What is the difference between a high frequency UPS and a Low frequency UPS? Which one is better?

Brief answer:

The HF UPS converts the battery DC to a high voltage CD, using a high frequency switch-mode converter. The HVDC goes through an array of FET transistors, which are driven to generate an approximation of AC mains. Cheaper ones make a stepped square wave, better ones a near sine wave. That HV converter is relatively lightweight. Most of the mass of such an inverter is the battery. For the low frequency type, the DC goes into an iron power transformer (which is usually dual function as the battery charger transformer), and driven on the low voltage side to simulate AC, which directly comes out the 120V side of the transformer. The Iron transformer is usually pretty large, and a good part of the mass of the inverter, along with the battery.

More answer:

When users purchase equipment should be based on their actual needs, rather than blindly follow. For example, users want to build in large data centers, then the reliability and stability of the requirements should be the first place, high frequency UPS should be the first choice; if it is a general office applications, or major Taking into account the space occupied by the device, you can use high frequency UPS.

(1) in terms of reliability, Low Frequency Ups confidential superior High Frequency Ups machine frequency converter machine using thyristor (SCR) rectifiers, after half a century of development of the technology and innovation, has been very mature, and its current impact resistance ability is very strong. Because SCR semi-controlled devices, does not appear straight, false triggering other faults. In contrast, high-frequency machine uses high frequency IGBT rectifier Although higher switching frequency, but there are strict voltage, current work area when the IGBT operation, low impact resistance. Thus the overall reliability, IGBT rectifier lower than SCR rectifier.

(2) in terms of environmental adaptability, High Frequency Ups confidential superior frequency machine High Frequency Ups is a microprocessor as the process control center, the complex hardware analog circuit programming in the microprocessor, by way of a software program to control the operation of the UPS. Therefore, size, weight, and other aspects significantly reduced, noise is also small, space, the environment is small, and therefore more suitable for less demanding on the reliability of office space. Because of this, many manufacturers of small power UPS generally launched high-frequency machine. 

(3) zero voltage at the load on the requirements, the frequency confidential superior high frequency three phase ups machine zero line will be introduced as a neutral point of positive and negative rectifier and bus, this structure would inevitably result in the rectifier and inverter harmonic coupling the zero line, uplifting zero voltage, resulting in zero voltage raise the load side, it is difficult to meet IBM, HP and other server manufacturers of the zero voltage is less than 1V venue needs. In addition, when the mains and generator switching frequency machine is often due to the zero line is missing and must transfer bypass operation, the load may cause major flash failure in certain conditions. Frequency machine because the rectifier is not required to participate in the work of the zero line, while at the zero line disconnection, UPS can maintain normal power supply.

Therefore, the difference-frequency and high frequency UPS mainly on the isolation transformer, and the use of an isolation transformer frequency machine, in large part to enhance the reliability of the UPS. In terms of the overall performance, and high frequency machine machines are advantages and disadvantages, at least in the present, there is no question of who replaced who.