German BEINING UPS Power Supply: Four Operating Modes and Switching Principles
German BEINING UPS Power Supply: Four Operating Modes and Switching Principles
BEINING UPS systems (using the ENERTRONIC I series industrial UPS as an example) feature four distinct operating modes, each designed to handle different operating conditions. These modes are switched automatically or manually under the control logic of the system, ensuring continuity, stability, and power quality for the connected load. The following sections detail the principles, switching conditions, and technical specifics of each mode.
I. Normal Operating Mode (Mains Supply)
Working Principle
The normal operating mode is the most common operating condition for the UPS and represents the highest quality power supply path.
Three-phase mains power enters the UPS through the input terminals, first passing through an input isolation transformer (or autotransformer), then entering the rectifier. The rectifier employs an IGBT semiconductor rectifier bridge with power factor correction circuitry, converting AC power into an adjustable, stable DC voltage. During this process, the power factor correction circuit actively regulates the input current waveform to synchronize with the voltage waveform, achieving an input power factor above 0.99 and input current total harmonic distortion below five percent, producing virtually no harmonic pollution to the upstream grid.
The rectified DC power is split into two paths: one path feeds the inverter as its energy source; the other path float-charges the battery, keeping it at optimal state of charge. The rectifier is sized to simultaneously supply the inverter at full load and efficiently recharge a discharged battery—restoring a fully discharged battery to approximately ninety-five percent capacity within about twelve hours.
The inverter receives the DC power and, through IGBT power devices and sinusoidal pulse width modulation control, converts it into stable sine wave AC power with regulated amplitude and frequency. The output isolation transformer performs two critical functions in this process: electrical isolation and voltage matching, ultimately delivering clean, stable AC power to the load.
Switching Conditions
When mains voltage and frequency are within permissible ranges, the UPS continuously operates in this mode. The rectifier is equipped with a software-controlled soft-start function—after mains recovery, it does not immediately start at full power but gradually ramps up input current, avoiding current shock to the recently restored grid. In parallel systems, the restart of each UPS is staggered to prevent simultaneous startup from causing cumulative impact on the grid.
II. Battery Operating Mode
Working Principle
When mains voltage sags, is interrupted, or exceeds permissible tolerance ranges, the system automatically switches to battery operating mode.
At this point, the battery connected to the DC input automatically engages, directly supplying DC power to the inverter. The inverter continues converting DC power into pure sine wave AC power, which passes through the output isolation transformer to continuously supply the load. The entire switching process occurs without any interruption—voltage and frequency on the load side remain unaffected.
The battery discharge process is fully recorded by the system's event logger and triggers alarm signals, alerting operators that the system is currently operating on battery power. The system continuously monitors battery voltage; when voltage drops near the undervoltage protection threshold, it issues an advance undervoltage event message, providing operators with a time window to take countermeasures. If battery voltage reaches the final discharge termination voltage and mains power has not been restored, the inverter automatically shuts down to protect the battery from deep discharge damage.
Switching Conditions
Automatically triggered during mains failure, with no interruption during the transfer. It should be noted that the transfer from mains supply to battery supply, and from battery supply back to mains supply, is entirely automatic and requires no manual intervention.
In power system applications, BEINING UPS can draw power from the existing DC operation power system in a substation, sharing the battery bank with the station's DC system without requiring a separate battery configuration. This avoids redundant battery investment, reduces system maintenance workload, and lowers operating costs.
III. Static Bypass Operating Mode
Working Principle
The static bypass switch is a critical component of the UPS system, composed of microprocessor-controlled antiparallel thyristor power devices installed in the power bypass circuit.
When inverter output exceeds preset tolerance ranges or cannot supply power normally due to a fault, the static bypass switch automatically transfers the load to bypass mains supply. The transfer is microprocessor-controlled, with no interruption to load power. The static bypass serves as the "last line of defense"—it ensures that even if the inverter fails, the load can still receive power from the mains, preventing complete power loss.
The microprocessor continuously monitors system status to prevent any unreasonable transfer requests that could cause system misoperation. Uninterrupted transfer is only permitted when the inverter voltage, frequency, and phase are fully synchronized with the bypass mains. Only under synchronous conditions is uninterrupted transfer allowed. When mains frequency deviation exceeds the preset permissible range, the uninterrupted transfer function is locked out—in this case, if the inverter fails, the transfer will occur with interruption.
The static bypass overload capacity is 150 percent for ten minutes, 120 percent for longer durations; under short circuit conditions, it can withstand 500 percent surge current for one hundred milliseconds, ensuring reliable tripping of downstream circuit breakers.
Switching Conditions
The following conditions trigger static bypass transfer:
Inverter output exceeds preset tolerance: Such as output voltage too high, too low, or waveform distortion exceeding permissible limits.
Inverter fault: Internal power device failure or control circuit abnormality.
Load overload: Load current exceeds inverter rated capacity and duration exceeds permissible limits.
Load short circuit: Short circuit fault occurs on the output side.
When the fault is cleared and the inverter returns to normal and stable operation, the system automatically transfers the load back to inverter supply without interruption. Even if the bypass mains is intentionally disconnected during testing, the system can still complete this automatic return transfer.
IV. Manual Maintenance Bypass Mode
Working Principle
Manual maintenance bypass is a power supply mode designed for maintenance and repair convenience. The UPS system integrates a manual maintenance bypass switch with a manual operating mechanism.
When comprehensive maintenance, repair, or module replacement is required for the UPS main unit, operators transfer the load to manual maintenance bypass. After transfer, the load is supplied directly by mains power, no longer passing through the UPS rectifier and inverter. The UPS main unit is completely electrically isolated from the load, allowing safe power-down maintenance or component replacement.
After maintenance is completed, the system can transfer back to normal operating mode without interruption, provided the inverter output is synchronized with the mains.
As an optional configuration, an external manual bypass cabinet can be provided. With external manual bypass, the entire UPS can be completely powered down, or even replaced while the load remains powered—this is invaluable for continuous process industries that cannot schedule production downtime for equipment maintenance.
Switching Conditions
Triggered manually by operators only during equipment maintenance, repair, or module replacement. This function allows on-site maintenance personnel to safely perform annual preventive maintenance, component replacement, or firmware upgrades without affecting critical load operation.
Comparison of the Four Operating Modes
| Operating Mode | Trigger Condition | Switching Characteristics | Load Power Source |
|---|---|---|---|
| Normal Operating Mode | Mains normal | — | Inverter (supplied via rectifier) |
| Battery Operating Mode | Mains failure or out of tolerance | Automatic, uninterrupted | Inverter (supplied via battery) |
| Static Bypass Mode | Inverter abnormality or overload | Automatic, uninterrupted when synchronized | Bypass mains |
| Manual Maintenance Bypass | Maintenance and repair needs | Manual operation | Bypass mains (direct) |
Additional Notes
The BEINING ENERTRONIC I series is designed to meet the highest UPS classification VFI SS 111, complying with IEC/EN 62040-3 standards. VFI stands for Voltage and Frequency Independent, meaning that output voltage and frequency are completely regenerated by the inverter, independent of any disturbances on the input side. Whether the mains experiences voltage sags, voltage swells, harmonic distortion, frequency drift, or complete blackout, the connected load always receives clean, stable, regulated sine wave power.
The coordinated operation of these four modes forms a complete power supply protection system: the normal operating mode ensures daily power quality, the battery operating mode handles mains interruptions, the static bypass handles inverter faults, and the manual maintenance bypass supports equipment maintenance—layer upon layer of defense, ensuring that critical loads receive reliable power under any operating condition.