverter must be carried out in _____ programming mode __________.
13, ______ digital signal input ______ interface, you can make the inverter according to the digital signal instruction output by the numerical control equipment or PLC to work.
14, Schottky diode is suitable for voltage ______ not high ______, but also requires fast, efficient circuit.
15, in order to improve the reliability of the operation of electrical equipment, the ______ transformer low voltage side neutral point and _______ grounding pole closely connected, this grounding method is called work grounding.
16, ___ISO10000 ______ standard, is the quality management and quality system elements guide.
17, in guiding the operation of the trainee, the trainee must often strengthen the _____ safety _______ education.
18, stepping, stands for ______ stepping ________.
19, uncontrollable two-terminal device, which has _______ the role of rectification ________ but no controllable function.
20, An integrator circuit consisting of an operational amplifier, which is like a _______ low-pass filter __________ in performance.
21, The ____________ simplest logical expression _____________ is unique among logical algebraic expressions.
22, DC _______ two-arm bridge _________ should be used to measure resistances below 1 ohm.
23, in the selection of the combination switch to start, stop the motor under 7KW, the switch rated current should be equal to ___3 ____ times the rated current of the motor.
24, for overhaul of the equipment, in the pipe re-threading, _________ do not allow __________ wires with joints.
25, the general requirement for protective grounding resistance value of _______4 ohms below ________.
26, A/D converter is _______ analog-to-digital ________ converter.
27, CIMS is the abbreviation for ___________ Computer Integrated Manufacturing System ____________.
28, A computer consists of a CPU, memory and _____ input and output devices _______.
29, programmable controllers can use a programmer to write programs when entering instructions, based on ________ ladder diagrams and instruction tables ____________.
30, In the F20 system, the instruction mnemonic for connecting the PLC's normally open contacts to the busbar is ________LD________.
31, Inverter consists of _______ main circuit _______ and control circuit.
32, the output of the inverter is not allowed to connect _______ capacitor _______ or capacitive single-phase motor.
33, the object controlled by the CNC system is _________ servo drive ______________.
34, in the CNC machine tool, the positive direction of the machine tool linear movement of the coordinate axes X, Y, Z, specified as _____ machine ______ coordinate system.
35, the device that converts a constant voltage in a DC power supply into an adjustable DC voltage is called a __________ inverter ___________.
36. ________ Protective earthing __________ is used for electrical equipment where the neutral wire of the power supply is not directly earthed.
37, ISO is the abbreviation for _________ International Organization for Standardization ___________.
38, when operating the transistor characteristic graphic meter, special attention should be paid to the step selection of power consumption voltage and ____ polarity _____ selection switch.
39, after the inverter fault tripping, to make it return to normal state, should press ___RESET _____ key.
40, ______ electric shock ________ is the most serious electric shock accident.
41, _______ two-phase electrocution ________ is the most dangerous form of electrocution.
42, Practice has proved that low-frequency currents are more harmful _____ than high-frequency currents ____ to the human body.
43, the capacity of a single-phase rectifier transformer can be calculated by _______P2=U2I2________.
44, to carry out theoretical training, should be combined with the enterprise, ____ the occupation _______ in the production technology, quality problems in the analysis, and put forward the solution.
45. In order to improve the utilization of power supply, the inductive load circuit should be connected in parallel with appropriate reactive power compensation equipment , in order to improve the power factor.
46. A resolver is a signaling element whose output voltage varies with the rotor angle.
47 In accordance with the process requirements, in the electrical overhaul, first of all, cut off the main power supply, and do a good job of preventive safety measures.
48. Thermocouple output of the thermal potential, is gradually rising from zero, after reaching the corresponding temperature, it is no longer rising and present a plateau value.
49. Instructional training is a very important way and means to develop and improve the independent operation skills of the trainees.
50. Theoretical training is designed to enable students to master the technical and theoretical knowledge of the level of maintenance electrician through classroom teaching.
51 polyharmonic oscillator, also known as unregulated circuit.
52. Temperature measurement with a fast thermocouple is a dynamic temperature measurement.
53. In logical operations, A + AB = A .
54. CNC device is the core of the CNC system, its components include CNC hardware and software.
55. Power field effect transistor is characterized by: gate of the static internal resistance is high, the drive power is small, the withdrawal of the gate signal can be automatically shut down, while there is no second breakdown, the safety of the working area of a wide range.
56. In the instruction and independent operation training, attention should be paid to let the trainee repeated opposing practical operation training.
57. Schottky diodes and ordinary rectifier diodes, compared with the reverse recovery time is short, high operating frequency.
58. Operational amplifiers are basically composed of high input impedance differential amplifiers, high gain voltage amplifiers and low impedance output amplifiers.
59. Nowadays, digital multimeters generally use LED displays.
60. A maintenance electrician's crew is mainly for production.
61．The trainee's hands-on ability will be enhanced and improved through instruction, and the trainee will be able to master the operating skills.
Selective questions:
1. The waveform observed on an oscilloscope is accomplished by (B).
A, filament voltage B, deflection system C, accelerating pole voltage D, focusing pole voltage
2. Thermal relay of the thermal element of the rectification current IFRN = (A) IMN.
A, 0.95 ~ 1.05 B, 1 ~ 2 C, 0.8 ~ D, 1 ~
3. Traction machinery (such as trolleys, mechanical cars, battery cars), and large-scale Rolling mills, are generally used in DC motors rather than asynchronous motors, the reason is that the asynchronous motor (B).
A, low power factor B, poor speed performance C, starting torque is small D, starting current is too large
4. standard linear induction synchronizer in practice, the most widely used, the length of each piece of (D).
A, 100mm B, 1cm C, 1m D, 250mm
5. The host part of the thermometer by the A/D converter, (B) series of microcontroller minimum system and human-computer dialogue channel.
A, Z80 B, MCS-51 C, 32-bit D, 16-bit
6. Repeated grounding is to reduce the leakage of the equipment shell of the voltage to ground, to mitigate the danger of (C) disconnection.
A, ground B, phase line C, zero line D, equipment
7. Without distinguishing between the polarity of the meter pen, can measure the amount of direct current meter is (B).
A, magneto-electric system B, electromagnetic system C, electrostatic system D, electric system
8. Maintenance electrician in the operation, pay special attention to (B) problems.
A, wear safety equipment B, safety accident prevention
C, work with electricity D, safe and civilized production behavior
9. thermocouple output ( B ), is gradually rising from zero to the corresponding temperature, and then no longer rise to a plateau value.
A, resistance value B, thermopotential C, voltage value D, impedance value
10. ( D ) will regularly control the main switch in the inverter on and off, so as to obtain an arbitrary frequency of three-phase output.
A, chopper B, inverter
C, control circuit in the inverter D, inverter in the inverter
11. In overhauling or replacing the ammeter of the main circuit, a maintenance electrician will remove the ammeter by placing the current transformer in the secondary circuit (B).
A, disconnect B, short circuit C, do not have to deal with D, cut off the fuse
12. transistor graphic instrument to measure the triode, adjust the (C) can change the spacing between the characteristic curve family.
A, step selection B, power consumption resistance
C, collector-base current/potential D, peak range
13. In the filtering of transformer oil, you should first check the oil filter intact, and (B), the oil filtering site is strictly prohibited smoke and fire.
A, connected to the power supply B, connected to the ground C, insulation protection D, power-off operation
14. Electrical control circuit design should maximize the need to meet (D).
A, voltage B, current C, power D, mechanical equipment processing technology.
15. Repair work, in accordance with the equipment (A) to repair, strictly grasp the quality of repair, shall not reduce the original performance of the equipment.
A, the original data and accuracy requirements B, the degree of damage
C, operation D, repair process requirements
16. Measurement of rolling force of rolling mill, usually choose ( .B) as a sensor.
A, pressure sensor B, piezomagnetic sensor
C, Hall sensor D, piezoelectric sensor
17. The output of the frequency converter is not allowed to be connected to ( C ).
A, pure resistance B, inductance C, capacitors D, motor
18. Require a high stability of the transmission ratio of the occasion, it is appropriate to use (A) transmission.
A, gear B, belt C, chain D, worm gear
19, the most ideal working voltage of electrical equipment is its (C)
A, allowable voltage B, supply voltage
C, rated voltage D, minimum voltage
20, inverter in the fault tripped, in order to return to the normal state should be the first to press the (C) key.
A, MOD B, PRG
C, RESET D, RUN
21, ( A ) is the most dangerous form of electric shock.
A, two-phase electrocution B, electric shock
C, step voltage electrocution D, single-phase electrocution
22, strengthen collaboration is ( D ) the basic requirements of the code of professional ethics
A, law-abiding B, fairness
C, hard-working and thrifty D, unity and mutual assistance
23, through ( D ), can make trainees' hands-on skills constantly strengthen and improve, so as to master the operating skills.
A, demonstration operation B, safety education
C, on-site technical guidance D, guidance operation
24, no speed sensor regulating system speed regulation accuracy and range, is currently ( C ) vector control system with speed sensor.
A, more than B, equivalent to
C, lower than D, much lower than
25, inverter and motor between the general (B) access to the contactor.
A. allowed B. not allowed
C. need D. do not need
26, the thermometer consists of two parts, namely ( A ) part and the host 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, the measurement of inductance size, should be used (C).
A, DC single-arm bridge B, DC double-arm bridge
C, AC bridge D, multimeter
29, B2010 gantry planer V55 system, when the motor is below the rated speed, the (C) way to speed control.
A, constant power B, constant torque
C, constant torque D, weak magnetic
30, the center of the two axes is a large distance, the general choice of (B) transmission.
A, gear B, belt
C, fixed ratio D, worm gear
31, electrocuted people ( A ) when artificial respiration should be carried out.
A. heartbeat without breathing B. breathing without heartbeat
C. neither heartbeat nor breathing D. both heartbeat and breathing
32, the basic principle of socialist professional ethics is (C).
A, ****productivism B, syndicalism
C, collectivism D, wholeheartedly serve the people
Three, judgment questions
(N) 1. The input stage of an integrated operational amplifier employs a basic amplification circuit.
(Y ) 2. 555 precision timer can be applied to pulse position adjustment.
(N ) 3. The basic waveforms of electronic display devices such as TVs and oscilloscopes are rectangular and sawtooth waves.
(N) 4. A fuse must be added to the secondary circuit of a current transformer.
(N) 5. In a system with static differential speed control, the effect of disturbances on the output is fully compensated.
(N ) 6. The main circuit of the frequency converter, including the rectifier, intermediate DC link, inverter, chopper.
(Y) 7. The control object of a numerical control system is a servo drive.
(N ) 8. The resistor at the output of the integral operational amplifier should be connected in parallel with a capacitor.
(N) 9. logic circuits in the "and gate" and "or gate" is relative, the so-called "positive and gate" is "negative or gate " and a "positive or gate" is a "negative or gate."
(N) 10. The waveform observed on the oscilloscope is accomplished by the accelerating pole voltage.
(Y) 11. fuses must be added to the secondary circuit of a voltage transformer.
(N ) 12. When the motor is below the rated speed, constant speed is used to regulate the speed.
(N ) 13. open-loop automatic control system deviation, can automatically adjust.
(Y) 14．After the inverter is tripped by a fault, it should be restored to the normal state by pressing the RESET key.
(Y ) 15. according to the composition of the numerical control device, analyze the numerical control system including numerical control software and hardware two parts.
(Y) 16. three-phase half-controlled bridge rectifier circuit, the thyristor withstand voltage value for the transformer side voltage has the value of times.
(N) 17. capacitor discharge circuit must be equipped with fuses.
(Y) 18. basic integral operational amplifier, consists of a resistor connected to the inverting input, and the output to the inverting input capacitance.
(Y) 19. 555 precision timer can be applied to a pulse generator.
(Y) 20. motor "with disease" operation is an important cause of motor damage.
(N) 21. The OUT instruction is an instruction to the drive coil and is used to drive various relays.
(Y) 22. The withstand value of thyristor in three-phase half-controlled bridge rectifier circuit is times the RMS value of the secondary voltage of the transformer.
(N) 23, crystal transistor for switching use, should work in the amplification state.
(Y) 24, the core of the transformer must be grounded.
(N ) 25, inverter and motor generally need to access the contactor.
(N ) 26, the direction of Moore's stripes and grating engraved line direction is the same.
( N ) 27, A thyristor inverter is a device that converts AC electrical energy into DC electrical energy.
(N ) 28, the output of the inverter is not allowed to be connected to an inductor.
( Y ) 29, the distribution cabinet, generally put the terminals on the leftmost and lowest side.
(N) 30, a sudden blackout will produce a large number of scrap, a large number of production cuts in the economy to cause greater losses in the load of electricity, "secondary loads.
(Y) 31, to establish a correct outlook on life is a prerequisite for the cultivation of professional ethics.
(Y) 32, 35KV cable feeder section, the requirements of the cable and the overhead line connection must be equipped with a discharge gap.
(Y) 33, professional ethics is to prompt people to comply with the ideological basis of professional discipline.
Four, short-answer questions
1, what is the motor "crawl", how to debug?
Answer: the given voltage is zero, the motor speed should be zero, if not zero that is known as motor creep. 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. Change the given voltage positive or negative, motor steering change, then debugging normal.
2, CNC machine tool instruction code is mainly what?
Answer: preparation function G instruction; feed function F instruction; spindle speed S instruction; tool function T instruction; auxiliary function M instruction.
3, cage-type asynchronous motor IMN = 17.5A, do "a single infrequent start or stop, and long-term work", as well as "a single frequent start or stop, and long-term work", the melt current should be how much?
Answer: 1, a single infrequent start or stop, and long-term work IFUN = (1.5 ~ 2.5) IMN = (26.25 ~ 43.75)
2, a single frequent start or stop, and long-term work IFUN = (3 ~ 3.5) IMN = (52.5 ~ 61.25)
4, as shown in the figure is what kind of CNC system and what are the characteristics from the figure.
Answer:It is a single-axis semi-closed-loop CNC system. With high stability, is currently a system commonly used in CNC machine tools, which is characterized by the addition of encoders on the servo motor, by detecting the servo motor angle, indirectly detecting the displacement of the moving parts, and then feedback to the CNC device to participate in the adjustment.
5, inverter wiring installation considerations?
Answer:1, between the power supply and the inverter to access the low-voltage circuit breaker and contactor, to protect the inverter and facilitate the installation and maintenance; 2, between the inverter and the motor is generally not allowed to access the contactor; 3, the inverter does not generally need to connect the thermal relay; 4, the output side of the inverter is not allowed to connect the capacitor and capacitive single-phase motor.
6, calculation question: in the design of the motor electromagnetic detentor selected for instantaneous detentions set current, known as In = 12.4A, Ist/In = 5.5, the maximum and minimum value of the set current.
Answer: because I ≥ KIST where K is 1 ~ 7, so 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 detection.
Answer:1, there is no mechanical connection between the detection object and the industrial TV camera, multiple cameras can be used to get the spatial information; 2, a large amount of information can be read out in a short time; 3, useful feature signals can be extracted from the video and converted into electrical signals in a certain way to be used as arithmetic, detection and control.
8, inverter external interface circuit consists of which parts?
A: 1, multi-function input terminals and output contacts; 2, multi-function analog input/output signal contacts; 3, digital signal input/output contacts; 4, communication interface.
9. In reading the technical manual of CNC machine tools, analyze each local circuit, but also what the overall check of the map, in order to understand the overall content of the control system.
A: but also check the entire control circuit, to see if there are omissions, especially from the perspective of the whole to further check and understand the link between the various control links to achieve a full understanding of the role of each part of the schematic diagram, the working process and the main parameters of the purpose.
10. microcomputer thermometer for temperature dynamic sampling, the platform value of the specific program is what.
Answer: first of all, the average of several sampling values, followed by the deviation of each sampling value and the average value, the maximum deviation value. Judge whether the maximum deviation value is less than the given error range, if the error is exceeded, then discard the sampling value corresponding to the maximum deviation value, and take the average of the sampling value left behind as the platform value.
11. What are the basic aspects of AC motor relay contactor circuit design.
Answer: 1, to determine the type of current and the number of voltages in the control circuit; 2, motor start, forward and reverse, braking, speed change and other control of the main circuit and its protection link design; 3, control circuits, executive circuits, interlocking protection links, signaling display and safety lighting and other auxiliary circuit design.
12. CNC machine tools on the position detection device requirements.
Answer: CNC machine tools on the detection device requirements are: high reliability and anti-interference ability; to meet the requirements of machine tool machining accuracy and machining speed; easy to use and maintain; low cost.
13. gear drive has what characteristics.
A: 1, high efficiency; 2, compact structure, small size; 3, reliable, long life; 4, stable ratio; 5, manufacturing and installation of high precision requirements, expensive; 6, should not be used in the transmission distance is too large occasions.
14. In the production information automatic speculation and processing system, the upper computer to complete which work.
Answer: the collection and storage of processing quality information, the formation of management documents, the lower computer action monitoring; control quality monitoring.
V. Discussion questions
1, to three motors in the order of M1, M2, M3 start, in the order of M3, M2, M1 stop. Design the electrical schematic for control with push buttons.
2. Write the program statements for the ladder diagram of a device for sequential control as shown in the figure.
3, three motors M1, M2, M3, when M1 start time t1 after M2 start, and then after time t2 after M3 start; stop M3 first stop, after time t3 after M2 stop, and then after time t4 after M1 stop. Please design the electrical control schematic.
Answer:
4. Write the program statements for the ladder diagram of a multisegment speed control as shown in the figure.
(Diagram omitted)
5.Discuss the significance of career choice.
6, try to discuss the need to strengthen the professional ethics
7. Methods of analyzing electrical faults in hydraulic systems.
A: 1) in many cases, you can try to analyze the electrical system to analyze the hydraulic system
2) make full use of the electrical system maintenance knowledge and experience, help the hydraulic system failure repair
3) found external abnormal phenomena, comprehensive analysis of the fault of the internal rules, mastering the correct method, you can find out the fault.
8. The basic structure of the inverter and keyboard configuration.
A: The inverter consists of the main circuit and control circuit. The main circuit includes: rectifier, intermediate DC link, inverter.
The keyboard configuration has: mode changeover keys, increment/decrement keys, read-write keys, run operation keys, reset keys, and numeric keys.
9. Self-diagnostic function of the CNC system and alarm processing methods
A: 1, power on self-test: CNC system power on, the system's internal self-diagnostic software on the system of key hardware and control software one by one to carry out testing. Once the test can not pass, it will display the alarm information on the CRT, pointing out the fault parts. Only all through to enter the normal operation of the ready state. Power-on self-test can generally locate the fault to the circuit or module or even chip. But sometimes need to further inspection, judgment to find the cause of the fault and eliminated. 2, real-time self-diagnosis: CNC system in normal operation, at any time on the internal system, servo system, I / O interfaces, and other external devices of the CNC device for automatic testing and inspection, and display relevant status information. If a problem is detected, the alarm number and alarm content are immediately displayed, and according to the nature of the fault automatically decide whether to stop the action or shutdown. During the inspection, the maintenance personnel can further diagnose and troubleshoot the fault based on the alarm content, combined with the NC internal key flag registers and the PLC's operating unit status displayed at the right time.3. After troubleshooting, the alarms are often not automatically eliminated. According to different alarms, you need to press the "RESET" or "STOP" key to eliminate, or need to power reset, shutdown and restart method to eliminate, in order to restore system operation.