Industrial Power Supplies Technical Questions

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  1. How do Mean Well test for Electro Magnetic Interference (EMI) ? This statement defines the EMI test setup and load style of MEAN WELL’s enclosed type and PCB type power supply referring to International EMI regulation CISPR 11 and CISPR 22. It also explains the way we make the CE declaration and emphasize that end users should re-check the EMI issue at ...
  2. Can MEAN WELL's power supply be used in the range of 45Hz ~ 440Hz? If YES, what will happen? MEAN WELL's power supply can be used within this frequency range. But if the frequency is too low, the efficiency will also be lower. For example, when a SP-200-24 is operated under 230VAC and rated load, if the frequency of AC input is 60 Hz, the efficiency is around 84%; however, if the ...
  3. When testing a dual output power supply, the +5V channel is correct, but the +12V channel is over the specification. What is going on? There are some minimum-load requirements on MEAN WELL's multi-output power supplies, please refer to the specification first before connecting the load. When the load condition is 5V/4A, 12V/0A, the output voltage of the 12V channel will be around 12.8V that is over the ?% of voltage deviation ...
  4. Why did the power supply shut down during operation and after turning it off, I can't restart the power supply again? In general there are two circumstances that will cause the power supply to shut down. The first one is the activation of the over-load-protection (OLP). To deal with this situation, we suggest increasing the rating of the output power or modifying the OLP point. The second one is the activation ...
  5. Why is the fan is not running after turning on certain models? Some models control the fan based on internal temperature to extend its life time. For example, the Fan ON temperature for the S-240 series is ≧ 40C (RT1). If the internal temperature does not reach the preset value, the fan will remain still until receiving the start up signal.
  6. What is "Inrush Current"? and What will we notice? On the input side, there will be (1/2 ~1 cycle, ex. 1/120 ~ 1/60 seconds for 60 Hz AC source) large pulse current (20~60A based on the design of S.P.S.) at the moment of power on and then back to normal rating. This "Inrush Current" will appear every time you turn on the power. Although it will ...
  7. What is PFC? PFC stands for Power Factor Correction. The purpose of PFC is to improve the ratio of apparent power and real power. The power factor is only 0.4~0.6 in non-PFC models. In PFC models, the power factor can reach above 0.95. The calculation formulas are as below: Apparent Power = Input ...
  8. What is the difference between -V and COM which are marked on the output side? COM (COMMON) means common ground. Please see below: Single output: Positive pole (+V), Negative pole (-V) Multiple output (Common ground): Positive pole (+V1, +V2,.), Negative pole (COM)
  9. In MEAN WELL's catalog, we see AC and DC at input, what does this mean? Due to different circuit designs, MEAN WELL power supply's input consists of three types as below:(√2VAC≒VDC)a.85~264VAC;120~370VDCb.176~264VAC;250~370VDCc.85~132VAC/176~264VAC by Switch; 250~370VDC In a and b inputs models, power supply can work properly no matter under AC or DC input. ...
  10. What is the fan control mechanism for SPS with cooling fan? Cooling fans have a relatively shorter lifetime (typical MTTF, Mean Time To Failure, of around 5000-10000 hours) as compared with other components of power supplies. As a result, changing operating method of cooling fans can extend the operation hours of the fans. The most common control methods ...

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