Power Loss In A Relay

It is even not clear which losses the client meant - the ones lost by load in the contacts (probbaly, mostly heat), or the ones lost by the relay construction (heat, stray currents, sound). The both are negligeable - only worth consideration if there were thousands of the relays, and anyway, little can be done here.

Your wrong but the answers in the information you gave.

Think about what's using power in the relay

so you are saying the consumption of the relay coil is the power loss?

Well, what other ones are there?

The ralay does the useful work of the connection of the load to the supply. The losses in it is just a fraction of the power consumed by it.

I overlooked the "rated thermal current" in the OP. At less load the 6A rated thermal elements will produce less heat, at more load, more heat. So in them losses will depend on load (in the coil do not depend).

It is not desirable to operate the relay at any current higher than what the manufacturer specifies. The thermal current is usually the highest of the rated values, the rated operational current under different duties are less. The user must never exceed these ratings when using the relay. So, the question of higher currents should not arise in usage.

What thermal elements?

It's a NO / NC relay, not an O/L or MCB. The only heat from the current will be via the volt drop across the contacts and other internal bits.

Quite right you are Tony. But in the bigger picture of energy conservation, it is the duty of designers to keep the perpetual loss low. Every bit counts.

Here is what ABB declares for their 6A control relay...

Negligible maybe, still, shows that they are trying....

In these days of energy conservation initiatives, it is quite normal for customers to ask, and manufacturers to provide power-loss-per-pole figures for most equipment. Here is one example of an electronic relay from ABB

KVS - Interesting! I have "learnt" something today.

Thank you, you made my day

However, this table refers to an electronic motor-protection relay. The OP really was referring to a "control relay", a 2NO+2NC small contactor ... the wattage wasted there in the current path is naturally much lower, please see post # 10.

Thanks kvsridhar for this excellent information in regard to power consumption of the relay. In fact, in today's world, everyone is trying to save energy whether small or large quantum; for example,like relays ,engineers prefer low power consumption HRC fuses,choice of LED indication lamps instead of filament indication lamps etc. in panel building works.

As was said in the beginning, you must first determine the intent of the question.

If all they want to know is the power losses as a result of the coil being energized, most relay mfrs will state that in their data sheets, usually referred to as the "Sealed" VA or W consumption. Basically because of the nature of a relay, all of the sealed power is going to be rejected as heat, so you could say it is 100% losses.

If they want to know the total aggregate power loss, as in watts for determining heat rejection, then you would add the relay power consumption and the resistance losses of the contacts.

If they want to know the losses inserted into the circuit flowing THROUGH the relay contacts, sometimes called "insertion losses", for the purposes of determining true power consumption at a load down stream, that's a different matter and a little more complex.