3 minutes to understand, UPS uninterruptible power supply, working principle and usage requirements
In some occasions with higher load level requirements (Class 1 load), the commonly used power supply is UPS uninterruptible power supply, that is, equipment that cannot be powered off, such as communication systems; computer systems; monitoring systems; DCS systems; operating rooms in medical systems; important electric valves in the industry, etc. Nowadays, UPS uninterruptible power supply sockets are also commonly used in hospital wards and hotels. It can be said that UPS is used more and more widely. As electrical practitioners, we You should understand the working principle, operation method and simple troubleshooting of UPS. This article briefly introduces the composition and working principle of UPS, and the operation and troubleshooting methods of UPS will be introduced later.
UPS composition and working principle
UPS generally consists of rectifier, battery, inverter, static switch and control system composition. The online UPS is usually used. It first converts the AC power input from the mains into a regulated DC power supply, supplies the battery and inverter, and then becomes a stable, pure, and high-quality AC power supply through the inverter. It can completely eliminate any power problems (voltage fluctuations, frequency fluctuations, harmonic distortion and various interferences) that may occur in the input power supply. Its working principle block diagram is shown in the figure
Composition and working principle
New UPS uninterruptible power supply The functional requirements of
1. The switching time of the static bypass switch is generally 2~10ms, and should have the following functions:
a. When the inverter device fails or needs maintenance, it should be switched to the grid (mains standby) power supply in time.
b. When the branch circuit suddenly fails and the current exceeds the predetermined value, it should be switched to the grid (city standby) power supply to increase the short-circuit current and make the protection device act quickly. After removing the fault, restart and return to the inverter for power supply.
c. The uninterruptible power supply device with frequency limiting link, when the grid frequency is passive or the voltage fluctuation exceeds the rated value, it should automatically disconnect from the grid, frequency and voltage It will automatically connect to the grid when it returns to normal.
2. When using the mains bypass, the frequency and phase of the inverter should be synchronized with the mains phase lock.
3. For the negative unbalance of the three-phase output, the difference between the fundamental rms current of the largest one-phase load and the smallest one-phase load should not exceed the uninterrupted 25% of the rated current of the power supply, and the maximum line current does not exceed its rated value.
4. The unbalance coefficient of the detected voltage of the three-phase output system (negative sequence component versus positive sequence The weight) should not exceed 5%. The total waveform distortion of the output voltage should not exceed 5% (10% allowed for single-phase output)