A Capacitor for Harmonic Filter is a specialized electrical component used to reduce or eliminate harmonic distortion in power systems. Harmonics are unwanted frequencies—typically multiples of the fundamental frequency—that can distort the electrical waveform, reduce efficiency, and damage equipment. These are often caused by non-linear loads such as inverters, rectifiers, or other power electronics.

Purpose and Function:

• It works as part of a harmonic filter network, which typically includes capacitors, inductors (reactors), and sometimes resistors.
• The capacitor provides reactive power compensation and helps maintain power factor.
• When combined with reactors, it forms a tuned filter that targets specific harmonic frequencies and suppresses them from the system.

Application in Railways:

In railway systems, where heavy-duty electrical equipment like traction motors and converters operate, harmonic filters help ensure:

• Stability of power supply
• Protection of sensitive signaling and control systems
• Compliance with electrical standards (like CLW specifications in India)

So, a Capacitor for Harmonic Filter (e.g., 66.6 µF, 2500V AC as per CLW/ES/3/0087/C) is essential for maintaining clean power quality, particularly in complex, high-load environments like railways.