How do I start selecting a Panasonic relay?

First decide whether the relay switches a signal or a load. Then set the contact arrangement and the switching capacity from the circuit, choose the coil voltage from the control supply, and pick the terminal and sealing for the board. Those decisions narrow the range quickly.

Signal relay or power relay?

Choose a signal relay such as the TQ series to switch a low-level signal, where gold-clad contacts and a low thermal electromotive force keep the signal clean. Choose a power relay such as the JS or ACT series to switch a load, where the contacts must resist the inrush of a motor or a lamp. The duty, not the size, is the first decision.

How do I choose the coil voltage?

Match the coil to the available control supply and allow for the pick-up voltage, which is up to 75 percent of nominal. On a 5 V rail, a 4.5 V coil type gives more margin against a sagging supply than a 5 V type. Our FAE team can confirm the coil for your drive circuit.

What selection mistakes should I avoid?

The usual mistakes are ignoring the inrush of the load, choosing a coil that the drive cannot pull in reliably, and using a flux-resistant relay on a board that is washed. Each adds risk without benefit. Validate the choice on the bench before committing the BOM.

How do I size an electrolytic capacitor?

Match the voltage with margin, set the capacitance from the allowable ripple, then confirm the ripple-current rating at the hot case temperature. The ripple current and the temperature, not the capacitance alone, decide the life of the part. Our FAE team can run the ripple and lifetime estimate.

How much voltage margin should I leave?

Leave enough margin that the worst-case rail, including any transient or fault, stays below the rating. A 12 V rail with switching spikes should not use a 16 V part unless the spikes are controlled. When in doubt, step up to the next voltage class. Margin is cheap; a failed capacitor is not.

What is the endurance rating?

Endurance is the hours the capacitor survives at its maximum temperature with the rated ripple current. The FR series is rated 5000 to 10000 hours at 105 C, and the life roughly doubles for every ten degrees below that, so cooling the capacitor is the cheapest way to extend it. Request a lifetime estimate for your design.

Why does ripple current matter so much?

The ripple current multiplied by the impedance gives the internal loss that heats the capacitor, so a part that carries more ripple than it is rated for runs hot and fails early. A low-impedance part such as the FR series carries more ripple for the same case size. Check the ripple current at the switching frequency.

How do I rate a power relay for inrush?

A motor or a lamp draws a large inrush current for a short time, so the relay must be rated for that inrush as well as the steady current, or the contacts will weld or erode. Check the inrush figure in the datasheet, not just the resistive switching capacity. Our FAE team can check the inrush margin for your load.

Why do silver-tin-oxide contacts resist inrush?

Silver-tin-oxide is a contact material that resists welding and erosion under a high inrush current, which is the usual failure of a power relay in an appliance or a control panel. It is why the material, not just the current rating, matters for a motor or lamp load. Ask us about the contact material for your load.

How do I drive the coil?

Size the drive transistor for the coil current at the nominal voltage, and add a flyback diode across the coil to absorb the turn-off spike. Allow for the pick-up voltage, which is up to 75 percent of nominal, so the coil pulls in reliably even when the supply sags. Request a coil drive review.

Does the relay need to be sealed?

If the board is washed after soldering, use a sealed relay so the cleaning fluid does not contaminate the contacts. A flux-resistant relay is cheaper but cannot be washed. Confirm the protective construction code before you specify the part. Ask us for the sealed version of your rating.

What is the standout feature of the FR series?

It combines a low impedance, a high ripple-current capability and a 5000 to 10000 hour endurance at 105 degrees Celsius, so it lasts far longer than a standard capacitor in the same heat. That makes it the part for a compact or hot power supply. The value is the lifetime, not just the capacitance.

How do I estimate the life in my enclosure?

Measure or estimate the case temperature from the ambient, the ripple current and the thermal resistance, then apply the doubling rule: the life roughly doubles for every ten degrees below the maximum rated temperature. A capacitor that runs ten degrees cooler lasts about twice as long. Our FAE team can run the estimate for your design.

Why does the impedance matter?

The impedance sets how much ripple current the capacitor can carry and how much heat it generates, so a low-impedance part runs cooler and lasts longer in a high-frequency supply. The FR series is a low-impedance type for exactly that reason. Check the impedance at the switching frequency.

Can I get samples to evaluate?

Yes. We provide samples of the FR series for your own ripple and thermal testing, with documentation included and FAE support during evaluation. Request a sample and we will confirm stock and lead time.

Technical Support | Panasonic Expertise | BeiLuo

Guides, application notes and reviews from BeiLuo's FAE team covering Panasonic signal, power and automotive relays and aluminum electrolytic capacitors.

Guides 2 Application Notes 1 Troubleshooting 0 Reviews 1

How to Select a Panasonic Relay: A Practical Guide

2026-07-24 - Guides - By Li Wei

Compare Panasonic signal, power and automotive relays by contact arrangement, coil voltage and inrush rating to choose the right relay for your circuit.

Read guide

How to Select a Panasonic Electrolytic Capacitor

2026-07-17 - Guides - By Chen Yu

Voltage, capacitance, ripple current and lifetime guidance for choosing a Panasonic aluminum electrolytic capacitor for a power supply or a motor drive.

Read guide

Panasonic Power Relay Application Notes

2026-07-10 - Application Notes - By Li Wei

Contact material, inrush margin and coil drive guidance for Panasonic JS and ACT power relays in appliance, industrial and automotive load applications.

Read guide

No articles in this section yet. Contact our FAE team for assistance.

Panasonic Electrolytic Capacitor Lifetime Review

2026-07-03 - Reviews - By Zhao Hui

A hands-on review of Panasonic FR aluminum electrolytic capacitors, covering ripple current, thermal behaviour and how to estimate life in a real enclosure.

Read guide

Meet Our FAE Team

Li Wei

Senior FAE Engineer, Relays

RelaysContact RatingInrush

Author profile

Chen Yu

FAE Engineer, Capacitors

Electrolytic CapacitorRipple CurrentLifetime

Author profile

Zhao Hui

FAE Engineer, Applications

ReliabilityThermal DesignEMC

Author profile