How to choose a right Mean well Switching Power Supply? A.To increase the reliability of the S.P.S., we suggest users choose a unit that has a rating of 30% more power than actual need.  For example, if the system needs a 100W source, we suggest that users choose a S.P.S. with 130W of output power or more. By doing this, you can effectively boost the reliability of the S.P.S. in your system B. Choosing functions based on your application: 1. Protection function: Over Voltage Protection (OVP), Over Temperature Protection (OVP), Over Load Protection (OLP), and etc. 2. Application function: Signaling Function (Power Good, Power Fail), Remote Control, Remote Sensing, and etc. 3. Special function: Power Factor Correction (PFC), Uninterruptible Power Supply (UPS) function.

C. Make sure that the model qualifies for the safety standards and EMC regulations you need. 1.Apparent Power=Input Voltage x Input Current (VA)  2.Real Power= Input Voltage x Input Current x Power Factor (W) 

From the environment friendly point, the electric power plant needs to generate a power which is higher than apparent power in order to steadily provide electricity to the market. The real usage of electricity should be defined by real power. Assuming the power factor is 0.5, the power plant needs to produce more than 2VA to satisfy 1W real power. On the contrary, if the power factor is 0.95, the power plant only needs to generate more than 1.06VA to provide 1W real power need. It will be more effective.