电机软启动器原理图（）

电机软启动器原理图（） 电机软启动器原理图() Motor soft starter schematic 6kV motor soft starter control schematic Application of soft starter in cold shear control system 1 Preface Cold shear is essential for bar production line equipment in continuous shear line, due to cold shear positioning control of the real-time and accuracy requirements are very high, which is controlled by inverter or DC speed regulating device normally used for sizing machine; bar group length bit line, because until the bar group full stop on the table. After the cut, cut the real-time and accurate positioning control is not very high on the cold, then may consider the use of AC motor soft starter control, greatly reduce the equipment investment. Overview of 2 soft starter Soft starter is the product of the combination of power electronic technology and automatic control technology. The circuit principle is shown in figure 1. The three sets of anti parallel thyristor are connected between the power supply and the controlled motor in series. When starting, by electronic circuit to control the turn-on angle of thyristor, the terminal voltage of the motor increases gradually, until the full voltage of the motor to achieve without the impact of soft start; shutdown, the control of the thyristor turn off speed, so that the motor terminal voltage by the voltage gradually decreased to zero, soft parking so, the soft starter is actually a thyristor AC voltage regulator. By changing the trigger angle of the thyristor, the output voltage of the thyristor voltage regulating circuit can be adjusted. During the whole starting process, the output of the soft starter is a smooth step-up process (and can have current limiting function) until the thyristor is fully conducted and the motor operates at rated voltage. Figure 1 is the principle of ABB PSD series soft starter products, elements in the figures are as follows: E1: F6: circuit board; temperature monitor; J1 - J3: connecting terminal; K4: relay action in the running state; K5: relay at full pressure state (Ue=100%); K6: relay and the fault signal; current transformer; T2: T5: V1: V6 - transformer control; thyristor; X1 - X3: terminal board. In addition, according to the power range, there are two or three groups of fans as standard configurations. According to different application requirements, overload protectors can also be selected. In Figure 1, V2, V4, V6 three thyristors are corresponding to U, V, W three-phase power supply is half of the week, opening angle of the same, so the three-phase trigger pulse should be followed by a difference of 120o; positive and negative half cycle of each phase respectively by two anti parallel thyristor trigger control, so the same phase of the two anti parallel thyristor trigger pulse is 180o, V2, V5, trigger sequence is V4, V1, V6, V3, 60o sequence difference. Fig. 1 Schematic diagram of soft starter 3 control principle and software implementation Power on and starting control of 3.1 soft starter The soft starter control loop is shown in figure 2. The operator first switch on the Q50 manual, if there is no overload fault and fuse F40 normal, K51 will pull a "power ready" signal to the PLC, the operator in the HMI picture given power on command, K51 will pull to pull K10, issued a "signal of electricity" to complete the PLC. Electric operation. When starting, the operator presses the starting button from the operating platform, the motor starts at low speed to the setting value at the set starting time, and sends a "running" signal to the PLC. The brake fan also starts at the same time with the main motor. In order to protect the motor and mechanical equipment, in addition to receive signal of electricity ", also must meet the following conditions: no stop lubricating oil pump chain; operation; lubrication pressure reaches the specified value; dry oil pump; the air pressure reaches the specified value. Fig. 2 Schematic diagram of control loop 3.2 soft starter parameter settings After the soft starter is powered on, the related parameters should be set up. For the PSD type soft starter, the main parameters and settings are as follows: (1) starting time: 0.5 ~ 60s. (2) starting voltage: 10 to 60% supply voltage. (3) current limiting function: 2~5 times motor rated current. (4) time of decompression: 0 ~ 30s. After the soft starter receives the stop signal, the output terminal is lowered from the initial voltage (100% to 30% of the supply voltage) to the initial voltage according to the set down time, and then drops to zero voltage immediately. Shear control of 3.3 cold shear Shear control is essentially a brake and clutch control. The brake and clutch are respectively composed of a one-way pneumatic solenoid valve control, the control principle shown in figure 3. PLC gives the instruction given shear brake open command, 0.5 seconds after the clutch is inserted in the cut; when the detected blade close proximity switch, delay 0.61 seconds (cutting edge from the closed position to the original location of the time), cutting command canceled, clutch out after 0.2 seconds brake lock. In Figure 3, the clutch insert instructions presented again given the brake open instruction, to ensure that the brake is open during shear. The instruction given: when the shear steel head to scale machine baffle, roller stop, if the following conditions are satisfied, is given a shear command: soft starter operation; brake fan operation; no stop chain; lubrication pressure reaches the specified value; dry oil pump; the air pressure reaches the specified value; the upper and lower cutting edge locking cutting head; baffle in the upper tail; cleaning equipment in the backward position. When the head is cut, the steel head stops at the end of the cutting head and begins to shear. All shearing can also be done manually from the operating table. The interlocking conditions are the same as above. Figure 3 brake and clutch control principle diagram 4 application effect The soft starter has a solid metal casing design, suitable for various applications, including conventional startup and load start; setting potentiometer type parameters can be flexible combination on the front panel, and is equipped with LED status and fault indication clear; release protection electronic overload to provide more effective protection than conventional double metal sheet for electric machine. For cold shear, without inversion and bypass control, and power on, start, brake and clutch control are performed by PLC, the control loop is very simple. Production operation shows that soft starter control cold shear is a very economical and practical method, and the system runs stably and reliably. Abstract: This paper describes the principle, function and characteristics of large and medium-sized motor model starting controller of soft starter, and the application situation in Danjiangkou hydropower station, and for the soft start export problems and puts forward improvement suggestions and opinions, It will play an active role in improving the control function and popularization of soft starter in this field. Large and medium motor; soft starter; application; improvement The traditional large and medium-sized motor control device adopts the magnetic starter contactor, direct start stop mode, the drawback is that the control mode is simple, flexible, large impact on the system and control elements are easy to damage, maintenance workload. With the development of computer control technology has matured in recent years, with the computer as the core, using intelligent bidirectional thyristor control circuit of controller "soft starter" has been widely used in the field, with its flexible control mode is simple, little impact on the system and the control element is not easy to damage and convenient maintenance and many other advantages are gradually to replace the conventional control device. Of course, the application of new products will be exposed some problems, the soft starter in the Danjiangkou power plant used as the basis, to discuss the situation in 3 years and problems, puts forward some suggestions for improvement to make it more perfect control function from the angle of production, for manufacturers and reference. Function and characteristics of 1 soft starter 1.1 application Danjiangkou power plant 20 m 3 air compressor unit system is phase modulation, maintenance and other gas equipment source, composed of 2 air compressors and 4 gas tank, the working pressure is 0.6 ~ 0.8MPa, the motor capacity of air compressor was 132 kW, the rated current of 272 A. 2 sets of independent control system, each control 1 air compressors, has been running for more than 20 years, equipment aging serious, high failure rate. Limited by the level of science and technology at that time, the logic control loop is composed of relays, the starting mode is the traditional frequency sensitive resistor step-down mode, and the actuating component of the starting motor is a contactor. The connection of the control system is complex, the fault point is too much, the motor protection function is not complete, the starting current is large, and the utility model has a great impact on the power consumption of the factory, which is not conducive to the stable operation of other equipment. Soft starter was applied to the system at the beginning of 1997. The new control system to solve the problems of the original control system, and is conducive to the new monitoring system with computer interface is in the process of comprehensive reform, to improve the automation of the realization of its high efficiency and lay the foundation. 1.2 soft starter The soft starter is mainly composed of 8096 main board, drive board, motor main control loop and control panel of CPU. Soft starter has control function, motor protection function, and display, alarm, parameter settings function. 1.2.1 control function mode After receiving the external start and stop commands, the motor is controlled according to the preset start and stop mode. The optional start and stop control modes are as follows: (1) limiting soft start control mode: as shown in Figure 1, when the motor is started, the output voltage increases rapidly from zero until the output current reaches the set current limit of Im, and then ensure the output current is not greater than the value in the case of voltage gradually increased, the motor gradually accelerated, complete the startup process. (2) voltage ramp start control mode: as shown in Figure 2, U 1 is the initial voltage corresponding to the minimum torque required for motor start. When the motor starts, the output voltage of the soft starter rises rapidly to the setting value U 1, and then gradually increases at the set rate until the grid voltage is reached. The contactor is pulled in and the starting process is completed. (3) parking mode: the motor will decelerate gradually at the set speed until it stops completely. (4) free parking: the motor is controlled free of inertia without stopping. (5) inching function: under the control of this mode, the output voltage of the soft starter is rapidly increased to the initial voltage U 1, and the output voltage value is maintained. 1.2.2 motor protection function The motor protection functions of the soft starter include phase sequence protection, phase fault protection, start over-current protection, overcurrent protection, overload operation protection and motor protection for long time. When the protective function of the soft starter is operated, the soft starter will generate a stop output and display the reason directly on the control panel. 1.2.3 display, alarm and parameter setting function On the control panel of the soft starter, the motor current, the alarm signal and the set parameter value can be displayed. The motor protection value and the motor operation mode are set up in digital form, and the motor is started and stopped manually. The working principle of soft starter is: soft starter after receiving a start command, then press the start mode set by the corresponding calculation, determine the output voltage of the controllable silicon trigger signal, to start the process control of motor. When the starting process of the motor is completed, the soft starter controls the AC contactor to pull in, and the short circuit is connected with all the controllable silicon, so that the motor is directly operated in the network to avoid unnecessary energy consumption. Fig. 3 is a schematic diagram of a soft starter. 1.3 、 soft starter used in Danjiangkou power plant 1.3.1 system structure The structure of the control system is shown in Figure 4. It mainly includes soft starter, programmable controller, pressure sensor and intake solenoid valve. Main functions of 1.3.2 system (1) control function; Automatic / manual control of air compressor starting and stopping. The mode of control is switched by working mode switch selection. Automatic operation mode, according to the change of air tank pressure, automatic start and stop air compressor. Manual mode, the programmable controller out of operation, in the soft starter control panel manually operated start and stop air compressor. According to the actual situation of 20m 3 air compressor system, the starting and stopping modes of motor are limited current soft start and soft stop. (2) protection function; The protection function concerns the whole air compressor system. When the first stage cylinder pressure is too high / low, the cylinder pressure is too high / low, the exhaust temperature is too high, as well as any phase abnormality such as phase interruption, phase sequence error, motor flow, overload, etc., the protection action stops automatically. (3) monitoring and alarming function; Operation of real-time monitoring system, the control panel is provided with a main circuit current and voltage and display the running state of the system indicates that when the system fails, the control panel with fault alarm display, and send the alarm signal to the control room. 1.3.3 system working principle When the pressure of the air tank is lowered to the starting value of the air compressor, the programmable controller sends a start command to the soft starter, The soft starter controls the starting voltage and current of the motor through the silicon controlled rectifier, so that the air compressor system is smoothly started to no-load. When the voltage reaches the rated value, the contactor draws in, the thyristor is short circuited, the three-phase power supply is directly added to the motor, the soft starter is started and completed, and the programmable controller is started to complete the signal. The programmable controller after 9 s delay, for the air inlet electromagnetic valve, air compressor with load operation to tank pump; when tank pressure up to stop when the value of PLC cut air solenoid valve, the air compressor system enters the idle state, after 2 s to send the stop order in soft starter, soft starter under control motor, gradually slow down to a complete stop. 2 operation effect and improvement suggestion The operation of the new control system for 3 years shows that the reliability, function and performance of the new control system have been significantly improved and improved compared with the original control system. Mainly reflected in the following points: (1) in the structure of the soft starter output as the control actuator, with programmable controller to realize logic control, which makes the system simple and clear structure, improve the reliability of the control system, the maintenance is convenient. (2) the current limit starting mode of the soft starter controls the starting current in the safe range, and improves the condition that the original control system influences the normal operation of other equipment because the starting current is larger and the power consumption of the impact factory is affected. (3) to start the process of using triac, the startup process is completed, the control mode of short circuit thyristor contactor, which avoids the direct control of motor contact arc, easy adhesion, burned fault contactor, but also save energy. (4) soft start and soft parking, reduce mechanical stress, protect equipment and prolong service life. (5) the protection function involves the bad operation conditions of the air compressor system, which is beneficial to improve the health level of the equipment. (6) the display function on the control panel, so as to fully understand the operation of the equipment at the scene. (7) the functions of setting and displaying digital parameters are visual, convenient and time-saving. The soft starter, anti-interference ability is an important index of the reliability in operation, soft starter for 3 years, had the device with a false start power transient phenomenon, therefore, aiming at the existing problems of soft starter, we put forward the following suggestions and improvement measures for manufacturers reference: (1) to prevent device power immediately after the false start phenomenon, suggest manufacturers of the control software to modify, add a delay function block in the final exit signal loop device software, how much delay time to avoid interference signal is the premise of the need to debug, or add a time delay relay in the final signal hardware outlet circuit, can effectively solve the problem of interference. (2) for the convenience of maintenance, the soft starter can hope in the load in normal operation for exit and investment, that is to say in the process of the normal operation, if you turn off the soft starter corresponding control device of power system operation mode, keep the original state unchanged, this can be soft starter device on fault repair, maintenance after directly soft starter control device for power supply is closed, and the operation mode (i.e. automatically follow the device software requirements), This function is very suitable for site routine maintenance. (3) it is suggested that the soft starter device be modular and easy to maintain. 4 Conclusion Air compressor, pump, fan and other auxiliary equipment in the hydropower station and many industrial control areas, using the traditional control structure has many defects, for the heavy load, the problem becomes more prominent, the soft starter not only overcomes the shortcomings of traditional control structure, but also make the control functions more perfect. With the continuous progress of technology and the continuous improvement of soft starter, soft starter will be more mature. Therefore, it is an inevitable trend for soft starter to be widely used in large and medium-sized motors.