Zhang Xiumei (1. Assistant Engineer, Power Plant of Qihua Group, Qiqihar, Heilongjiang 161033)
Our company installed a domestic LW520xl247-N 90kw horizontal screw discharge sedimentation centrifuge. The centrifuge has a large starting current, a large starting torque and a long starting time. According to the information provided by the factory, when the centrifuge is started directly, the starting current reaches 2 000A, and the starting time is close to 40s. Starting in this way, a larger transformer capacity will be required, and a large line voltage drop will cause other The device is not working or even shuts down. If a conventional auto-coupled step-down start is used, the starting current is reduced and the starting torque is reduced by about 60%, thereby extending the starting time, which greatly exceeds 40 S, which is not allowed in the production process. After the technicians consulted the data, the research decided to use the American company AB SMC PLUS intelligent motor controller, that is, the soft starter.
1 US SMCPLUS intelligent motor controller introduction US SMC PLUS intelligent motor controller is the United States Allen-Bradley company products, also known as soft starter, the company has STC, SMC-2, SMC PLUS and SMC Dialog plus 4 series, rated voltage 200 ~ 60O V, rated current 24 ~ 1 000 A. These controllers have ramp start, current limit start, full pressure start, dual ramp start, pump control, preset low speed operation, intelligent motor braking, low speed operation with brake, soft stop, accurate stop, energy saving operation and fault diagnosis And other functions.
The soft starter consists of the main working circuit and the control system. The main working circuit is mainly composed of three opposite parallel thyristor voltage regulating and speed regulating circuits connected in series between the power supply and the controlled motor. Use the electronic switching characteristics of the thyristor. The degree of conduction of the thyristor is changed by controlling the trigger pulse and the firing angle by the single-chip microcomputer in the starter. Thereby completing the starting process.
2 Starting effect and advantages After the setting and debugging, the centrifuge starts smoothly, the starting time is less than 40 8, the production process meets the requirements of the production process, the starting current does not exceed 800 A, the impact on the power supply system is small, and the starting effect is good.
Soft starters have the following advantages over conventional auto-coupled buck starters:
(1) The soft starter fundamentally solves the impact of the instantaneous current spike generated by the auto-coupled buck starter by switching the voltage of the contactor to achieve the purpose of step-down. It is a non-contact control device, and there is no contactor belt. The load is switched, causing the contact arc to burn out.
(2) Limit line voltage drop and reduce current peak during start-up.
(3) Depending on the load, a variety of starting and stopping modes can be selected. A single soft starter can start multiple motors at different times, and the motor can achieve energy-saving operation when lightly loaded. In addition, the soft starter also provides functions such as overload protection, phase loss, rotor stall and other monitoring protection and rapid diagnosis of fault information.
3 Soft starter operation mode improvement and use should pay attention to Use the above wiring method to start and drag the centrifuge, the soft starter is always in working state. This is not conducive to fault repair and shortens the life of the soft starter. In order to facilitate maintenance and extend the service life. It is conceivable to add an isolation contactor at the lower end of the soft starter, and connect the contactor (K) or the bypass contactor at both ends of the two isolation contactors as shown in Fig. 2. When the soft starter is started.
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The bypass contactor (K) is turned on, the isolating contactor at both ends of the soft starter is disconnected, and the soft starter is cut off, thereby achieving the purpose of convenient maintenance and prolonging the service life. If the motor needs to be stopped, the bypass contactor (K) can be directly disconnected, but this operation is easy to burn out the bypass contactor contact, and it is possible to consider switching to the soft starter and stopping by the soft starter. The soft starter only operates during start and stop, which in turn reduces harmonic pollution to the grid due to long-term operation of the soft starter.
When using the soft starter, it should be noted that in addition to its rated parameters, the main reason is that the environment is very clean and dry, which can eliminate the electrical fault caused by dust and moisture. In practical applications, the SCR fuse is blown due to large environmental dust and tidal temperature, and the soft starter cannot work. Followed by the ambient temperature and humidity, the operating temperature must be maintained between 0 ° C and 50 ° C, the device does not condense in the soft starter. In addition, when installing the soft starter, there should be enough space above and below it to facilitate heat dissipation. At the same time, it should be noted that when the overheating relay is also installed in the same chassis, a partition should be placed around the relay. In order to prevent the strong cold air flow from directly blowing onto the relay, the effective protection function is lost.
4 Conclusion The soft starter successfully activated the centrifuge, which is the starting of high-power motors and the dragging of heavy-duty equipment. Found a better way. It is worth promoting and learning. When the soft starter is selected and used, it must be strictly in accordance with the production process requirements and installation conditions, so that the soft starter can be used economically and prolonged.
Our company installed a domestic LW520xl247-N 90kw horizontal screw discharge sedimentation centrifuge. The centrifuge has a large starting current, a large starting torque and a long starting time. According to the information provided by the factory, when the centrifuge is started directly, the starting current reaches 2 000A, and the starting time is close to 40s. Starting in this way, a larger transformer capacity will be required, and a large line voltage drop will cause other The device is not working or even shuts down. If a conventional auto-coupled step-down start is used, the starting current is reduced and the starting torque is reduced by about 60%, thereby extending the starting time, which greatly exceeds 40 S, which is not allowed in the production process. After the technicians consulted the data, the research decided to use the American company AB SMC PLUS intelligent motor controller, that is, the soft starter.
1 US SMCPLUS intelligent motor controller introduction US SMC PLUS intelligent motor controller is the United States Allen-Bradley company products, also known as soft starter, the company has STC, SMC-2, SMC PLUS and SMC Dialog plus 4 series, rated voltage 200 ~ 60O V, rated current 24 ~ 1 000 A. These controllers have ramp start, current limit start, full pressure start, dual ramp start, pump control, preset low speed operation, intelligent motor braking, low speed operation with brake, soft stop, accurate stop, energy saving operation and fault diagnosis And other functions.
The soft starter consists of the main working circuit and the control system. The main working circuit is mainly composed of three opposite parallel thyristor voltage regulating and speed regulating circuits connected in series between the power supply and the controlled motor. Use the electronic switching characteristics of the thyristor. The degree of conduction of the thyristor is changed by controlling the trigger pulse and the firing angle by the single-chip microcomputer in the starter. Thereby completing the starting process.
2 Starting effect and advantages After the setting and debugging, the centrifuge starts smoothly, the starting time is less than 40 8, the production process meets the requirements of the production process, the starting current does not exceed 800 A, the impact on the power supply system is small, and the starting effect is good.
Soft starters have the following advantages over conventional auto-coupled buck starters:
(1) The soft starter fundamentally solves the impact of the instantaneous current spike generated by the auto-coupled buck starter by switching the voltage of the contactor to achieve the purpose of step-down. It is a non-contact control device, and there is no contactor belt. The load is switched, causing the contact arc to burn out.
(2) Limit line voltage drop and reduce current peak during start-up.
(3) Depending on the load, a variety of starting and stopping modes can be selected. A single soft starter can start multiple motors at different times, and the motor can achieve energy-saving operation when lightly loaded. In addition, the soft starter also provides functions such as overload protection, phase loss, rotor stall and other monitoring protection and rapid diagnosis of fault information.
3 Soft starter operation mode improvement and use should pay attention to Use the above wiring method to start and drag the centrifuge, the soft starter is always in working state. This is not conducive to fault repair and shortens the life of the soft starter. In order to facilitate maintenance and extend the service life. It is conceivable to add an isolation contactor at the lower end of the soft starter, and connect the contactor (K) or the bypass contactor at both ends of the two isolation contactors as shown in Fig. 2. When the soft starter is started.
The bypass contactor (K) is turned on, the isolating contactor at both ends of the soft starter is disconnected, and the soft starter is cut off, thereby achieving the purpose of convenient maintenance and prolonging the service life. If the motor needs to be stopped, the bypass contactor (K) can be directly disconnected, but this operation is easy to burn out the bypass contactor contact, and it is possible to consider switching to the soft starter and stopping by the soft starter. The soft starter only operates during start and stop, which in turn reduces harmonic pollution to the grid due to long-term operation of the soft starter.
When using the soft starter, it should be noted that in addition to its rated parameters, the main reason is that the environment is very clean and dry, which can eliminate the electrical fault caused by dust and moisture. In practical applications, the SCR fuse is blown due to large environmental dust and tidal temperature, and the soft starter cannot work. Followed by the ambient temperature and humidity, the operating temperature must be maintained between 0 ° C and 50 ° C, the device does not condense in the soft starter. In addition, when installing the soft starter, there should be enough space above and below it to facilitate heat dissipation. At the same time, it should be noted that when the overheating relay is also installed in the same chassis, a partition should be placed around the relay. In order to prevent the strong cold air flow from directly blowing onto the relay, the effective protection function is lost.
4 Conclusion The soft starter successfully activated the centrifuge, which is the starting of high-power motors and the dragging of heavy-duty equipment. Found a better way. It is worth promoting and learning. When the soft starter is selected and used, it must be strictly in accordance with the production process requirements and installation conditions, so that the soft starter can be used economically and prolonged.
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