Practice for mechanics and technicians of EMU.

Theoretical examination scope of EMU mechanic post examination

Fourth, short answer questions

1. What are the main identification marks of the EMU?

Answer: The road emblem, abbreviation of the designated road section, vehicle model, vehicle number, number of people, self-weight, load, total length, maximum driving speed, name and date of the manufacturer, and date and place of regular maintenance shall be marked with "No climbing due to high pressure danger".

2. Briefly describe the responsibilities of the on-board mechanic of the EMU.

Answer: (1) Seriously implement the rules and regulations, obey orders and commands, and earnestly perform the prescribed duties.

⑵ Be responsible for monitoring the technical status of EMU during operation, inform the driver of relevant information in time when finding faults, and take measures to properly handle them.

(3) When the EMU enters and exits the station, it is responsible for the technical handover with the EMU station.

(4) Under the command of the driver, handle the work related to driving, train protection and accident rescue.

5] When there is a fault or other emergency that endangers driving safety, timely notify the driver to take parking measures or use the emergency brake valve to stop.

[6] According to the driver's notice, be responsible for opening and closing the doors of CRH2 EMU.

3. Briefly describe how the EMU numbering rules are stipulated.

A: The model and car number of the EMU are as follows:

The technical sequence codes of the models and car numbers of various types of EMUs are allocated as follows:

BSP EMU- 1

Sifang EMU -2

Tangshan EMU No.3

Changke EMU -5

Model and serial number of each type of EMU: EMUs with different technical sequences are arranged separately, and the order is from 00 1 to 999.

Model series codes of models and car numbers of various types of emus: different model series codes are determined according to the speed grades and models of emus.

4. Briefly describe the provisions of the Ministry of Railways on the inspection quantity of wheelsets and moons of multiple units.

Answer: 1 The registered labor inspects and measures the wheelsets of the EMU every month, focusing on the technical conditions such as rims, treads, rims, brake discs and brake pads, and measuring the rim thickness, tread circumferential wear dimension, brake disc and brake pad thickness, etc.

5. Briefly describe the main responsibilities of the ground crew.

Answer: (1) Responsible for the use and management of EMU equipment.

(2) Responsible for coordinating shunting, passenger service, cleaning and pollution absorption, and checking the quality of pollution absorption.

⑶ Be responsible for the anti-freezing work of EMU.

(4) Responsible for the handover with vehicle maintenance workers.

6. Briefly describe how to specify the maintenance cycle of CRH 1, CRH2 and CRH5 EMUs.

A: The operation and maintenance cycle of EMU is divided into Grade I and Grade II. The first-class maintenance shall be carried out after each operation or within 48 hours (the cumulative operation of CRH 1, CRH2 and CRH5 shall not exceed 4,000 kilometers). Secondary maintenance is divided according to various types of EMUs, CRH 1 type once every 15 days, CRH2 type once every 30,000 kilometers or once a month, and CRH5 type once every 60,000 kilometers.

The periodic maintenance cycle of EMU is divided into three levels, four levels and five levels. According to the types of emus, the maintenance cycle of CRH 1 and CRH5 is the same, with the three-level maintenance of 6.5438+0.2 million kilometers, the four-level maintenance of 2.4 million kilometers, the five-level maintenance of 4.8 million kilometers, the three-level maintenance of CRH2 of 450,000 kilometers, the four-level maintenance of 900,000 kilometers and the five-level maintenance of 6.5438+0.8 million kilometers.

7. What measures should be taken when maintaining or working near the electronic equipment of EMU?

Answer: When maintaining or working near electronic equipment, special protection must always be used for sensitive parts, and the body should be grounded with an electrostatic wrist strap to prevent electrostatic damage to electronic equipment such as circuit boards, computers and control units.

8. How is the trial operation of EMU supervised?

Answer: The newly-built EMUs or EMUs should be put into operation after being overhauled by Level 4 and Level 5, and the trial run distance should be no less than 500km in principle; The trial running speed of 200km/h emu 160 ~ 200 km/h, and the trial running speed of 300km/h emu/h is 250 ~ 300 km/h.

4. Briefly describe the number and installation location of temperature sensors in cab air conditioning system?

A: There are three temperature sensors in the air conditioning system of the EMU cab, namely, the return air temperature sensor and the supply air temperature sensor located in the roof air conditioning unit, and the room temperature sensor located in the cab.

5. Briefly describe the number and installation location of temperature sensors in cabin air conditioning system?

A: There are 10 temperature sensors in the air conditioning system of EMU passenger room, of which 1 fresh air temperature sensor, 1 return air temperature sensor and 2 air supply temperature sensors are all located in AHU, and the other 6 room temperature sensors are distributed in the passenger room.

6. In normal mode, which working modes can the cabin air conditioning control system set the air conditioning unit to?

Answer: In normal mode, the passenger room air conditioning control system can set the air conditioning unit into the following modes according to the cooling and heating requirements: ventilation mode, pre-cooling mode, cooling mode, preheating mode and heating mode.

7. Briefly describe the working principle of keeping braking of EMU.

A: As long as the EMU is in the state of stopping lifting the bow, it will automatically implement the braking. It can be used to prevent the train from slipping when it stops, and it can make the train run on a slope of 30‰ without slipping when it stops. Brake locking can be temporarily suppressed by the button on the driver's console.

8. How to manually open the upper pedal for maintenance?

Answer: 1. Close the air supply plug door of the upper pedal;

2. Pull the upper pedal forward and upward to a fixed position;

3. Pull out the safety bolt and insert it to prevent the pedal from retracting accidentally.

9. What are the working modes of the mode selection switch in the passenger room air conditioning control cabinet?

Answer: The mode selection switch in the cabin air conditioning control cabinet has automatic position, manual position, closed position and test position.

10、

2 1. Briefly describe the working principle of traction converter.

Answer: The working principle of traction converter is to rectify the input voltage of traction transformer into DC 1650V, and then invert it into the three-phase AC driving voltage required by traction motor. At the same time, AC876V is converted from DC 1650V DC link to the three-phase transformer of the filter box, and finally AC400V is output from the three-phase transformer to the auxiliary electrical equipment of the whole vehicle. In addition, in the process of regenerative braking, it is responsible for feeding back the electric energy generated by the traction motor to the power grid.

28. Please write down the braking type of CRH 1 EMU?

Answer: Normal braking, regenerative braking, brake braking, emergency braking, parking braking and anti-icing braking.

29. What is the main function of the traction control unit PCU?

Answer: The main function of the traction control unit PCU is to control the work of the whole converter system through DCU/L, DCU/M and DCU/A, so that the main traction system can complete the AC -DC- AC conversion process of a system, and finally drive the motor for traction, so that the auxiliary power supply system can output three-phase AC 400 V.

30. What is the function of each position of the automatic speed control selector switch?

Answer: 1, and the position on the left indicates that the coupling speed state is selected;

2. The median value indicates the normal speed state controlled by the main controller is selected;

3. The position on the right indicates that the cleaning speed is selected.

32. What does the "Class A fault" indicator light mean when it goes out and when it is red?

Answer: 1, when it is closed, it means that there is no Class A fault in the train set;

2. When the red light is on, it means that there is a class A fault in the train set.

33. Please write down the meaning of the following abbreviations for equipment installation orientation?

Answer: U-shaped underframe area/underbody area; R- roof; P- guest room area; H- the interlayer between the roof and the passenger compartment; C- cab

35. Briefly describe the working conditions of the EMU HVAC system in tunnel mode?

Answer: When the HVAC system of EMU is in fire mode, the working conditions of the unit are as follows: 1, and the fresh air damper is closed; 2. The wastegate is closed; 3. The return air damper is fully opened; 4. The exhaust fan stops working.

36. Briefly describe how many batteries the EMU is equipped with? Name its main function?

A: EMU is always equipped with five batteries, whose main function is to supply power to the control system, lighting, emergency lighting, emergency ventilation unit, radio system and other equipment of EMU.

37. What are the main control safety circuits of CRH1EMU?

Answer: It is mainly divided into traction safety circuit and emergency braking safety circuit.

38. What are the main components of EMU smoke alarm?

Answer: It is mainly composed of the main engine, control panel and various types of sensors of the smoke alarm.

39. What are the main components of the bogie primary suspension device?

Answer: 1, axle box spring; 2. Axle box vertical oil shock absorber; 3. Position the rotating arm device.

40. Which traction subsystems are connected to the traction control system?

A: Including: 1, the control system of the grid-side converter; 2. Motor converter control system; 3. Auxiliary converter control system; 4. Battery charger control system

1. How to adjust the seat orientation in the passenger compartment?

A: There is a foot switch at the lower part of the seat side. When you need to rotate, press the switch with the pedal and push the rotation direction of the seat by hand. So as to adjust that travel direction of the seat.

2. What is the working temperature of the shaft temperature detection device?

Answer: When the bearing temperature reaches a certain value or above, the temperature fuse will be blown and an abnormal shaft temperature notice will be issued. The specifications of the equipment are as follows:

Working temperature: 165℃+0℃ ~- 10℃ (temperature gradient is 5℃/ min).

Set temperature of built-in temperature fuse: 144℃

3. How to set the fire extinguisher of 3.CRH 2 car?

Answer: The setting of the fire extinguisher:

(1) 1, No.8 cars: 2 cabs, 2 passing through the platform.

(2) Cars No.2, No.3, No.4, No.5 and No.6: 1 person, 2 cars for 2 people.

⑶ No.7 car: 3 corridors and 2 crew rooms.

4. What are the operation modes of air conditioning?

A: Ventilation; Refrigeration; Heating; Forced refrigeration; Forced heating

5. How to set the temperature inside the car?

Answer: Touch the up and down keys of the air conditioner setter to enter the set temperature.

Rising: every time the key is pressed, it rises by 0.5℃ (up to 40.0℃).

Drop: every time the key is pressed, it drops by 0.5℃ (maximum 10.0℃).

Touch the setting key to complete the setting.

6. Briefly describe the function of the outer windshield.

Answer: The outer windshield is used to suppress the noise from the side of the car body, prevent passengers from falling off when parking, suppress the vibration of the car body, and make the vehicle connection between the cars smooth.

7. What is the safety device of 7.CRH 2 racing car?

Answer: There are emergency ladders, transition boards, fire extinguishers, fire alarm buttons, emergency alarm buttons and emergency buttons in toilets.

8. What are the main components of the UHV electrical system of EMU?

Answer: The UHV electrical system of EMU consists of pantograph, protective grounding switch EGS, fault isolating switch, vacuum circuit breaker VCB, lightning arrester, high-voltage cable and high-voltage connector.

9. What information can the train control vehicle-mounted equipment obtain from the ground information obtained from the ground transponder through the transponder information receiving antenna and the transponder information receiving unit (BTM)?

A: Get information on the front line; Determine the position of the train; Determine the running direction of the train; Obtain route information; Obtain temporary speed limit information.

10. Can you tell me the steps to remove the brake pads?

Answer: (1) Cut the lock wire of the lower bolt; ⑵ Loosen the bolts and remove the bolts and flat washers (pay attention to prevent the brake pads from falling off); (3) Block the base of the brake pad with the spring pin and rotate it to the opposite side of the axle, and pull out the brake pad (when the brake pad is fixed and difficult to pull out, use the pull-out hole of the brake pad to pull out).

1 1. Please tell me how to repair the toilet flushing device.

Answer: (1) Remove the toilet auxiliary nozzle (3 places) and clean the nozzle part.

(2) Blow out the main nozzle of the toilet (1).

(3) When the washing water flows out abnormally, replace the main nozzle or the auxiliary nozzle with a new one.

(4) Put the urine scale remover into the toilet and clean the flow pipeline.

12. Please tell me how to repair the urine flusher.

Answer: (1) Open the inspection cover on the upper part of the urinal and replenish the treatment agent to the treatment agent cylinder. When adding the treatment agent, it is necessary to remove the mounting screw of the urinal cover and the cover under the induction state of the photoelectric sensor, and check the appearance of the pipeline system for corrosion and water leakage. (3) Cleaning the urinal deodorizing valve and the inner wall of the urinal drain pipe with a urolithiasis scavenger.

13. Please tell me how to repair the dirt box device?

Answer: (1) Check the appearance of the box, and there is no deformation or crack. ⑵ Check that the suction port and suction valve should be free from deformation, crack and damage. (3) Check that the inlet valve has a good appearance and the valve plug is flexible. (4) Open the dirt box switchboard to check the appearance, and all electrical appliances and wiring are normal.

14. What are the control functions of the service equipment of the on-board information system of CRH2 EMU?

Answer: (1) controls the display content of vehicle information display and destination display; ⑵ Control the display content of the vehicle number display; (3) transmitting broadcast time information to automatic broadcast equipment; (4) sending kilometer mileage information to broadcast service equipment; 5] Turn off the broadcast output of other groups when unpacking; [6] Control and status display of service equipment (air conditioning, indoor lights, broadcasting).

15. What are the data recording functions of CRH2 EMU on-board information system?

Answer: (1) Record the action information when the equipment fails; (2) Record the state when the main fault occurs; (3) Cumulative running kilometers and traction/regenerative power; (4) During the official operation or trial operation, information such as vehicle performance, project selection, air conditioning operation rate, air conditioning operation status, etc. shall be recorded.

16. Could you tell me the operation process of antifreeze and drainage for CRH2 EMU?

Answer: Pipeline drainage with pressure maintenance function (running when there is electricity) → Vehicle drainage (warm water tank, electric tea stove, water storage pipeline and rain scraper) → Water pump drainage → Water equipment drainage on the vehicle → Water tank drainage → Sewage tank emptying → Water seal drainage.

17. what are the main characteristics of CRH 2 emu bogies?

Answer: Lightweight design, welded frame, secondary air spring, disc brake, positioning of rotating arm axle box, single pull rod traction, motor suspension, etc.

18. The EMU displays train signs at the front and rear respectively, in the same way as at night, and it is not required to display them during the day. Explain how it is displayed?

A: The headlights in the cab at the front end of the EMU show white light forward, and the headlights in the cab at the rear end of the EMU show red light backward. When the EMU has no power loop, the cab at the first end of the running direction will display white light forward, and the cab at the rear of the running direction will display red light backward without hanging side lights.

19. Briefly describe the state of each display light when the CRH2 side sliding door is switched.

Answer: When the side sliding door is closed, the door closing indicator light on the driver's desk lights up and the car side indicator light goes out. When the side sliding door encounters an obstacle and cannot close the door or the door closing switch does not work normally, the vehicle side indicator light will light up and the driver's cab will go out.

20. Briefly describe the operation process of bicycle mitigation?

Answer: Open the main operating cabinet, turn on the corner cock of the train pipe, and then pull out the emergency button to short-circuit the vehicle brake circuit.

2 1. Briefly describe whether the air conditioning device and lighting are cut off when the EMU passes through the phase zone, and explain the reasons.

Answer; When the EMU passes through the phase zone, the air conditioner and lighting system are cut off; Because the control system of the EMU has set a delay time of 20 seconds, during this period, the lighting on the EMU will not be cut off and the air conditioning device will stop working.

22. What is auxiliary braking?

Answer: It is set for use when the brake control device is abnormal and the brake command line is disconnected. It is used in rescue. The setting switch of the operating bridge and the action of the switch board of each unit (Tc car) are different from ordinary and fast braking, and the braking force is a constant value independent of speed.

What are the functions and characteristics of 1.CRH 1 EMU tunnel mode?

Answer: It is used to prevent the bad air from the outside from entering the train compartment and affecting the air quality inside the train when the EMU passes through the tunnel. At this point, the wastegate of HVAC system is closed and the return air door is opened.

2. Briefly describe the operation of the HVAC system of CRH 1 EMU in fire mode?

Answer: When the HVAC air conditioning system of the EMU is in fire mode, the working conditions of the EMU are as follows:

1, stop the cooling or heating function of the air conditioning system;

2. The fresh air damper and waste air damper are in full open position, and the return air damper is in normal position;

3. The two exhaust fans will remove the smoke in the car with maximum airflow.

3. What are the maintenance levels of 3.CRH2 EMU and what is the maintenance cycle?

A: There are five levels of maintenance. The first and second level maintenance is operation maintenance, and the third, fourth and fifth level maintenance is regular maintenance. First-class maintenance cycle: 4000 km or 48 hours; Secondary maintenance period: 30,000 kilometers or 30 days.

4. What protection detection items are there for the fault protection function of auxiliary power supply device of 4.CRH2 EMU?

Answer: Input overcurrent, converter overvoltage, converter overcurrent, converter overload, output overvoltage, output low voltage, detection grounding and output short circuit.

When 1 and CRH 1 EMUs are running, what should I do if the main circuit breaker fails to open as instructed?

Answer: 1 If the TP owner's circuit breaker is not opened as instructed, it is necessary to raise another pantograph according to the situation to ensure that the train set has 60% power.

2 If the main circuit breaker of Tb fails to close as instructed, two adjacent circuit breakers are locked, and the train set has 40% power. At this time, the terminal of TB train P 1 K2.T.X2 1 will be picked out and packaged, and the pin code is 1 (3 1720 1A). Then, cut off the circuit breaker of Tb car on IDU (it must be cut off! ), and then lower the bow to reset. At this time, the train will have 80% power available.

2. What high-voltage equipment is installed on the Tp roof of CRH1EMU?

Answer: It is mainly equipped with pantograph, main circuit breaker, circuit breaker, voltage transformer, current transformer, lightning arrester, RC filter unit and transient inductor.

3. What equipment is available in the crew room of 3.CRH2 EMU?

Answer: Generally speaking, there are vehicle information display, automatic playback device and amplitude control device, 20W fluorescent lamp, monitor speaker, plug-in connector, vehicle information display control device, emergency brake switch and cabin attendant side sliding door switch, as well as fire extinguishers, emergency lights and emergency brake switches.

4. Excuse me, what are the disassembly and reset functions of the on-board information system equipment of CRH2 EMU?

Answer: (1) Send reset instructions to traction converter, auxiliary power supply device and switchboard; (2) Transmission of remote dismantling instructions; ⑶ Control of auxiliary winding power supply induction circuit; (4) Three-phase AC400V power supply induction circuit control (BKK remote control switching operation).

Verb (abbreviation for verb) questions and answers

1. What are the basic requirements and operating procedures for the disconnection and power supply of the OCS of the EMU?

Answer: 1. EMU will designate a special person to be responsible for the operation and monitoring of catenary power supply and fault (one person will operate and one person will monitor), the handling and confirmation of catenary power supply and fault, and the protection and confirmation of catenary power failure and grounding. Operators of catenary power supply and power failure shall be trained and certified.

2. In principle, apply for power outage of catenary according to the time and procedure of shift operation plan, and the change of plan needs to be approved by the dispatcher.

Power failure:

(1) Before the operation of catenary power outage, the relevant maintenance personnel must apply to the dispatcher and go through the formalities of catenary power outage.

(2) The power outage operation can only be approved after the scheduling confirms that the power outage conditions are met.

(3) In case of power failure, the power failure operator should wear protection, and under the supervision of the supervisor, disconnect the isolating switch. After disconnection, test the catenary with a measuring rod. After confirming that there is no electricity, hang the grounding electrode and implement the grounding protection of catenary power failure.

(4) Before and after the power failure, the relevant ZuoYeDui shall be notified.

Power supply:

(1) Before the catenary power supply operation, the relevant maintenance personnel must apply to the dispatcher and go through the power supply formalities for the catenary.

(2) The power supply operation can only be approved after the dispatching confirms that the power supply conditions are met.

(3) During the power supply operation, the power supply workers should wear protection, remove the catenary grounding protection and close the disconnector under the supervision of the guardian.

(4) Before and after power-on, relevant ZuoYeDui shall be notified.

5. Handling the power transmission and power failure procedures of catenary must be registered and signed.

6. There should be obvious warning signs for the presence or absence of electricity on the catenary.

7. Check the power supply and disconnection tools of catenary as required.

2. Explain what the infrared axle temperature detection system provides for detecting the axle temperature of EMU and predicting the hot axle.

Answer: (1) The infrared system must detect the axle temperature of the EMU.

⑵ EMU axle temperature monitoring is mainly based on vehicle-mounted detection system, supplemented by ground infrared system detection.

(3) When the infrared system detects the EMU hot axle alarm, the infrared attendant will give an alarm to the train according to the specified procedures, but the train will not stop. The train dispatcher immediately informs the driver, and the driver immediately notifies the on-board mechanic, who determines whether the EMU will continue to operate safely according to the detection of the on-board axle temperature detection system, and the driver feeds back the handling situation to the train dispatcher, and the train dispatcher feeds back to the infrared attendant.

⑷ The thermal axle prediction standard of infrared system EMU shall be implemented with reference to the thermal axle prediction standard of passenger cars in each bureau.

3. Explain the safety regulations of CRH 1, CRH2 and CRH5 EMUs in case of water accumulation on the line.

Answer: (1) When the accumulated water level of the line is higher than the rail surface 100 mm, the CRH 1 EMU is forbidden to lift the bow for power supply. CRH 1 EMU parked on the line with water level higher than rail surface 150mm must be strictly inspected and identified before use, and submitted to the Ministry for approval.

⑵ When the line water level is 60 mm higher than the rail surface, it is forbidden to lift the bow for power supply for CRH2 EMU. CRH2 _ 2 _ 2 EMU is parked on the line 90mm above the rail surface, and must be strictly inspected and appraised before use, and submitted to the Ministry for approval.

(3) When the accumulated water level of the line is higher than the rail surface 100 mm, the CRH5 EMU is forbidden to lift the bow for power supply. The CRH5 EMU, which has been parked on the 200-mm track above the accumulated water surface, must be strictly inspected and identified before use, and submitted to the Ministry for approval.

(4) In operation, when the driver finds that the water level of the line is higher than the rail surface, he should immediately take parking measures, report to the train dispatcher, and direct the train staff to do a good job in inspection, protection and other related work.

5. Describe the fire prevention responsibilities of the on-board mechanic of CRH series EMU.

Answer: (1) Before leaving the warehouse, check and confirm the status of electrical and fire-fighting equipment according to operating standards, and conduct joint inspection and handover.

(2) Patrol and inspect the running vehicle electrical equipment, automatic fire alarm controller and other equipment as required, and handle the hidden dangers in time when found.

(3) In case of fire, according to the emergency plan of fire accident, timely notify the driver to take parking measures or use the emergency brake valve to stop; Under the command of the driver, do a good job in driving, train protection and accident rescue, and be responsible for the door operation of the centralized control switch of CRH2 EMU.

(4) Operate EMU equipment according to regulations, guide passengers to use the equipment correctly, and stop and correct violations.

5] Do a good job of safety inspection and handover after the arrival of the EMU.

1. Write the operation of the key interlock system when the inverter is unpacked. What is the main function of grounding operation?

Answer: 1. Turn the interlock switches of Tp 1, Tp2 and Tb cars to the OFF position, and take out the blue key. This operation is mainly used to cut off the gas source of the pantograph, so that the train set cannot raise the pantograph and receive the current.

2. Use three blue keys to operate the grounding interlocking mechanism on the main circuit breakers of Tp 1, Tp2 and Tb, and take out three yellow keys. The main function of this operation is to make the main circuit breaker reliably grounded.

3. Ground a yellow key on Tb bus of AC400V, and then take out a black key. The function of this operation is to ensure that the AC400V bus of the auxiliary power supply system of EMU is grounded.

4. Insert the two yellow keys and a black key removed before into the safety interlock key box on the Tb car, and take out a white key.

5. Place the grounding handle in the conversion box in the grounding position with the white key, and finally take out the red key to open the conversion box for inspection. The main function of this operation is to ground the DC link in the converter to ensure that the capacitor on the DC link is completely discharged.

6. Finally, use the removed red key to directly open the conversion box for inspection and maintenance.

2. What are the main conditions leading to emergency braking?

Answer: 1. Press the emergency stop button.

2. Put the main control handle in the emergency position.

3. Emergency braking caused by 3.DSD device

4.ATP requires emergency braking

5. During normal operation, the total wind pressure is lower than 600KPa.

6, emergency safety circuit loss of electricity

7. Brake computer requests emergency braking.

8, passenger emergency braking action

3. Write down the working principle of pantograph lifting?

Answer: After the pantograph key is pressed, the pantograph gas supply solenoid valve is energized to supply gas to the pantograph circuit. After the water is filtered by the air filter and restricted by the pantograph throttle valve, the pantograph gas path enters the fine pressure regulating valve to adjust the total wind pressure to the normal pantograph pressure of 3.2-3.8bar, and the adjusted compressed air inflates the pantograph airbag to drive the mechanical device to complete the pantograph lifting action. The action value of the safety valve is 4bar, which ensures that when the precision pressure regulating valve is damaged, the total wind pressure will not directly enter the bow airbag, resulting in airbag damage.

28. Briefly describe the startup process of traction converter LCM.

Answer: 1. The drive control unit DCU/L of the grid-side converter gets the start instruction, the charging contactor is closed, and the DC link capacitor is precharged through the charging resistor;

2. When the DC link capacitor is charged, close the line contactor.

3. The contactor of the other line is also closed, and then the charging contactor is disconnected, the charging loop stops, and the grid-side converter LCM finishes outputting DC1650 V..

29. Briefly describe the working principle of automatic switch monitoring program of CRH 1 cab rearview system.

Answer: When the cab is activated, the monitor will automatically start the automatic on/off program related to the running speed of the train set. The principle of automatic on/off program is as follows:

1. When the train set accelerates to the set value of 70km/h, the speed is transmitted from the TCMS system to the rear view system through the digital input module, and the monitor will be automatically turned off at this time;

2. When the running speed of the train set drops to 10km/h, the monitor will automatically turn on;

3. When the monitor is automatically turned off, the monitor can also manually press the standby button to stop the automatic switching program and directly start or close the display function of the monitor manually.