8. After the UPS uninterruptible power supply is turned on and works for a period of time, the buzzer beeps long and there is no output. If the UPS can work for a period of time, it indicates that its basic circuit is normal, which may be due to some kind of protection. There are two main reasons for this:
(1) The control circuit for the conversion of mains/inverter power supply has malfunctioned, resulting in unstable operation of the voltage comparison amplifier;
(2) The working point drift of the overcurrent protection circuit causes misoperation.
Two easily confused concepts
When it comes to power systems, we often mention another term: EPS. What is the difference between EPS and UPS? In fact, EPS stands for Emergency Power Supply in English, which can be translated as emergency power supply. It is an important component of modern building safety facilities. Due to the similarities in application between EPS and UPS, there may be some confusion. Here is a brief introduction to the main differences between EPS and UPS: Firstly, the scope of use of EPS and UPS is different. The development of EPS originated from the need to ensure power security and fire protection linkage in the event of a sudden power grid failure. EPS can provide instant escape lighting and fire emergency, protecting users’ lives or bodies from harm. Its product technology requirements are subject to the supervision of the Ministry of Public Security’s fire certification and accept on-site fire safety acceptance. However, UPS is only used to protect user devices or businesses from economic losses, and its product technology requirements are certified by the Ministry of Information Industry. The security standards applicable to the two are clearly different. Secondly, the power supply objects of UPS are computers and network equipment, and the load properties (input power factor) are not significantly different, so the national standard stipulates that the output power of UPS is 0.8. The power supply objects of EPS are power guarantee and fire safety. If the load properties are inductive, capacitive, and rectifier nonlinear loads, the output power factor cannot be set to 0.8. Moreover, the load is only put into operation after the mains power is cut off, so EPS is required to provide a large impulse current. EPS needs to have good output dynamic characteristics and stronger overload resistance. The technical design indicators of EPS and UPS components are allocated differently. In short, we can simply understand that the load of EPS is only put into operation after a power outage in the city, and it does not have high requirements for the quality of power supply, mainly providing emergency electricity; UPS plays a corresponding role in both normal and abnormal power supply, and its power quality is significantly higher than EPS. It can provide clean, safe, and reliable power supply for precision electronic equipment.