How do I start selecting a Faratronic capacitor?

First decide the function: DC link, snubber or motor run. Then fix the voltage class from the circuit, set the capacitance from the application, and choose the case style from the space and the environment. Those three decisions narrow the range quickly.

DC-Link, snubber or motor capacitor: how do I choose?

Choose a DC-Link capacitor to hold the bus voltage and carry ripple current, a snubber capacitor to clamp the turn-off spike across a switch, and a motor run capacitor to set the phase shift in a single-phase motor. The function, not the value, is the first decision.

How do I check the ripple current?

Estimate the RMS current at the switching frequency, then compare it with the capacitor rating at the hot case temperature. If the margin is small, choose a lower-ESR part or more capacitance rather than relying on a nominal figure. Our FAE team can run the ripple estimate for you.

What selection mistakes should I avoid?

The usual mistakes are ignoring the ripple current, choosing a voltage class from the nominal bus without overshoot margin, and sizing a motor capacitor by the nearest value rather than the motor requirement. Each adds risk without benefit. Validate the choice on the bench before committing the BOM.

How do I size the DC-Link capacitance?

Start from the allowable bus-voltage ripple at the switching frequency, then confirm the capacitor can carry the resulting RMS ripple current at the hot case temperature. Energy storage for a load step is a secondary check. Ripple current, not capacitance, usually sets the final choice.

Why is ESR important in a DC-Link capacitor?

The equivalent series resistance converts a fraction of the ripple current into heat inside the capacitor, so a lower ESR means a cooler part and a higher usable ripple current. That is the main reason a film capacitor outlives an electrolytic of the same value. Check the ESR at the hot case temperature.

How should I place the DC-Link capacitor?

Place it as close to the switch module as the layout allows, and connect it with the shortest, widest conductors, so the loop that carries the switching current has the smallest area. A large capacitor on long leads has more inductance than a small one placed correctly. Placement matters as much as value at high frequency.

Can a film capacitor replace an electrolytic bank?

Yes, and it usually improves reliability. Match the total capacitance and the ripple-current rating of the bank, then choose a case that fits the space. The film part removes the dry-out failure mode and the end-of-life capacitance loss. Our FAE team can compare the two options.

How do I size a snubber capacitor?

Estimate the energy stored in the commutation-loop inductance at turn-off, then choose a capacitance that clamps the resulting spike within a safe margin below the module rating. The voltage class should exceed the worst-case clamp level with margin. Too much capacitance adds loss; too little fails to clamp.

Why does loop inductance matter so much?

The overshoot is the loop inductance multiplied by the rate of change of current, so the best snubber in a bad layout still fails. Keep the snubber loop and the commutation loop as small as possible, and mount the capacitor at the module terminals. Layout dominates snubber performance.

Does a snubber reduce EMI?

Yes. The ringing that a snubber damps is a source of radiated and conducted EMI, so clamping the spike also lowers the high-frequency noise. That can reduce the effort needed elsewhere in the filter and shielding. Measure the waveform at the module, not the bus.

PCB or lug-terminal snubber?

Use a PCB snubber when the capacitor mounts on the driver or power board close to the module. Use a lug-terminal snubber when the capacitor bolts directly across the module busbars in a power stack, because that gives the shortest and lowest-inductance loop. Choose the option that shortens the loop.

What makes Faratronic motor capacitors stand out?

They combine stable capacitance, self-healing metallized polypropylene film and, in the C65 and C6G, a safety-focused case design. The C6G reaches the S3(P2) safety class and the C65 adds an explosion-proof case for compressors. The value is in the lifetime, not just the initial capacitance.

How does capacitance drift affect a motor?

A motor run capacitor that loses capacitance over time reduces the phase shift, which lowers starting torque and raises running current and winding temperature. A stable film capacitor keeps the motor operating near its design point for its whole life. Match the tolerance to the motor requirement.

What does the explosion-proof case protect?

The pressure-disconnect mechanism opens the circuit if the internal pressure rises at end of life, so the capacitor fails safe rather than venting or bursting. That protects the equipment around it, which is why the style is used in refrigeration and air conditioning. It is a safety feature, not just a case style.

Can I get samples to evaluate?

Yes. We provide samples of the C61 and C65 capacitors for your own lifetime and temperature testing, with documentation included and FAE support during evaluation. Request a sample and we will confirm stock and lead time.

Technical Support | Faratronic Expertise | BeiLuo

Guides, application notes, reviews and troubleshooting from BeiLuo's in-house FAE team covering Faratronic DC-Link, snubber and AC motor film capacitors.

Guides 1 Application Notes 2 Troubleshooting 0 Reviews 1

How to Select a Faratronic Film Capacitor: A Practical Guide

2026-07-24 - Guides - By Xu Ming

Compare Faratronic DC-Link, snubber and AC motor film capacitors by capacitance, voltage class and ripple current to choose the right part for your design.

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Faratronic DC-Link Capacitor Application Notes

2026-07-17 - Application Notes - By Xu Ming

Capacitance, ripple-current and thermal design guidance for Faratronic DC-Link film capacitors in inverters, photovoltaic converters and power supplies.

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Faratronic IGBT Snubber Capacitor Application Notes

2026-07-10 - Application Notes - By Gao Peng

Snubber capacitance, voltage class and loop layout guidance for Faratronic snubber capacitors that protect IGBT modules from turn-off overvoltage and ringing.

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Faratronic AC Motor Capacitor Review: C61 and C65 Series

2026-06-30 - Reviews - By Zhou Lan

A hands-on review of Faratronic AC motor run capacitors, covering the C61 box and C65 explosion-proof cylinder, capacitance stability, safety class and lifetime.

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Meet Our FAE Team

Xu Ming

Senior FAE Engineer, Film Capacitors

Film CapacitorDC-LinkThermal Design

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Zhou Lan

FAE Engineer, Motor Capacitors

AC Motor CapacitorSelf-healingSafety Class

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Gao Peng

FAE Engineer, Snubber and High Voltage

SnubberIGBTEMC

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