PFC

1. What is Power Factor?
  Power factor is the relationship between working (active) power and total power consumed (apparent power). Essentially, power factor is a measurement of how effectively electrical power is being used. A higher power factor represents a more effective use of electrical power.



2. Why improve low power factor?
  Low power factor means poor electrical efficiency. The lower the power factor, the higher the apparent power drawn from the distribution network. When low power factor is not corrected, the utility must provide the nonworking reactive power in addition to the working active power. This results in the use of larger generators, transformers, bus bars, wires, and other distribution system devices that otherwise would not be necessary.



3. What are harmonics?
  Harmonics are a form of noise, produced in frequencies which are a multiple of the basic 60 cycle sine wave. They are caused by switching power supplies and in other sophisticated machines, including computers and variable frequency drivers. Harmonics can distort the basic sine wave, as well as cause high currents on the neutral and ground wires in a system.



4. What are the benefits of Power Factor Correction?
  • Reduced electric utility bills ( a typical payback period is less than six months to a year)
  • Increased system capacity
  • Improved voltage
  • Reduced hear losses



5. What's difference between Active PFC and Passive PFC?
  Passive type use inductor, capacitor circuitry to reduce harmonic current, because power source frequency is 50Hz or 60Hz low frequency, it needs large inductor and capacitor. Moreover, the power factor improvement is not as good (about 0.75 ~ 0.8), limited improvement result, but the cost increased less.

Active type power factor correction using active component (control circuit and power sine conductor ON/OFF switch). Its fundamental working theory is to adjust input current waveform to looks like input voltage waveform, this can reach the point where power factor of 1 goal. Also, the input voltage range can be 90Vdc to 264V without additional switch for choosing the voltage range. To have a universal voltage model, this power factor regulator is a very important additional value. Otherwise, the cost increased more.



6. Which standards do Seasonic PFC products comply to?
  Seasonic's PFC products comply with CE standard: EN61000-3-2 + A1 + A2 (Limits for harmonica current emissions).



7. Why must you have PFC product?
  Recently, due to the popularity of electronic and computer product, as well as the increase awareness of environmental protection issue, therefore it has been listed as a improvement item. European CE mark has already require product with power consumption more than 300W (will be reduce in the future) to meet their harmonic current limit requirement. That means the power factor has to increase (about > 0.95) in order to meet CE requirement before a product can be market to Europe. Right now, countries other than one in Europe are planning to put these requirements into the law. Because of that, reducing power source harmonic current, increase power factor is a global environmental protection trend.



8. Why is Active PFC better than Passive PFC?

  Benefits of Active PFC:
  • Large buffer to EN harmonics requirement to ensure compliance.
  • Opportunity for future cost decreases as ICs requirement volumes increase.
  • Low risk in terms of material shortage.
  • A more "professional" solution than Passive.
  • Full range feature come with almost cost free.
  • Perfect power factor approach 1 for power utilization. (Environment friendly)
  • Better competition when power goes up was the trend of CPU's requirement.

  Negatives of Passive PFC:
  • Mass production of inductor must be accurate due to small buffer to EN harmonics limit.
  • Heavy weight that might create problems during transport. (Vibration & shock)
  • Possible shortage of ferrite material.
  • Vibration noise if structure is not fixed correctly.
  • Poor competition (cost and performance) when power up to 250W or more.



9. Why should you have Seasonic's Active PFC?
  Because Seasonic offers Active PFC power supplies for the price of Passive PFC units. Check it out today.