Awareness of the necessity of power quality is increasing, and power factor correction (PFC) will be implemented on a growing scale in future. Enhancing power quality - improvement of power factor- saves cost and ensures a fast return on investment. In power distribution, in low - and medium - voltage network, PFC focuses on power flow (cos Ø) and optimization of voltage stability buy generating reactive power - to improve voltage quality and reliability at distribution level.
Benefits of power factor correction
- Amortization in 8 to 24 months through lower power costs: Power factor correction reduces the reactive power in a system. Power consumption and thus power cost drops in proportion.
- Effective installation use: An improved power factor means that an electrical installation works more economically (higher effective power for the same apparent power).
- Improved voltage quality
- Reduced voltage quality
- Optimum cable dimensioning: Cable cross-section can be reduced with improvement of power factor (less current). In existing installations for instance, extra or higher power can be transmitted.
- Reduced transmission losses: The transmission and switching device carry less current, i.e. only the effective power, meaning that the ohmic looses in the leads are reduced.
- Capacitor: Power factor correction capacitors produce the necessary leading reactive power to compensate the lagging reactive power. PFC capacitors should be capable of withstanding inrush currents caused by switching operations (> 100 * IR ) because the charging current comes from the grid as well as from capacitors parallel to the switched one.
- PFC Controller: Modern PFC controllers are microprocessorized. The Microprocessor analyzes the signal from a current transformer and produces switching commands to control the contractors that add or remove capacitor stages. Intelligent control by microprocessorized PFC controllers ensures an even utilization of capacitors steps, minimized numbers of switching operations and optimized life cycle of the capacitor bank.
- Capacitor Contractor: Contractors are electromechanical switching elements used to switch capacitors or reactors and capacitors in standards or detuned PFC systems. The switching operation can be performed by mechanical contacts or an electronic switch (semiconductor). The latter solution is preferable if fast switching is required for a sensitive load for example.
- Reactor (Compensation & Filtering): Power distributions networks are increasingly subjected to harmonic pollution from modern power electronic device, so called non-linear loads, e.g. drives, uninterruptible power supplies, electronic ballasts Harmonic are dangerous for capacitors connected in the PFC circuit, especially if the capacitors operate at resonant frequency. The series connection of reactor and capacitor to detune the series resonant frequency (the capacitors's resonant frequency) helps to prevent capacitor damage. Most critical frequencies are the 5th and 7th harmonics (250 and 350 Hz at 50 Hz). Detuned capacitors banks also help to reduce the harmonic distortion level and clean the network.
- Fuse: An HRC fuse or MCCB acts as a safety device for short circuit protection.
- HRC Fuses do not protect capacitors against overload - they are for short circuit protection.
- The HRC Fuse rating should be 1.6 to 1.8 time's nominal capacitor current.
- Don't use HRC Fuses for switching (risk of arcing!)