1、 Introduction

Metro screen door is a high-tech product integrating construction, machinery, materials, electronics, information and other disciplines. It is mainly composed of door structure, power supply system, drive system, control system, network system and so on. It is installed on the subway platform to separate the platform from the train operation area, reduce the loss of cold and hot air on the platform caused by air convection, and reduce the operation energy consumption of the station air conditioning and ventilation system. At the same time, it also reduces the impact of noise generated by train operation on the station, provides passengers with a comfortable waiting environment, improves the service quality of the station, and has the functions of energy saving, safety, beauty and so on. This paper discusses the common faults and treatment measures of Metro PSD.

2、 Analysis and treatment of common faults of Metro screen door

（1） PSD platform unit controller (pedc) failure

1. The sliding door on the whole side cannot be opened or closed

Fault analysis: signal ATC cannot open and close the sliding door on the whole side. Due to the omission in the control logic circuit design of pedc, the sliding door on the whole side cannot be closed. Pedc is composed of power board, logic control circuit board, safety relay, aviation plug, etc. it has been confirmed that there are no quality or installation problems in power board, safety relay, aviation plug, etc.

Treatment measures: restart pedc or replace pedc. The faulty pedc is returned to the factory for maintenance, but the repaired pedc still has frequent faults.

2. ISCS displays "pedc fault", but it does not affect the opening and closing of doors

Fault analysis: when this fault occurs, the local control box (LCB) and local control panel (PSL) can open and close the PSD, ISCS reports "pedc fault", at the same time, the pedc fault display of ISCS changes from green to red, and the fault history record of remote monitoring equipment (PSA) is also displayed.

Handling measures: in case of this fault, the pedc can be restarted by cutting off the control power supply. Due to the instability of Westinghouse pedc equipment, it can be handled temporarily by knocking and vibration. If the above methods cannot be recovered, the pedc shall be replaced.

3. ISCS displays "pedc channel fault", but it does not affect the opening and closing of doors

Fault analysis: the channel fault indicator flashes and ISCS reports channel fault. The reason is the single chip microcomputer fault of pedc.

Treatment measures: power off and restart the pedc. If it is still unable to recover, it is proved that the internal MCU is damaged, and the pedc shall be replaced in time.

4. ISCS displays "CANbus fault", but it does not affect the opening and closing of doors

Fault analysis: the data bus plug is loose, which affects the communication between DCU and pedc.

Handling measures: check the data bus plugs one by one, mainly check the pl7 plug, plug it firmly and tighten it.

（2） Failure and treatment of safety circuit

1. Analysis and treatment of safety circuit failure caused by travel switch the travel switch of sliding door and emergency door enters the safety circuit. Each time the sliding door is opened and closed, the travel switch must act. During the operation time from 5:00 to 24:00 every day, the train passes about 280 times. Therefore, the four travel switches in the locking mechanism must act 280 times a day. During operation, the contact of the travel switch is on and off due to vibration, but the PSD DCU does not have the function of monitoring the contact of the travel switch entering the safety circuit. When the safety circuit disconnection fault occurs, you can use the LCB switch to close each sliding door manually and observe the "close and lock" indicator light of PSL. If the indicator light of a sliding door is on, it indicates that the travel switch of the sliding door is faulty. However, due to the random occurrence of this fault, the vibration of the door body leads to the vibration of the travel switch, which sometimes makes the contact return to normal. In addition, during the peak operation, the driving interval is short, and the time is not enough to check the 24 sliding doors on the whole side. It often happens that several sliding doors are not checked. The vibration during the opening and closing action of the sliding door makes the travel switch contact return to normal again when the next train enters the station. For the above faults, it is necessary to regularly detect the travel switch. The multimeter can be used to set the resistance gear, the probe is connected to the normally open contact of the travel switch, and the thumb is used to move the roller. After the roller acts, the resistance should be 0 or less than 0.1 Ω. Move the roller repeatedly. If the resistance is infinite after the roller acts, replace the travel switch. After the opening and closing signals of the sliding door are sent repeatedly, i.e. the opening and closing signals of the sliding door are not recovered after the simulation of the opening and closing signals of the sliding door at night.

2. Analysis and treatment of safety circuit fault caused by DCU main board and connector DCU main board is installed in each sliding door machine. The power supply of the safety circuit is DC 60V, which is sent to the main board of the sliding door machine farthest from the PSD equipment room. After the normally open contacts of 120 travel switches are connected in series, this voltage is sent to the safety relay coil of the driven relay unit of PSC in the PSD equipment room, and the driven relay unit sends the "close and lock" command to the ATC equipment. During use, it is found that the pl14 and pl15 connectors on the main board are sometimes loose or individual pins are loose, resulting in the disconnection of the safety circuit. When the fault occurs, ISCS and PSA have no record of the fault door. Loose fixing screws of the travel switch and improper adjustment of the travel switch can cause all sliding doors and emergency doors to be closed and locked, and the safety circuit will be at low level. The pins shall be fastened, all plugs shall be reinstalled if necessary, and the travel switch shall be adjusted to ensure the normal operation of the safety circuit.

（3） Insulation fault of PSD

1. Insulation fault analysis of PSD

The top and bottom of the PSD structure are insulated. At the same time, the insulating belt is laid at the edge of the platform under the platform decoration layer to realize the insulation between the door and the earth and avoid the harm of step voltage to human body. As the decoration ceiling lamp belt contacts the upper cover plate of the PSD, the insulation of the door body is damaged.

2. Treatment measures

In order to avoid the insulation problem of PSD affecting the safety of riding, it can be used to stick insulating film on the metal part of PSD body. In order to ensure the safety of passengers and prevent electric shock caused by contacting the live shell (column and door frame) of PSD when boarding and alighting passengers and waiting for a train.

（4） Drive power failure

1. Uplink and downlink signals ATC cannot be switched on

Fault analysis: due to the failure of driving power supply, the PDP has no 380V AC output, the 380V / 39.4v transformer of the power supply unit of the single door has no current output, and the DCU has not been put into operation. Therefore, the LCB mode switch of the single door cannot open the sliding door, and only the triangular key can be used for the five operations of priority. The other LCB, integrated backup control panel (IBP), PSL and signal door opening are invalid. Because the DCU cannot work, so, The door status indicator is off. After this fault occurs, use a multimeter to check whether + 3-q1 and + 5-q1 in the PDP cabinet are powered, check the feed in and feed out voltage of the driving ups and bypass cabinet, check the working position and voltage of ATS, and check the working condition and fault indication of the PK module driving ups.

Treatment measures: the ATS shall be restored immediately. If the ATS is damaged, the bypass air switch shall be closed manually to restore the power supply. The electromechanical personnel shall watch on site and replace the ATS after shutdown.

2. The single rectifier and inverter power modules of the driving power ups fail and quit working. A total of 9 power modules are installed in the PK rack. A power module failure often occurs, exits work and gives an alarm.

Fault analysis: the manufacturer's equipment has certain defects. Its inverter process is operated in parallel through several inverters. Unlike DC power supply, AC power supply can be directly connected in parallel. Inverters must be connected in parallel with the same frequency and phase. If they fail to meet the specification requirements, the initial phase angle of output is different, resulting in internal current circulation and even circulation in serious cases.