Working principle of industrial frequency UPS power supply

The power frequency UPS employs an online double-conversion topology, relying on a power frequency transformer, SCR rectification, and IGBT inverter technology to achieve mtabilization, backup power during outages, and isolation from interference. Its operating principle aligns with the power supply requirements of industrial scenarios. The following analysis, using accessible technicge, explains the core working processes, three operating modes, and the functions of key components, facilitating understanding, commissioning, and maintenance for industrial technicians.

I. Core Working Phases (Normal Utility Power Status)

1. Rectification Phase: Utility power passes through the input filter module to remove interference nals such as harmonics and surges, entering the SCR rectifier module; the SCR rectifier module converts AC utility power into DC voltage, stabilizes the DC bus voltage, andes a stable DC power supply for the inverter phase; during the rectification process, the input side of the power frequency transformer operates synchronously to provide preliminary isolation and voltage rgulation.

2. Inversion Phase: DC voltage enters the IGBT inverter module, which converts DC power into pure sine wave AC power. The output transformer further stabilizes the voltage and achieveal isolation, ultimately providing a stable and pure power supply to industrial loads; meanwhile, a portion of the DC power output by the rectifier module charges the battery bank to ensure the batemains fully charged and ready for emergency power supply.

3. Monitoring and Protection Phase: The UPS is equipped with an intelligent monitoring module that monitors parameters such as input voltage, output voltge, current, and battery voltage in real-time. If abnormalities occur (such as voltage fluctuations or overloads), the protection mechanism is immediately triggered to ensure the safety of the UPS unit nd the load.

II. Three Working Modes (Adapting to Different Power Supply Scenarios)

1. Utility Mode (Normal Operating Mode): When utility voltage and frequency are within normal ranges (voltage ±30%, frequency 45-65Hz), the UPS converts utility power into stable power for the load via rectification and inversion stages while simultaneously charging the battery pack. During this time, the power frequency transformer operates continuously to provide isolation and voltage regulation.

2. Battery Mode (Emergency Power Supply Mode): In the event of a utility power outage or abnormal utility power (exceeding the UPS input range), the UPS immediately cuts off the utility input and switches to battery power mode. The battery pack releases DC power, which is converted into AC power by the inverter module and supplied to the load via the output transformer. The switching time is ≤10ms, ensuring uninterrupted operation of the load. At this time, the rectifier module stops working, while the inverter module operates in coordination with the battery pack and the output transformer.

3. Bypass Mode (Fault Emergency Mode): When the UPS main unit malfunctions (e.g., damage to the rectifier or inverter module) or the load experiences severe overload (exceeding 200% of rated load), the UPS automatically switches to bypass mode, directly supplying utility power to the load via the bypass switch to prevent load shutdown. Simultaneously, a fault alarm is triggered to alert technicians for timely maintenance. At this time, the output transformer stops working to ensure temporary power supply to the load.

III. Working Functions of Key Components.

1. Power Frequency Transformer: A core component that achieves electrical isolation between input and output, stabilizes output voltfers against overload impacts, and suppresses harmonics; it is the key distinction between power frequency UPS and high-frequency UPS;

2. SCR Rectifier Module: Converts AC utility to DC power, featuring strong resistance to current surges and adapting to load fluctuations in industrial scenarios;

3. IGBT Inverter Module: Converts DC power to sine wave AC power,ding a clean output waveform to ensure the normal operation of the load;

4. Battery Pack: The core of emergency power supply, providing power to the load during utility power outages, supg long-delay power supply, and compatible with various types such as lead-acid and lithium iron phosphate;

5. Monitoring and Protection Module: Monitors equipment operating parameters in real-timing multiple protection functions including overload, overvoltage, overcurrent, undervoltage, and short circuit protection to prevent equipment damage.