A look at the interview questions of a maintenance electrician can be done.
I am applying for an electrical maintenance engineer's interview question. I am going to a question and answer interview for a business interview. I will send it to everyone on the Internet to discuss it (probably the meaning is right)
1. What is the difference between a DC motor and an AC motor, and why it can be rotated.
2. Say what you need to do before using a new motor (electrical and mechanical).
3. Can you tell us about several cable specifications (listed in; 0.5mm square, 1.0mm square, 1.5mm square –)
4. When the inverter is running with the motor, use the Fluke digital multimeter to measure the frequency of the outlet terminal of the inverter. Why do you sometimes measure several thousand HZ frequencies?
5. What is the effect of the braking resistor of the frequency converter.
6. A motor needs to be started frequently, and what kind of inverter (inductive or capacitive) should be used.
7. One motor runs with gearbox, the gearbox is 10:1. When the gearbox is broken, can you remove the gearbox and change it to inverter to achieve 10:1 speed, and explain the reason.
8. Say the program execution process of plc.
9. Draw a circuit diagram of a double switch to control a lamp.
10. Tell a story about your previous electrical maintenance, and then solve it perfectly (that is, self-blowing, huh, huh)
[I don't know how my friends feel about the problem, but also to answer it, it is to interview yourself.
I haven’t come and said it for a long time, this kind of question is not very difficult, but it may be a little difficult to answer the question to the satisfaction of the person, because I am not very likely to blow.
1. The AC motor is an alternating magnetic field generated by alternating current and rotates to make asynchronous rotation. The DC motor is operated by the magnetic field generated by the main magnetic pole and the commutator. The characteristic of the DC motor is that the torque is large.
2. Before the new motor is used for insulation inspection, mechanically check whether the shell is cracked or not, and whether the bearing needs to be refueled. What motor is the new motor, power, number of revolutions, and even torque, connect 220V power supply or 380V power supply, see star type It is also a delta connection method. Generally, a new triangular motor with a choice of 4.5KW or more is required to measure the insulation between the three phases and the insulation of the opposite shells. The mechanical rotor should be flexible to rotate, the bearing has no abnormal noise, the end cap screws should be tightened, and the end cover, the base and the ground without cracking.
3. The cable used in the factory is generally less than 180 square meters, how many kinds of self check. 0.5 1.0 1.5
4. The multimeter is impossible to measure the voltage and frequency of the inverter. The Fluke digital multimeter is not used exclusively, because the frequency modulation mode of the inverter is different, and the multimeter is calculated according to a certain frequency. The multimeter can't reflect the normal reading. The multimeter can definitely measure the voltage, and the frequency of the inverter is proportional to the voltage.
5. The braking resistor of the inverter is used to consume the regenerative voltage generated by the motor without damaging the IGBT module of the inverter. The inverter only installs the braking resistor when the motor starts frequently or loses weight.
6. Use a capacitive inverter.
7. Can not be changed, because the ratio is the same, the output power is not the same, there are still many problems.
8. Three processes, scanning external input, intermediate calculation, external output, (checking the statement) PLC comes and goes without any control, communication, analog, servo, step, frequency. The non-standard equipment that has recently been used as a servo absolute position control system has finally succeeded after thousands of repeated studies.
9. The double switch I thought of myself in elementary school, and later I saw this picture in the book of junior high school.
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