Capacitors & Power Factor Correction
Inductive loads like motors, drives, and transformers draw reactive power from your electrical system, increasing total current draw and potentially triggering utility power factor penalties. Power factor correction capacitors offset that reactive power locally, reducing current draw and freeing up system capacity. Depending on your system, that might mean individual units at a specific load, or grouped units automatically switching banks across a distribution system. The right configuration depends on how much reactive power needs correction and how your system is arranged. Wistex supplies power factor correction capacitors and capacitor banks for industrial applications, sized to your voltage, phase, kVAR rating, termination style, and enclosure requirements.
What to Consider When Selecting Power Factor Correction Capacitors
Start with the electrical characteristics of the system you’re correcting. Voltage and phase need to match the application, and the kVAR rating must align with the reactive power you need to compensate for. Size against actual load conditions rather than nameplate assumptions; sizing too aggressively or too lightly reduces effectiveness. Installation matters just as much. Termination style, mounting method, fusible protection, and NEMA enclosure rating all affect whether the capacitor suits your environment, especially in dusty, moist, or harsh conditions.
Correction Methods
Individual Fixed Correction
Capacitors are installed directly at individual pieces of equipment, such as large motors, and switch on and off with that equipment. This corrects power factor at the point where the reactive load is created.Group Correction
A bank of capacitors is connected to a distribution board serving several smaller motors or loads. This suits installations where individual correction at each load would be impractical or uneconomic.
Automatic Switched Capacitor Banks
Installed at the main switchboard, these systems use a controller to monitor facility power factor and automatically connect or disconnect capacitor steps as load changes through the day. This suits plants where load varies significantly across a shift.
Capacitors and Harmonic Distortion
Facilities with a high percentage of non-linear loads, such as variable frequency drives (VFDs) or LED drivers, can run into trouble with standard power factor correction capacitors, which may resonate with system harmonics and fail prematurely. In these environments, detuned capacitor banks pair the capacitor with a reactor tuned below the dominant harmonic frequency to prevent resonance while still delivering reactive power compensation. Wistex supplies capacitors, line reactors, and harmonic filters, and can help you match the right combination to your harmonic environment if your facility runs significant VFD load. Complete your power quality setup with line reactors and harmonic filters for detuned and harmonic-sensitive applications.
Frequently Asked Questions
A power factor correction capacitor supplies leading reactive power to offset the lagging reactive power drawn by inductive loads such as motors and transformers. This aligns the current and voltage waveforms more closely, reduces total current drawn from the supply, and improves the efficiency of the electrical system.
Start by matching the capacitor to the system voltage, phase, and required kVAR rating. Then determine whether correction should be applied at an individual load or across a distribution system, and confirm the mounting method, termination style, and enclosure rating suit the installation environment.
An individual capacitor bank is used when power factor correction is needed close to a specific load, such as a large motor. This corrects the power factor at the source of the reactive demand rather than across a broader section of the electrical system.
Standard capacitors can resonate with the harmonics that VFDs produce and may fail as a result. Facilities with significant VFD load require detuned capacitor banks, which pair the capacitor with a reactor to prevent resonance while still correcting power factor.