A chemical company's chemical operation, monitoring, and control all use DCS systems. It is very important to provide DCS systems with high-quality, safe and reliable power supplies. The plant uses UPS to supply power to the DCS system. The UPS system consists of rectifier module, charging module, battery, inverter module, automatic bypass switch and manual maintenance bypass switch. UPS can provide DCS with high quality, safe and reliable power supply. Ensure that chemical production is safe, stable, and reliable.
The working principle of the UPS system: The factory power supply with poor power supply quality is first converted into a DC power supply by a rectifier device, all the way through the charging module to charge the battery, and the other channel is re-applied in the inverter device using a high frequency pulse width modulation (SPWM) method. Turn the DC power supply into a pure, high quality sine wave power supply to the load. When the AC working power disappears or the rectifier and other components fail, the battery pack supplies power to the inverter through the battery switch. When the fault output voltage of the inverter device is abnormal or overloaded, the automatic bypass switch is switched to supply power directly from the factory to the load.
The plant has a relatively small number of input and output points for the DCS system. It uses a dual AC line incoming single UPS power supply, and has a large number of input and output points for the DCS system. It uses a dual AC inlet and double UPS parallel power supply.
1. Dual AC Incoming Line Single UPS Connections Two AC Incoming Lines Single UPS Power Supply Connections are shown in Figure 1. In the figure, under normal conditions, the AC input is supplied to the UPS. When the AC input 1 is faulty, it is automatically switched to the AC input. 2 Supply power to the UPS. The AC power supply 1 and 2 are circuit interlocked. Under the normal working state of the UPS, it operates according to the operating mode of "AC input 1 - rectification - inverter - load"; when the rectifier module is faulty, it operates according to the "battery-inverter-load" operating mode; when the battery is discharged Automatically switch to the load directly from the automatic bypass switch to the AC; when the inverter module is faulty, according to the "AC input 1 - automatic bypass switch - load" mode of operation directly to the load for plant power; when the UPS has When serious faults need to be repaired or replaced, use the operating mode of “AC input 1—manual maintenance bypass switch†to supply power to the load. At this time, the UPS is short-circuited and can be overhauled or replaced without affecting the load. Normal power supply.
2. Dual AC inlet and double UPS parallel power supply mode Dual AC inlet and double UPS parallel power supply is shown in Figure 2. The output of two UPSs with the same power is directly connected in parallel, and the output of two UPSs is required to be connected in parallel. The voltage is the same, the frequency is the same, the phase is the same, and the load current carried is basically balanced. In the normal operation of the dual UPS parallel system, the two UPSs each have 1/2 of the load current, and if one UPS fails, the other will have all the loads, but the load must be reduced. The average no-failure time of the parallel UPS system is 7-8 times that of the stand-alone system, which greatly improves the reliability of the system. However, the control between the two UPSs of the dual UPS parallel system has a certain connection. When operating, be sure to clarify the control logic of the parallel board. Otherwise, the output voltage may sag due to the misjudgment of the board and the incorrect judgment of the board. The load has an adverse effect.
3. Precautions for using UPS (1) The UPS should have a certain margin on the options. For example, if the load is 4KVA, the UPS should be configured with more than 5KVA.
(2) The UPS should avoid frequent opening and shutting down, and it is better to turn on the power for a long time.
(3) The newly purchased UPS should be charged and discharged, which is conducive to extending the service life of the UPS battery. Normally, constant voltage charging is used. The initial charging current should not exceed 0.5*C5 ampere (C5 can be calculated with the rated capacity of the battery). The voltage of each battery is controlled at 2.30~2.35V to avoid damage to the battery. The charging current is constant for 3 hours, which proves that the battery is sufficient and the normal charging time is 12 to 24 hours.
(4) If the plant power supply is normal, the UPS will not have the opportunity to work. The battery may be damaged in the long-term floating state. The UPS should be charged and discharged periodically. This will not only activate the battery, but also check whether the UPS is working properly. status.
(5) Regularly check the UPS and check the float voltage once a month. If the float voltage is less than 2.2V, the battery should be charged in a balanced manner.
(6) Always wipe the battery with a soft cloth to keep the battery surface clean.
(7) Temperature control during UPS operation, because the temperature range of the UPS during operation is controlled within 20°C to 25°C to prolong the service life of the UPS battery. In an air-conditioned environment, temperature control of the UPS is particularly important.
(8) The UPS should be charged immediately after use to restore the battery to its normal state.
(9) The distance between the external battery pack and the UPS should be as short as possible, and the cross-sectional area of ​​the wire should be as large as possible to increase the conduction of the wire and reduce the power loss on the line. Especially when working with large current, the loss on the line should not be ignored. .
4. Routine Maintenance and General Troubleshooting of UPS 4.1 Routine Maintenance (1) Check the UPS operation display every day to confirm whether the UPS power supply running status is in normal operation.
(2) Use the ear to hear if the UPS power supply is abnormally sounding, mainly the power module and the cooling fan of the isolated output transformer, and whether the transformer has abnormal vibration sound.
(3) Check whether the outlet of the UPS power supply is blocked.
(4) Check the battery's float voltage, UPS's output voltage, and current every week on the UPS power supply's display screen, and make a good record. Compare with previous data. If the data change is relatively large, the cause should be promptly identified.
4.2 General Troubleshooting When the UPS power supply alarm occurs during operation, do not panic to operate any switch or button of the UPS, so as not to expand the accident or even cause the UPS output to be interrupted. When an alarm occurs on the UPS power supply, you should first read the status indicator on the display panel and the LCD screen prompts. The UPS has a self-diagnostic function. In the event of a failure, it will provide information such as the type of fault and the time of failure through the status indicator and the LCD screen. After seeing the status indicator and the LCD screen to indicate the type of fault, perform corresponding processing according to different types of faults. During the operation of the UPS, the following types of failures often occur.
(1) AC power failure, that is, AC input power failure or large-scale fluctuations. When this alarm occurs on the UPS, a battery discharge alarm message also occurs. At this time, the AC input light of the UPS panel status indicator is extinguished and the battery discharge lamp is on. . The treatment method must first determine whether the AC power supply fails, and check whether the UPS input switch trips and whether the fuse is blown. If it is indeed a power failure in the plant, if the recovery time is not known, remove the unimportant load to ensure uninterrupted power supply for important loads.
(2) Inverter failure. At the same time when this alarm occurs, the automatic bypass switch carries an on-board alarm. First, confirm whether the inverter overload alarm occurs on the panel. If yes, check the output current on the LCD screen. If the rated current is exceeded, turn off the unimportant load until the output current is less than the rated output current. Then press the reset key to cancel the alarm and restart the inverter and output. If there is no overload alarm signal, it means that the inverter is not shut down due to the inrush current, but the IGBT device or the drive control is faulty, and the manufacturer should be promptly notified for maintenance.
(3) When the bypass fails, when the alarm signal appears, the inverter asynchronous alarm signal should generally appear at the same time. This indicates that the input plant power supply voltage and frequency are out of the set range, but meet the requirements of the rectifier. At this time, the inverter starts to oscillate and does not follow the bypass. At this time, it is no longer possible to start a large-capacity load so as not to hit the inverter.
5. Concluding remarks As long as the UPS power supply is configured properly, daily attention is paid to maintenance and maintenance, so that the UPS can be operated stably and reliably so that it can supply DCS system with safe, reliable and high-quality power to ensure the safety of chemical production. Steady, long-term operation.
The working principle of the UPS system: The factory power supply with poor power supply quality is first converted into a DC power supply by a rectifier device, all the way through the charging module to charge the battery, and the other channel is re-applied in the inverter device using a high frequency pulse width modulation (SPWM) method. Turn the DC power supply into a pure, high quality sine wave power supply to the load. When the AC working power disappears or the rectifier and other components fail, the battery pack supplies power to the inverter through the battery switch. When the fault output voltage of the inverter device is abnormal or overloaded, the automatic bypass switch is switched to supply power directly from the factory to the load.
The plant has a relatively small number of input and output points for the DCS system. It uses a dual AC line incoming single UPS power supply, and has a large number of input and output points for the DCS system. It uses a dual AC inlet and double UPS parallel power supply.
1. Dual AC Incoming Line Single UPS Connections Two AC Incoming Lines Single UPS Power Supply Connections are shown in Figure 1. In the figure, under normal conditions, the AC input is supplied to the UPS. When the AC input 1 is faulty, it is automatically switched to the AC input. 2 Supply power to the UPS. The AC power supply 1 and 2 are circuit interlocked. Under the normal working state of the UPS, it operates according to the operating mode of "AC input 1 - rectification - inverter - load"; when the rectifier module is faulty, it operates according to the "battery-inverter-load" operating mode; when the battery is discharged Automatically switch to the load directly from the automatic bypass switch to the AC; when the inverter module is faulty, according to the "AC input 1 - automatic bypass switch - load" mode of operation directly to the load for plant power; when the UPS has When serious faults need to be repaired or replaced, use the operating mode of “AC input 1—manual maintenance bypass switch†to supply power to the load. At this time, the UPS is short-circuited and can be overhauled or replaced without affecting the load. Normal power supply.
2. Dual AC inlet and double UPS parallel power supply mode Dual AC inlet and double UPS parallel power supply is shown in Figure 2. The output of two UPSs with the same power is directly connected in parallel, and the output of two UPSs is required to be connected in parallel. The voltage is the same, the frequency is the same, the phase is the same, and the load current carried is basically balanced. In the normal operation of the dual UPS parallel system, the two UPSs each have 1/2 of the load current, and if one UPS fails, the other will have all the loads, but the load must be reduced. The average no-failure time of the parallel UPS system is 7-8 times that of the stand-alone system, which greatly improves the reliability of the system. However, the control between the two UPSs of the dual UPS parallel system has a certain connection. When operating, be sure to clarify the control logic of the parallel board. Otherwise, the output voltage may sag due to the misjudgment of the board and the incorrect judgment of the board. The load has an adverse effect.
3. Precautions for using UPS (1) The UPS should have a certain margin on the options. For example, if the load is 4KVA, the UPS should be configured with more than 5KVA.
(2) The UPS should avoid frequent opening and shutting down, and it is better to turn on the power for a long time.
(3) The newly purchased UPS should be charged and discharged, which is conducive to extending the service life of the UPS battery. Normally, constant voltage charging is used. The initial charging current should not exceed 0.5*C5 ampere (C5 can be calculated with the rated capacity of the battery). The voltage of each battery is controlled at 2.30~2.35V to avoid damage to the battery. The charging current is constant for 3 hours, which proves that the battery is sufficient and the normal charging time is 12 to 24 hours.
(4) If the plant power supply is normal, the UPS will not have the opportunity to work. The battery may be damaged in the long-term floating state. The UPS should be charged and discharged periodically. This will not only activate the battery, but also check whether the UPS is working properly. status.
(5) Regularly check the UPS and check the float voltage once a month. If the float voltage is less than 2.2V, the battery should be charged in a balanced manner.
(6) Always wipe the battery with a soft cloth to keep the battery surface clean.
(7) Temperature control during UPS operation, because the temperature range of the UPS during operation is controlled within 20°C to 25°C to prolong the service life of the UPS battery. In an air-conditioned environment, temperature control of the UPS is particularly important.
(8) The UPS should be charged immediately after use to restore the battery to its normal state.
(9) The distance between the external battery pack and the UPS should be as short as possible, and the cross-sectional area of ​​the wire should be as large as possible to increase the conduction of the wire and reduce the power loss on the line. Especially when working with large current, the loss on the line should not be ignored. .
4. Routine Maintenance and General Troubleshooting of UPS 4.1 Routine Maintenance (1) Check the UPS operation display every day to confirm whether the UPS power supply running status is in normal operation.
(2) Use the ear to hear if the UPS power supply is abnormally sounding, mainly the power module and the cooling fan of the isolated output transformer, and whether the transformer has abnormal vibration sound.
(3) Check whether the outlet of the UPS power supply is blocked.
(4) Check the battery's float voltage, UPS's output voltage, and current every week on the UPS power supply's display screen, and make a good record. Compare with previous data. If the data change is relatively large, the cause should be promptly identified.
4.2 General Troubleshooting When the UPS power supply alarm occurs during operation, do not panic to operate any switch or button of the UPS, so as not to expand the accident or even cause the UPS output to be interrupted. When an alarm occurs on the UPS power supply, you should first read the status indicator on the display panel and the LCD screen prompts. The UPS has a self-diagnostic function. In the event of a failure, it will provide information such as the type of fault and the time of failure through the status indicator and the LCD screen. After seeing the status indicator and the LCD screen to indicate the type of fault, perform corresponding processing according to different types of faults. During the operation of the UPS, the following types of failures often occur.
(1) AC power failure, that is, AC input power failure or large-scale fluctuations. When this alarm occurs on the UPS, a battery discharge alarm message also occurs. At this time, the AC input light of the UPS panel status indicator is extinguished and the battery discharge lamp is on. . The treatment method must first determine whether the AC power supply fails, and check whether the UPS input switch trips and whether the fuse is blown. If it is indeed a power failure in the plant, if the recovery time is not known, remove the unimportant load to ensure uninterrupted power supply for important loads.
(2) Inverter failure. At the same time when this alarm occurs, the automatic bypass switch carries an on-board alarm. First, confirm whether the inverter overload alarm occurs on the panel. If yes, check the output current on the LCD screen. If the rated current is exceeded, turn off the unimportant load until the output current is less than the rated output current. Then press the reset key to cancel the alarm and restart the inverter and output. If there is no overload alarm signal, it means that the inverter is not shut down due to the inrush current, but the IGBT device or the drive control is faulty, and the manufacturer should be promptly notified for maintenance.
(3) When the bypass fails, when the alarm signal appears, the inverter asynchronous alarm signal should generally appear at the same time. This indicates that the input plant power supply voltage and frequency are out of the set range, but meet the requirements of the rectifier. At this time, the inverter starts to oscillate and does not follow the bypass. At this time, it is no longer possible to start a large-capacity load so as not to hit the inverter.
5. Concluding remarks As long as the UPS power supply is configured properly, daily attention is paid to maintenance and maintenance, so that the UPS can be operated stably and reliably so that it can supply DCS system with safe, reliable and high-quality power to ensure the safety of chemical production. Steady, long-term operation.
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