I. Core definition
Power frequency on-line UPS: adopts power frequency transformer isolation, dual-conversion pure on-line architecture, keeps the voltage and frequency stable throughout the process, and the power supply/power failure is continuously carried by the inverter, which is the mainstream model of industry, computer room and precision equipment.
Core features: transformer isolation, strong surge resistance, impact resistance, three-phase majority and high reliability.
Second, the overall four core components
Rectifier (AC→DC)
accumulator battery
Power frequency inverter (DC→AC)
Static bypass switch+manual maintenance bypass
Three working modes (the most critical)
Mode 1: Normal commercial power (normal inverter mode)
Full-range on-line double conversion work
Three-phase/single-phase mains input → into rectifier
Rectification converts alternating current into stable direct current.
Direct current charges the battery all the way to keep the battery fully charged.
The direct current is sent to the power frequency inverter, which is converted into pure sinusoidal alternating current with stable voltage and frequency.
After being filtered, isolated and stabilized by a power frequency isolation transformer
Direct uninterrupted supply of back-end load
Key points: the commercial power never directly supplies power to the load, and the load is supplied by the inverter all the time, so the voltage frequency is always stable.
Mode 2: Power outage/abnormality (battery inverter mode)
Power outage, under-voltage, over-voltage, lack of phase and frequency exceeding the standard.
Rectifier stops working, zero switching.
The battery immediately discharges and outputs direct current.
Direct current is directly sent to the inverter, and continues to reverse into standard alternating current load.
The load has no power failure and no perception at all.
The discharge time is determined by the battery capacity.
Mode 3: Bypass Power Supply Mode (Fault/Repair)
Automatic switching in case of inverter failure, overload, overheating and maintenance.
The commercial power directly supplies power to the load through static bypass without rectification and inversion.
Features: Keep the load without stopping, but lose the protection of voltage stabilization, purification and power failure.
When maintaining, close the manual maintenance bypass, which can completely cut off the power and repair the UPS host.
Fourth, the power frequency machine is unique: the function of power frequency transformer (different from high frequency machine)
Electrical isolation: isolate the interference of neutral wire and ground wire and common-mode interference of commercial power.
Strong voltage stabilization: wide voltage input and stable output.
Anti-impact load: the motor, air compressor and water pump can easily bear the heavy current when starting.
Lightning protection and surge prevention: the high voltage peak of power grid is blocked by transformer.
The output waveform is purer, and it is the first choice for medical, industrial and precision instruments.
V. complete energy flow direction
Commercial power is normal.
Commercial power → rectification (AC→DC) → inverter (DC→AC) → power frequency transformer → load.
Parallel branch: rectification → battery charging
Power outage
Battery discharge (DC) → inverter → power frequency transformer → load
Bypass state
Mains → Static Bypass → Load
Sixth, the principle of voltage and frequency stabilization
Voltage stabilization: PWM pulse width modulation inside the inverter can adjust the output voltage amplitude in real time.
Frequency stabilization: the inverter oscillates independently, and the output frequency is not affected by the mains frequency.
No matter whether the mains voltage fluctuates, the output will always be 220V/380V 50Hz.
Seven, switching logic (zero switching)
The normal state of on-line UPS is inverter, and the power failure only cuts off the rectifier and connects the battery.
When the switching time is less than 2 ms, computers, servers and industrial control equipment will not be restarted at all.
Advantages and disadvantages of power frequency online UPS
advantage
Strong isolation, the first choice in harsh environment of power grid.
Strong loading capacity, compatible with inductive, resistive and dynamic loads.
Anti-lightning, anti-harmonic, anti-grid distortion
Low failure rate and durable industrial scene.
The output power quality is the highest
disadvantage
Large volume and heavy weight (built-in power frequency transformer)
The efficiency is slightly lower than that of high frequency machine.
Higher prices
Nine, application scenarios
Industrial production line, PLC industrial control, medical equipment, server room, fire emergency, precision instruments, outdoor power grid poor areas, high-power backup power supply.
