Mechanical relay: higher current than rated current at lower voltage than switching voltage

Question

In general, is it advisable/safe to switch a mechanical relay with the following abstract conditions?

• load voltage << rated switching voltage
• load current > rated current

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Relevant Questions

• Relay: higher voltage allowed at lower current? states the following

The current rating is to limit the self-heating of the relay due to its own resistance.

• Understand Relay Specifications to Get the Most Out of Your Switching System

maximum current that the relay can sustain when being opened or closed and not sustain contact damage

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My Use Case

I have a mechanical relay (Digi-Key PN 281-6348-ND) with the following specs:

• Switching Voltage: 250 Vac
• Contact Current Rating: 10 A

I would like to use it to PWM control a 12 Vdc thermoelectric plate (Peltier module) rated to pull up to 15 A.

Answer 1

The current rating determines the \$I^2R\$ losses of the closed contact hence, operating at 15 amps when the rating is 10 amps is going to result in early failure of the relay. The voltage rating determines characteristics of the contact when it opens. There is usually no trade off.

Answer 2

Some switches and relays are rated for higher current at lower voltage, however this relay is specifically limited to 10A in the datasheet, even at 24V.

If you exceed the maximum rating, especially by a factor as large as 50%, you can expect unpleasant things to happen.

Answer 3

Your correct course is to use a larger relay with a higher current rating. Simple as that.

The issue is thermal, and is caused by current. The voltage doesn't really enter into it. So using a lower than intended voltage doesn't help.

Voltage matters to the relay's ability to interrupt an arc. At your low voltage, that's not the question; it's the contact heat when active.