UPS power supply principle

UPS is mainly composed of rectification and filtering circuit, charger, inverter, output transformer and filter, static switch, battery pack and control, monitoring, display alarm and protection circuit.

When the mains power is normal, the input voltage passes through the rectification and filtering circuit, all the way to provide voltage to the inverter, and all the way to the charger to charge the battery. At this time, the static switch is switched to the inverter side, and the inverter completes the functions of voltage regulation and frequency tracking.

When the mains fails, the UPS works in the backup state, and the static switch is still switched on the inverter side. The inverter converts the DC voltage of the battery into an AC voltage, and outputs it to the load through the static switch.

When the mains is normal, the inverter fails or the output is overloaded, the UPS works in the bypass state, and the static switch switches to the mains terminal, and the mains directly supplies power to the load.

4 elements of UPS

The four elements of a high-availability UPS: reliability, functionality, availability, and fault tolerance.

Reliability: UPS modules, static switches and power distribution equipment must be very reliable, measured by MTBF, and the system equipment should be as simple as possible to minimize single point failures.

Functionality: It should be able to protect the load from all mains power interference, and the interference that UPS of different technologies can protect is different.

Availability: Simultaneous maintenance must be allowed for all power supplies in the system. When some components of the system are maintained, the system can still supply power to the load normally. True maintainability is related to the redundancy of the system, but the system should have internal or external maintenance bypass.

Fault tolerance: The system must be fault tolerant to handle the failure of system components without affecting the power supply to the load equipment.

Reliability and functionality mainly depend on the internal technology of the UPS, that is, technologies such as passive standby, line interactive, and double onversion are used.

Availability and fault tolerance mainly depend on UPS redundancy method and power distribution circuit scheme

UPS classification

Commonly used UPS systems are generally divided into two categories: standby redundant systems and parallel redundant systems.

In the backup redundant system, one power supply unit supplies power, and several other units are in standby. Once the running power supply unit fails, the backup power supply unit will be put into operation immediately.

In a parallel redundant system, multiple power supply units are connected in parallel to supply power. Under normal working conditions, the output power of each power supply unit is lower than its rated output power.