How to efficiently maintain your UPS inverter?

To ensure that the UPS inverter power supply works in the optimal running state for a long time and discover possible faults in time to prevent the expansion of potential faults, ensure the power supply security of the data center, and improve the utilization rate of the UPS inverter power supply, you must ensure that the UPS works in a proper working environment and do a good job in routine and periodic maintenance.

01 High-risk inspection Guide

UPS system inspection

• Check whether the UPS input and output switches are in the closing state and whether the closing indicator is on;

• Check whether the buzzer of the UPS system generates an audible alarm and other abnormal noises occur in the system.

• Check whether the noise emitted by the UPS inverter power supply changes significantly or is abnormal.

• Check whether all display units on the UPS control panel are in normal operating state, whether the operating parameters are within the normal range, and whether there is any fault and alarm information in the displayed records;

• In particular, check the three-phase output current of the UPS inverter module. If the output current value is found to deviate significantly from the original normal value, the external load should be identified. Attention should be paid to whether there is a large nonlinear load and large inductive load access;

• Check whether the temperature and humidity values of the UPS and battery rooms are within the specified range;

• Check the fan running status in the UPS cabinet and whether the air filter is blocked.

• Check the UPS internal capacitor components for anomalies, local hot spots, liquid leakage, bulge, and odor.

• Check whether the wiring terminals, cables and copper bars are overheated, damaged and securely connected;

• Check whether the input and output status and parameters of a single UPS in the monitoring system are normal (including input voltage, output voltage, output current sharing, load rate, etc.).

• Check whether the status of the parallel UPS system and output parameters in the monitoring system are normal (including output voltage, output current sharing, load rate, and PF value).

• Check whether the battery switch is in the closed state;

• Check whether the current setting of the battery switch is consistent with the actual operating load rate;

• Check whether the connection point of the battery pack has obvious overheating phenomenon, check whether the contact is tight, there is no oxidation;

• Check the battery for abnormalities, including battery cleanliness, deformation, bulging, and leakage. Battery room has no odor, abnormal sound and so on.

Inspect the front and rear PDC

• Check whether the power distribution cabinet is switched off. Some bypass switches are switched off.

• Check whether the current and time setting values of the UPS input and output switches on the power distribution cabinet are consistent with the actual operating conditions.

• Check whether the PDC indicators blink abnormally, whether there is abnormal sound, and whether there are local hot spots in the cabinet.

• Check whether the automatic energy storage control switch of each circuit breaker is in the automatic position, and check whether the switch state has energy storage;

• Check whether the voltage, current, power and other readings of each distribution cabinet instrument are displayed normally, whether the values are kept within the set range, and whether the parameter setting values of each circuit breaker are consistent with the design values;

• Check whether the core power supply loop parameters (voltage, current, power factor, and frequency) of the capacitor compensation cabinet are within the normal range, whether the capacitor in the cabinet has protrusions or liquid leakage, and whether the capacitor and other components have local hot spots.

02 Functional Detection

• Check the UPS input power quality (including input voltage and input frequency) and output power quality (including output voltage, output frequency, and output waveform distortion).

• Check whether the power failure time is shorter than the specified value when the UPS inverter power is switched over.

• Check whether the instantaneous output voltage drop is smaller than the specified value when the UPS inverter power is switched over.

• Check whether the UPS output harmonic distortion rate is smaller than the specified value.

• Check whether the floating charging voltage and charging current value of the battery pack are within the design range;

• Check whether the battery string voltage and battery voltage are within the normal range.

• Check the battery string backup time, turn off the main input switch, and before the battery voltage drops to the discharge termination voltage, turn on the input switch, and record the UPS backup battery room.

• Check whether the battery pack has the characteristics of high current output at startup;

• Check the internal resistance of the battery string. If the internal resistance exceeds the specified value, discharge the battery string after balanced charge or activate it.

• Check whether the front and rear PDC circuit breakers are manually disconnected properly.

03 Simulated fault check

• Simulate the mains input power failure and observe the UPS working mode switchover process.

• Simulate the mains input power failure, and record the UPS battery voltage curve with the discharge time.

• Simulate the mains input power failure and the battery string stops working under voltage, and observe the UPS operating status after the mains is restored;

• Simulate a UPS fault and check whether the UPS bypass power supply is normal for a long time.

04 Precautions for battery management and maintenance

In order to improve the utilization rate of the battery as far as possible, make it as close to the design life as possible, reduce the reinvestment of equipment capital, the following three points should be paid attention to in the use and maintenance process of lead-acid maintenance-free battery:

Note that the ambient temperature of the UPS inverter power supply and its backup battery string should not exceed 30 ° C. When the ambient temperature of the battery exceeds 35 ° C, the storage life of the battery is shortened due to increased internal battery loss. On the contrary, when the ambient temperature is low, the actual capacity of the battery will decrease due to the particularity of the temperature of the electrolyte inside the battery. When the ambient temperature is 0 ° C, the output capacity of sealed lead-acid batteries is about 80% of the nominal value.

The second is deep discharge. There is a specified relationship between the discharge termination voltage of a sealed lead-acid battery and its discharge current. If the battery is discharged at a 10-hour discharge rate, that is, the current discharge of 1/10 of the nominal capacity of the battery, the discharge voltage should be stopped when the specified discharge voltage to 1.8, if the battery continues to discharge at this time, when the voltage of the battery is too low, the above phenomenon of over-discharge occurs, that is, deep discharge. Deep discharge of sealed lead-acid battery will inevitably reduce the number of effective cycles and shorten the battery life. If the deep discharge can not be timely charging will accelerate the early failure of the battery.

The UPS inverter battery management system usually has the function of battery pack discharge termination voltage protection. In the intelligent battery management system, the protection point of the battery generation termination voltage is automatically adjusted with the discharge current of the battery. In this way, the actual protection point of the battery discharge termination voltage is higher than the specified protection point of the battery when the output load changes in real time during the discharge time. In this way, the energy of the backup battery pack can be fully utilized without causing the battery to enter the harmful state of deep discharge.

The third is to regularly carry out necessary maintenance on the battery bank. The maintenance of spare batteries can be divided into initial maintenance for new batteries and regular maintenance for batteries that are in use or stored for a long time. After connecting the battery string to the UPS inverter power supply, the UPS inverter power supply can run with no load. You can set the charging current at the 10-hour charging rate for the standby battery string. It is recommended that the ambient temperature be kept at about 25 ° C, and charge the standby battery string for 8-10 hours according to the floating charging voltage provided in the product instructions. After the battery is charged, put the battery in a static position for about 2 hours. Transfer the UPS inverter power to the standby battery string for running, and put an appropriate load on the output end to ensure that the output current of the battery string reaches 0.1C to 0.2C. Set the discharge termination voltage at 1.8V for each cell. After a charge and discharge cycle, on the one hand, it can observe whether the charge and discharge performance of the battery is normal, on the other hand, it can make the initial capacity of the new battery close to its nominal capacity. After that, the standby battery pack can be recharged to officially put into standby state.

Perform regular maintenance on the battery string that is connected to the UPS inverter or is idle. Periodic maintenance includes the following aspects: First, periodically discharge and charge the battery string in the long-term standby floating charge state. Charge and discharge time interval is generally 6 ~ 12 months, because the lead-acid battery does not exist memory effect, so the capacity of the release does not have to be equal to the nominal capacity, the general release of the nominal capacity of 10% ~ 20%. When the backup battery string of the UPS inverter is regularly charged, take reliable measures to turn off the UPS input rectifier switch to discharge the battery. Ensure that the load does not interrupt the power supply during the battery string discharge maintenance. For some loads with a short power retention time, you can use the UPS inverter with the battery self-check function to self-check the backup battery string for regular charge and discharge maintenance. The UPS inverter with this advanced function does not need to disconnect the output of its internal AC/DC rectifier. Instead, the DC output voltage of the rectifier is adjusted so that the rectifier and the backup battery pack can supply power to the DC/AC positive basalt inverter in parallel. The output voltage of the rectifier is adjusted by the detection control circuit to discharge the standby battery pack at a constant current. In addition, the UPS inverter displays the remaining battery string capacity at any time. During this operation, if the battery discharge fails due to the damage of the last battery in the battery pack, the output voltage of the rectifier immediately rises to the normal working state to ensure the normal input of the sine wave inverter, so that the load can get continuous uninterrupted power supply. When the battery self-check function is used for discharge maintenance, the energy released is generally controlled between 10% and 20%.

Another type of maintenance for a backup battery pack is a short balanced charge of the battery pack. This is because the end voltage and internal resistance of the battery pack will be inconsistent due to internal reasons in the state of floating charge and reserve for a long time or after repeated use. In order to eliminate the hidden trouble of this unbalanced phenomenon, the individual voltage of each battery can be charged to 2.3V ~ 2.4V during balanced charging, and the charging current should be limited to 0.2C. In this balanced charging state for about 5 hours, it will be transferred to the normal floating charging state. Maintain the balanced charge of sealed lead-acid batteries when the ambient temperature is 20 ° C to 25 ° C. When to balance the charge of sealed lead-acid batteries depends on the actual battery usage. Generally, the imbalance of voltage and internal resistance in the battery pack can be improved and the service life of the battery pack can be extended after balanced charging.