EPS power supply started out later than the generator and the UPS power supply, so most users did not know enough about it, so most of the users in the emergency power supply chose to use the generator and the UPS power as the main emergency power supply Way to achieve the function of EPS emergency power supply, but to provide emergency power supply capacity, both the generator and UPS power have exposed many shortcomings.
1) Diesel generator sets as the emergency power supply is currently used by most of the projects, is also the most common emergency backup power supply, due to the larger capacity of diesel generators, parallel operation and continuous power supply for a long time, so a long Application history. However, no matter how fast the generator starts, it takes at least 10 seconds to several minutes from when the generator receives a start signal after a power failure until the generator voltage and frequency reach a steady state for power supply. During this period , All electrical equipment are stopped working, it may cause damage to a few devices or the safety of life and property issues. The EPS startup generally does not exceed 25ms, so the normal working probability of affecting the device is very small. On the other hand, diesel generator applications in emergency power supply applications, there are many disadvantages, mainly:
(1) In high-rise buildings, diesel generator sets are generally placed in the basement and are designed with great difficulty and high cost. All the facilities equipped with air intake, cooling, smoke exhaust, vibration absorption and noise reduction need to be fully considered.
(2) There is a fire hazard. Its tank looks like a very dangerous "bomb" in the event of a mishap.
(3) Routine maintenance is frequent and heavy workload;
(4) diesel generator noise, produce pollution;
(5) There is a lot of sulfur dioxide in the exhaust smoke, causing serious pollution and affecting the environment. Take the load capacity of 200kW as an example, compare the cost performance of EPS with diesel generator set. EPS selection, the rated power and load power ratio of 1: 1 can be, the total price of about 600,000 yuan. The choice of diesel generator, the rated power and load power ratio should be 1.3 ~ 1.5: 1, 200kW load, diesel generator set needs 250kVA specifications, the unit price of 400,000 yuan, but in addition to the price of the unit itself , Plus the need for additional auxiliary device costs about 16 to 290,000 yuan, now 200,000 yuan, that is, the total cost of diesel generator set to 60 million. Therefore, the actual price of the two is almost the same. It is also not difficult to see that if EPS emergency power supply capacity is less than 200kW, the price is less than the overall cost of diesel generator sets. At present, the total load capacity of fire emergency power supply occasions is generally below 200kW. Considering the long-term interest of investment, EPS emergency power supply is much more economical than diesel generator sets.
2) EPS power from the principle and structure similar to the UPS. On-line UPS Regardless of whether the mains is normal, it is always powered by the inverter, that is, in the order of "mains input → rectification → inverter → output", and only bypassed when the inverter is faulty or overloaded Output. The EPS, when the city electricity is normal, electricity through the switch S output to the load, while the battery charger charger. When the control system detects a mains blackout, the inverter works, so that the switch S is switched to the inverter output state to provide power to the load. UPS is a double conversion structure of uninterruptible power supply, mainly for the load to provide stable high-quality power, not affected by mains power grid, and the conversion time is generally less than 10ms, so, UPS is widely used in computers, program-controlled switches , Medical equipment and precision electronic equipment can not interrupt the power supply place. However, UPS is not only responsible for emergency power supply, but also assume the task of improving the quality of power, so its inverter should be continuous work, the service life is relatively short, usually 5 to 8 years, especially the battery replacement is more frequently. On the other hand, UPS inverters have long been at work, their own loss, but also on the use of the environment demanding, can only be placed in the computer room or air-conditioned room. UPS is designed for the IT industry, computer and communications load design and load less than the EPS adaptive power supply, for example, if the emergency power supply occasions with inductive inductors such as AC induction load, then the UPS design selection and There will be a big problem in use. As the AC motor starting current is usually 5 to 7 times the rated current, while the UPS overload criteria: Overload 125%, A class is 10min, B class 1min, C class 30s; overload 150% 10s . If you want to UPS can withstand the impact of the motor starting current, it is bound to increase the rated capacity of the UPS, which undoubtedly requires more investment, but may not be able to completely solve the problem. Therefore, the use of UPS power supply as an emergency power supply, the operation is neither reliable, but also spend a lot of money, not sensible choice.
