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A capacitor is a passive electrical component that stores and releases electrical energy in the form of an electric field. In industrial and commercial electrical systems, capacitors are primarily deployed for power factor correction (PFC), reactive power compensation, harmonic filtering, motor starting, voltage stabilisation, and energy storage in power electronics. By supplying the reactive (magnetising) current that inductive loads — motors, transformers, fluorescent lighting — would otherwise draw from the utility supply, capacitors reduce apparent power demand, lower energy bills, and relieve stress on cables, switchgear, and transformers.

Industrial power capacitors are rated in kVAr (kilovolt-ampere reactive) and manufactured to IEC 60831-1 & 2 (low-voltage shunt capacitors for AC systems) and, for Indian market products, to IS 13340. Key specifications include rated voltage (typically 415 V, 440 V, 480 V, or 525 V AC for Indian LV systems), rated reactive power in kVAr, frequency (50 Hz or 60 Hz), dielectric type (metalized polypropylene film — MPP), and temperature class (Class D: −25 °C to +55 °C being the most common for tropical climates).

At Electrihub we stock a comprehensive range of capacitors from the world's leading manufacturers — ABB, EPCOS-TDK, Schneider Electric, Siemens, and Lauritz Knudsen (formerly L&T Switchgear) — covering fixed power factor correction capacitors, heavy-duty and gas-filled cylindrical capacitors, rectangular box capacitors, and detuned filter capacitors for harmonic environments, for every industrial, commercial, and infrastructure application.

Types of Power Factor Correction Capacitors

Standard Duty (Normal Duty) MPP Capacitors

Standard duty capacitors use dry-type metalized polypropylene (MPP) film dielectric and are designed for clean sinusoidal networks with low harmonic content (THDU < 8%). They are suitable for fixed capacitor banks directly connected at the motor terminals or distribution boards in light industrial and commercial applications. Typical voltage ratings are 415 V, 440 V, and 525 V AC at 50 Hz, with reactive power outputs from 1 kVAr to 50 kVAr per unit. Standard duty units offer self-healing properties — a localised dielectric breakdown causes the metallised film to vaporise around the fault, isolating it and restoring capacitor function.

Heavy Duty (HD) MPP Capacitors

Heavy duty capacitors are specified for automatic capacitor banks where contactors switch the capacitor in and out of circuit repeatedly — typically 5,000 to 15,000 switching operations per year. They are constructed with heavier metallisation on the polypropylene film and incorporate reinforced internal connections to withstand inrush current transients. Heavy duty capacitors are also recommended for networks with moderate harmonic distortion (THDU up to 12%) and for applications involving frequent load variation, such as welding shops, press lines, and textile mills.

Gas-Filled (GH Duty) Capacitors

Gas-filled capacitors use an inert gas (typically nitrogen or mixed gas) as the impregnant instead of biodegradable resin, significantly enhancing thermal performance and operational lifetime — rated up to 220,000 hours or more under Class D conditions. They are specified for high-ambient-temperature environments (above 45 °C), tropical and coastal locations, and applications with very high switching frequency. The gas-filled construction also provides superior performance in harmonic-rich networks. Schneider Electric's VarplusCan GH series and EPCOS-TDK's PhaseCap HD gas series are widely used examples.

Detuned (Harmonic Filter) Capacitors

Detuned capacitors are used in conjunction with a series reactor to form a detuned filter circuit, preventing harmonic resonance in networks with significant non-linear loads (VFDs, UPS systems, rectifiers). The series reactor-capacitor combination is tuned to a frequency below the dominant harmonic order (usually the 5th, 250 Hz) by selecting a reactor with a relative impedance of 5.7%, 7%, or 14%. Detuned capacitors are rated for a higher voltage than standard units — typically 440 V or 525 V — to account for the voltage rise across the reactor. EPCOS-TDK's LT-APP series, Schneider Electric's VarplusCan APP series, and ABB's CLMD detuned variants are commonly specified for APFC panels in harmonic-rich environments.

Cylindrical (Round Can) Capacitors

Cylindrical capacitors are manufactured in a round aluminium or steel can housing. Their compact, space-efficient profile makes them well suited to modular automatic power factor correction (APFC) panels where multiple units are mounted side by side on dedicated rails or frames. EPCOS-TDK's PhaseCap, PhiCap, and Siemens' PhaseCap Energy+ series are the dominant cylindrical formats in Indian panel construction.

Rectangular Box (Square Can) Capacitors

Rectangular box capacitors offer higher kVAr ratings per unit in a compact footprint, and are well suited to large fixed banks and main bus compensation. ABB's CLMD series, Schneider Electric's VarplusBox series, and EPCOS-TDK's SquareCap (SqCap) series are widely used rectangular format capacitors in Indian MCC and main distribution panel installations.

Capacitor Brands and Series – Technical Comparison

The table below covers every capacitor brand and series stocked by Electrihub. Use the series name, dielectric type, duty class, voltage, and kVAr range columns to shortlist the right product, then follow the series link to browse available stock.

All capacitors are certified to IEC 60831-1 & 2. Indian manufactured products also comply with IS 13340. kVAr ratings shown are at 50 Hz. Refer to individual product datasheets for 60 Hz ratings, temperature derating curves, and complete voltage availability.

About the Capacitor Brands We Stock

ABB — CLMD Series Power Factor Correction Capacitors

ABB's CLMD series is one of the most widely specified low-voltage power factor correction capacitor ranges in the world, built using ABB's in-house manufactured metallized polypropylene film. The CLMD (Compact Low-loss Modular Dry) construction uses wound MPP elements encapsulated in thermosetting resin, enclosed in a steel box filled with inert vermiculite granules that safely absorb energy and extinguish any arc in the event of a fault at end of life. Each element is fitted with a sequential disconnector that individually isolates a failed element, allowing the capacitor to continue operating at reduced capacity rather than failing completely.

The CLMD range covers voltage ratings from 220 V to 1,000 V AC and kVAr outputs from 3.3 kVAr (CLMD 13) up to 120 kVAr (CLMD 83). CLMD 13 is optimised for modular capacitor bank assembly with parallel-connection capability. CLMD 33/33S offers a compact high-power-density design for capacitor banks. CLMD 43 to 83 are the standard workhorse series for general power factor correction in industrial distribution and motor control centres. Built-in discharge resistors on CLMD 43–83 reduce voltage to below 50 V within one minute of disconnection, meeting IEC 60831 safety requirements. Dielectric losses are below 0.2 W/kVAr — among the lowest in the industry.

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EPCOS-TDK — PhaseCap, PhiCap, SquareCap, LT-APP Series

EPCOS, now a TDK product brand (TDK Electronics), is India's largest manufacturer of power factor correction capacitors by installed base. EPCOS India Pvt. Ltd. (EIPL) manufactures and markets the full range locally, making EPCOS-TDK capacitors among the most readily available and cost-competitive high-quality PFC capacitors in the Indian market. All EPCOS-TDK capacitors conform to IEC 60831-1 & 2 and IS 13340, and carry ISI marking for Indian tender requirements.

The PhaseCap series (B25655, B32344) is the flagship cylindrical normal-duty capacitor for APFC panels, available in 415 V, 440 V, and 525 V with self-healing dry MPP (biodegradable soft resin) construction and an over-pressure safety interrupter. The PhaseCap HD series is the heavy-duty gas-filled version rated for up to 15,000 switching operations per year and operating lifetimes exceeding 220,000 hours, suitable for high-temperature and high-cycle environments. The PhiCap series (B32344) is the everyday normal-duty cylindrical capacitor for standard fixed and automatic PFC applications at 440 V and 525 V. The SquareCap (SqCap) series provides a rectangular box format for higher kVAr ratings in fixed bank applications. The LT-APP series is the detuned application capacitor designed for use with series detuning reactors in harmonic-rich networks, rated at higher voltage to accommodate the reactor voltage rise.

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Schneider Electric — VarplusCan, VarplusBox, EasyLogic PFC Series

Schneider Electric's Varplus range provides a complete portfolio of LV power factor correction capacitors for every application from light commercial to heavy industrial. All Varplus capacitors use metallized polypropylene film with a Zn/Al alloy metallisation and wave-cut film edges that enhance self-healing performance and reduce partial discharge. They are available in normal, heavy, and gas-heavy duty grades, and in both standard PFC and detuned (APP) harmonic filter versions.

The VarplusCan ND (Normal Duty) is the standard cylindrical capacitor for fixed and automatic PFC banks at 415–525 V. The VarplusCan HD (Heavy Duty) is rated for high-frequency switching duty in automatic banks. The VarplusCan GH (Gas Heavy Duty) uses gas-filled construction for superior performance in high-ambient-temperature conditions above 45 °C and tropical coastal environments — widely specified in Indian infrastructure and industrial projects. The VarplusCan APP (Detuned) is for use with series detuning reactors in harmonic-polluted networks at 440 V and 525 V. The VarplusBox series is the rectangular high-power option for main bus compensation and large fixed banks up to 100 kVAr per unit. The EasyLogic PFC / EasyLogic PFC+ series is Schneider's value-priced cylindrical range for small and medium APFC panels in commercial and light-industrial applications.

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Siemens — PhaseCap Energy+ 4RB Series

Siemens markets its LV power factor correction capacitors under the PhaseCap Energy+ brand name, with the product range built on the same EPCOS-TDK film capacitor technology platform. The PhaseCap Energy+ family is available in three sub-series differentiated by duty class and construction. The 4RB2 is the standard duty resin-filled cylindrical unit for clean networks and fixed compensation, covering 0.4–30 kVAr (3-phase) at 400–440 V. The 4RB7 is the heavy-duty resin version rated for automatic switching with up to 5,000 switching operations per year and overcurrent tolerance up to 1.3× rated current, covering 0.5–33.7 kVAr (3-phase). The 4RB8 is the premium gas-filled variant with an expected lifetime of 220,000 hours (gas) or 240,000 hours (resin) and overcurrent tolerance up to 2.0× rated current — rated for up to 15,000 switching operations per year, making it the ideal choice for rapid-cycling APFC panels and high-harmonic environments up to 56 kVAr (3-phase) at 400–525 V.

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Lauritz Knudsen (formerly L&T Switchgear) — LTCCA, LTBCA Series

Lauritz Knudsen Electrical & Automation (formerly L&T Switchgear) manufactures ISI-marked power factor correction capacitors to IS 13340 and IEC 60831-1 & 2, designed specifically for Indian network conditions. All Lauritz Knudsen capacitors use superior-grade metalized polypropylene (MPP) film with ingress-free metal construction for natural ambient cooling, high-viscosity leak-proof resin as impregnant, and a built-in over-pressure safety interrupter.

The LTCCA series is the standard cylindrical (round can) capacitor for automatic PFC panel applications at 415 V, 440 V, and 525 V, available in normal and heavy-duty versions from 1 kVAr to 50 kVAr. The LTBCA (Box Cap / Agri Cap) series is a rectangular box capacitor widely used for agricultural pump motor compensation and fixed PFC at distribution feeders, available at 415 V and 440 V from 1 kVAr to 25 kVAr. The LTCCA-HD heavy-duty series is specified for high-cycle automatic APFC panels. ISI marked and BIS compliant, Lauritz Knudsen capacitors are widely specified in government infrastructure tenders, state electricity board feeder compensation schemes, agricultural sector installations, and large industrial APFC panels across India where IS-certified products are a mandatory requirement.

Browse All Lauritz Knudsen Capacitors →

Where Are Power Capacitors Used?

Automatic Power Factor Correction (APFC) Panels — The most common application. Multiple capacitor steps are switched in and out of service by a power factor controller (PFC relay) in response to the load's reactive demand, maintaining the system power factor at or above a target set-point (typically 0.95–0.99 lagging). Each step uses one or more capacitor units switched by a dedicated capacitor duty contactor.

Fixed Power Factor Correction at Motor Terminals — A fixed capacitor bank connected directly to the terminals of an induction motor provides reactive compensation locally at the source, reducing reactive current on the entire cable run from the MCC to the motor. This is particularly effective for large, continuously running motors in pumping stations, compressor rooms, and HVAC plants.

Main LT Bus Compensation — Large rectangular box capacitors (ABB CLMD 63/83, Schneider VarplusBox, EPCOS SqCap) are connected at the main LT bus of a transformer or at the main distribution board to provide bulk reactive power compensation and improve the transformer's power factor — reducing the kVA demand billed by the utility and relieving the transformer of unnecessary reactive loading.

Detuned Filter Banks in Harmonic-Rich Environments — In plants with significant non-linear loads (variable frequency drives, UPS systems, rectifiers, induction furnaces), plain capacitors are at risk of harmonic resonance and overloading. Detuned filter capacitors (EPCOS LT-APP, Schneider APP, ABB CLMD detuned) combined with a series reactor eliminate this risk, allowing safe power factor correction in harmonic-polluted networks.

Agricultural Feeder Compensation — Distribution utilities and state electricity boards (SEBs) install capacitor banks at feeder distribution points and agricultural pump transformers to compensate for the low power factor of agricultural motor loads. Lauritz Knudsen LTBCA box capacitors and EPCOS PhiCap units are widely used in this sector.

Reactive Power Compensation in Infrastructure Projects — Metro rail, airports, data centres, large commercial complexes, and water treatment plants specify APFC panels with heavy-duty or gas-filled capacitors to maintain high power factors under varying load conditions, avoid utility reactive energy penalties, and reduce carbon footprint.

How to Select the Right Capacitor

Step 1 — Calculate the required reactive power (kVAr)

The kVAr required for power factor correction is calculated from the active load (kW), the existing power factor (cos φ₁), and the target power factor (cos φ₂): kVAr = kW × (tan φ₁ – tan φ₂). For automatic panels, total kVAr is divided into steps (typically 4–16 steps) controlled by the APFC relay. For fixed compensation at motor terminals, the correction kVAr is selected to just compensate the motor's no-load reactive demand.

Step 2 — Select the correct rated voltage

Select the rated voltage to match your supply system: 415 V for standard Indian LV systems, 440 V for systems with regular voltage swells, 480 V for 480 V industrial systems, and 525 V for detuned filter applications where the series reactor raises the capacitor terminal voltage. Always select a capacitor rated at or above the maximum continuous voltage at the point of connection — never operate a capacitor rated at 415 V on a 440 V network.

Step 3 — Choose the right duty class

For fixed compensation (rarely switched): Normal Duty (ND) is sufficient. For automatic panels switched by contactors at rates of up to 5,000 times per year: use Heavy Duty (HD). For high-cycle applications (5,000–15,000 switchings/year), high ambient temperatures above 45 °C, or tropical/coastal locations: select Gas-Filled (GH) heavy duty capacitors. For networks with VFDs, UPS, or other non-linear loads creating significant harmonics: select Detuned (APP) capacitors with a series reactor.

Step 4 — Assess the harmonic environment

If total harmonic voltage distortion (THDU) at the point of connection exceeds 8%, plain capacitors risk resonance amplification and premature failure. Measure or calculate the THDU and select detuned filter capacitors with an appropriate series reactor (5.7%, 7%, or 14% impedance) for safe operation in harmonic-rich networks.

Step 5 — Verify ambient temperature and enclosure requirements

Standard capacitors are rated to Class D (+55 °C maximum ambient). In environments where panel internal temperatures regularly exceed 45 °C — common in Indian industrial plants during summer — derate the kVAr rating or select gas-filled heavy-duty capacitors rated for higher thermal performance. Ensure the panel enclosure has adequate ventilation or forced cooling to maintain capacitor temperatures within the rated range.

Key Technical Terms — Power Capacitors

Power Factor (cos φ)

The ratio of active power (kW) to apparent power (kVA) drawn from the supply. A power factor of 1.0 means all current drawn from the supply does useful work. Inductive loads (motors, transformers) have a lagging power factor below 1.0. Utilities in India penalise consumers for power factors below 0.9 and typically bill reactive energy (kVArh) consumption above a threshold. Power factor correction capacitors supply reactive current locally, reducing reactive current drawn from the supply and improving the system power factor.

kVAr (Kilovolt-Ampere Reactive)

The unit of reactive power. The rated kVAr of a capacitor specifies the reactive power it can supply to the network at its rated voltage and frequency. If a capacitor rated at 10 kVAr / 415 V is operated at a higher voltage, its actual kVAr output increases as the square of the voltage ratio — a 415 V unit on a 440 V system delivers approximately 10 × (440/415)² ≈ 11.2 kVAr.

Self-Healing Dielectric

Metalized polypropylene (MPP) capacitors are self-healing. When a localised dielectric breakdown occurs, the electrical energy at the fault vaporises the thin metal film immediately around the fault point, isolating it electrically and restoring the capacitor's insulation. This allows the capacitor to survive localised dielectric faults and continue operating, giving MPP capacitors a significantly longer service life than older paper-film-oil (PFO) designs.

Harmonic Resonance

When a capacitor bank is connected to an inductive supply impedance (transformer leakage reactance + cable impedance), the LC combination resonates at a natural frequency. If this resonant frequency coincides with a significant harmonic component in the network (e.g., the 5th harmonic at 250 Hz), harmonic currents are amplified, causing capacitor overloading, overheating, and premature failure. Detuned filter reactors shift the resonant frequency below the lowest significant harmonic, eliminating this risk.

APFC (Automatic Power Factor Correction)

An APFC system automatically switches capacitor banks in and out of service in response to the load's reactive demand, using a power factor controller (PFC relay) that measures the system power factor and issues switching commands to capacitor duty contactors. APFC panels maintain the system power factor within a tight band around a target set-point regardless of load variation — essential for facilities with widely fluctuating reactive loads.

Detuning Reactor

A detuning reactor is a series inductor connected in series with a capacitor to form a detuned LC filter. The reactor's impedance is expressed as a percentage of the capacitor's impedance at rated frequency. A 7% reactor tunes the LC circuit to approximately 189 Hz — well below the 5th harmonic (250 Hz) — preventing resonance at that harmonic order. The reactor also limits inrush current when the capacitor is switched, reducing contactor wear.

Frequently Asked Questions — Capacitors

What is the difference between a normal duty and heavy duty capacitor?
Normal duty (ND) capacitors are designed for fixed compensation or APFC panels with low switching frequency (up to 1,000 switchings per year). Heavy duty (HD) capacitors use heavier metallisation on the polypropylene film, reinforced internal connections, and sometimes gas-filled construction to handle the thermal and electrical stress of frequent contactor switching — up to 5,000 or 15,000 operations per year for HD and gas-HD units respectively. For any APFC panel application, always specify Heavy Duty or above.

Can I use a 415 V capacitor on a 440 V supply?
Technically, the capacitor will operate, but it will be continuously over-rated. A 415 V capacitor operating on a 440 V supply experiences 6% voltage overstress permanently, which reduces its service life significantly. For 440 V systems, always select capacitors rated at 440 V or 480 V. Also note that the kVAr output increases as the square of the voltage, so correct sizing requires using the actual supply voltage in the kVAr calculation.

How many kVAr do I need to correct my power factor from 0.80 to 0.95?
Use the formula: kVAr = kW × (tan φ₁ – tan φ₂). For a 100 kW load at 0.80 power factor corrected to 0.95: tan(cos⁻¹(0.80)) = 0.75; tan(cos⁻¹(0.95)) = 0.329. kVAr required = 100 × (0.75 – 0.329) = 42.1 kVAr. Contact our technical team or use our capacitor sizing guide for assistance.

Do I need detuned capacitors if I have VFDs in my plant?
Yes, in most cases. Variable frequency drives (VFDs), soft starters with diode rectifiers, UPS systems, and other non-linear loads inject harmonic currents into the network. These harmonics can cause resonance between the supply impedance and a plain capacitor bank, resulting in overloading, overheating, and failure of the capacitors. If THDU at the capacitor connection point exceeds 8%, select detuned filter capacitors (EPCOS LT-APP, Schneider APP, or equivalent) with a matching series detuning reactor.

What is the recommended minimum time before re-energising a capacitor after switching off?
Capacitors must be fully discharged before re-energisation to prevent switching transients from adding to residual charge, creating damaging voltage spikes. IEC 60831 requires capacitors to discharge to below 75 V within 3 minutes (for units with built-in discharge resistors). Most manufacturers recommend a minimum wait of 40–60 seconds between disconnection and re-energisation. APFC relay settings should incorporate a minimum off-time delay (anti-oscillation timer) of at least 40 seconds per step.

What is the difference between a cylindrical (can) and a rectangular box capacitor?
Cylindrical capacitors are compact, easy to mount in modular APFC panel rail assemblies, and available in lower kVAr ratings (typically up to 50 kVAr per unit). Rectangular box capacitors offer higher kVAr per unit in a space-efficient format, are better suited to large fixed banks and main bus compensation, and are easier to connect with high cross-section cables on large threaded terminals. ABB CLMD, Schneider VarplusBox, and EPCOS SqCap are rectangular box formats; all other Varplus, PhaseCap, and LK series are cylindrical.

Are Electrihub's capacitors original and genuine?
Yes. Electrihub sources all capacitors exclusively through authorised distribution channels directly from manufacturers. All products are supplied in original manufacturer packaging with full traceability. Manufacturer certificates of conformity and test certificates are available on request for project and tender requirements.

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