污水泵软启动故障的处理（Treatment of soft start failure of sewage pump）Treatment of soft start failure of sewage pumpThe 2009-3-24Pick to: motor soft starter has been widely used in ac motor start, from all walks of life in northwest sichuan gas mine electric energy saving reconstruction project, to jiangyou zhongba gas 4 JingZhan two sewage pump start way of modification, the JingZhan two sewage pump for autotransformer start before modification, and replaced in the energy-saving renovation project for the soft starter start, but after the construction units installed panel ark electric test, found that soft starter can not work normally, based on the analysis to find the reason, will eventually troubleshooting, realized the normal start-stop of the soft starter. In this paper, the soft starter control circuit design defect is analyzed for the reference of the peer.Equipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZKey words: motor soft start faultEquipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZEquipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZ0 the introductionEquipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZThe soft starter is a motor integrated control device which integrates motor soft start, soft parking and multiple protection functions. Its main composition is concatenated between power supply and was charged with motor three instead of parallel thyristor and its electronic control circuit, through the chip control Angle of thyristor phase shift control, adjust the output voltage, the actual for thyristor ac voltage regulator. When motor starts, it as part of the input voltage, output voltage when the thyristor full conduction, output voltage and input voltage are equal, soft starter switch to bypass operation, it wont cause current mutation, the soft starter could limit the peak torque, avoid to cause water hammer; In the process of power failure, the speed of the motor can be smoothed down to zero, avoiding the sudden stop of the motor and the phenomenon of water hammer.Equipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZ1. Motor control principleEquipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZThe control principle of two sewage pump motors in the gas station in the northwest of sichuan province is shown in figure 1. QF is the main switch for low voltage power distribution cabinet, which is controlled by manual control. KMl provides power to soft starter; KM2 is the bypass operation control; KH is for motor protection; SS is the stop button; ST is the start button.Equipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZWhen QF transmission control circuit and the soft starter control electric circuit, when press the start button ST, KMl coil electricity and, KMl is a normally open contact closure, KAl to electricity, the reading of a normally open contact closure to keep the KMl, at the same time, the other pair of normally open contacts to soft starter a start signal, the soft starter.When the starting current of the motor is decreased, the soft starter automatically switches to the bypass operation, KM2 has the power to absorb and the bypass starts running, and the motor enters normal operation. When need to stop the pump, SS button, power control circuit, power KMl, soft starter and KM2 are losing electricity, KAl blackouts, control the operation of the soft starter of KAl normally open contacts disconnect, soft start, stop motor stop running.Equipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZ2 fault phenomenaEquipment management, equipment maintenance, diagnostic R4A China equipment management network http:/www.sbgl.netPHZWhen we install low-voltage distribution cabinet and good control circuit, began to try to start, press the start button, motor start normal boot, about after 5 s, the bypass relay KM2, all motor bypass pressure operation; But when the pump is stopped, when the stop button is pressed, the motor stops, the soft start the fault indicator light is lit immediately, and the second time the motor is started, it cannot be started. By checking we found that the control circuit wiring without any problem, when we first start and stop the motor, the second must press the start button, and then click the stop button, fault disappears, the fault light is put out. In the second to start and stop the motor without any reaction, when the third time press the start button, the machine can normal boot