역률 보정 - PFC

Shop Arrow.com’s selection of power factor correction devices from industry-leading manufacturers. What is power factor correction? Power factor correction (PFC) devices are circuits or modules that improve power quality and efficiency by reducing the burden on the supply. Power factor is a characteristic of a power supply’s load defining the ratio of the real (active) power being delivered to the load to the apparent power being delivered. The apparent power is the absolute length of the vector sum of the real and reactive (stored) components of the power. It is caused by the voltage and current waveforms being out of phase because reactive components in the load require energy to maintain their electric field. A corrector changes the relationship between the AC voltage and current waveforms required by the load as seen by the source. This reduces the burden of the source. Active Power Factor Correction PFC is integrated with many switching controllers used for generating constant current or constant voltage supplies (for example fly-back controllers). They can typically employ a method called active PFC, in which they purposefully modulate the peak current limit on their input supply with a scaled version of the input voltage. Active PFC can provide power factors or 0.97 or higher. Dedicated PFC ICs can use other techniques to improve power factor, for example, continuous conduction boost mode and transition mode PFC devices. They are typically used in conditioning the power supply of applications like switch-mode power supplies, electronic ballasts and LED drivers. They facilitate devices meeting clean power requirements mandated by compliance regulations. Power Factor Correction Design Power factor correction design can have special considerations relating to their use with some devices. An example of this is incorporated the functionality in a motor driver with a variable speed drive switcher. Many applications have PFC capacitors in parallel with the motor to compensate for the inductive reactance of the motors windings and help improve its power factor on the supply line. Putting an additional PFC device in series can lead to high frequency switching occurring on the PFC power supply modules inverter exceeding the capacitors voltage rating. Serious noise issues can be caused if the PFC device is placed on the input or line side of a variable speed drive inverter. Inverters are extremely noisy and by in-lining the current and voltage and improving the power factor there can be an unfortunate effect of amplifying the amount of harmonic distortion to the current and voltage demands on the supply – lowering efficiency and increasing power supply noise. Many higher power applications have additional filtering requirements on their power supply inputs to reduce such noise effects. Soft starters may also have serious issues that need to be compensated for because of the high load required until a motor gets up to speed.