Load-50W-60W for AC-240V

Hi Friends,
Today let's discuss something interesting and different on the loads available for AC Voltage-240V.
If someone has to connect a load which could consume at least more than 5W at 32-40V AC & max 50-60W at 240V AC.
Operating hours are 18-24 Hours.
Wire wound solution is there but heat dissipation and life of resistors we should consider due to which no one can use this solution. So what should be the good and long time solution for it.
Let's discuss about it in detail.


Reagrds,
V.K. S.

Wire wound solution is there but heat dissipation and life of resistors we should consider due to which no one can use this solution.

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The question sounds confused.

Heat dissipation will occur with any load according to the accepted power. Wirewound resistors are hardly surpassable regarding lifetime and ruggedness.

How about using a 60 W light bulb?

vipinsaini said:

Wire wound solution is there but heat dissipation and life of resistors we should consider due to which no one can use this solution.

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If the load consumes 50-60W of power, then it will dissipate 50-60W of heat. There is nothing you can do about it.

If you use resistors with the correct power rating, they will last a long time. There is no problem.

vipinsaini said:

So what should be the good and long time solution for it.

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Wire-wound resistors.

FvM said:

The question sounds confused.

Heat dissipation will occur with any load according to the accepted power. Wirewound resistors are hardly surpassable regarding lifetime and ruggedness.

How about using a 60 W light bulb?

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"Wire wound solution is there but high temp. and life of resistors problem is there." Resistors becomes so hot which is not acceptable at all.
You are right that heat dissipation will occur. I wanted to use heat dissipation in other sentence but missed that sentence and by mistake used in wrong sentence.
Anyway, now i would like to bring the clarity that solution should be something in which temp. should be acceptable, should not very high.
Incandescent bulb & 12V MR16-Halogen bulb with electronic ballast-12V output is there but we have to avoid these lighting solutions as load.
So let's bring other solutions in which light products are not there.

Regards,
V.K.S.

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godfreyl said:

If the load consumes 50-60W of power, then it will dissipate 50-60W of heat. There is nothing you can do about it.

If you use resistors with the correct power rating, they will last a long time. There is no problem.


Wire-wound resistors.

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You are right that If the load consumes 50-60W of power, then it will dissipate 50-60W of heat. In my reply i already cleared that by mistake heat dissipation word used there.

10 wire-wound resistors were used with 100 Ohm,50W power in series but at 240V temp was so high which can't be acceptable.
So let's bring another solutions.

Regards,
V.K.S.

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godfreyl said:

If the load consumes 50-60W of power, then it will dissipate 50-60W of heat. There is nothing you can do about it.

If you use resistors with the correct power rating, they will last a long time. There is no problem.


Wire-wound resistors.

Click to expand...

You are right that If the load consumes 50-60W of power, then it will dissipate 50-60W of heat. In my reply i already cleared that by mistake heat dissipation word used there.

10 wire-wound resistors were used with 100 Ohm,50W power in series but at 240V temp was so high which can't be acceptable.
So let's bring another solutions.

Regards,
V.K.S.

If you want lower temperature, you need to use heatsinks to get rid of the heat.

What temperature is acceptable? Why is temperature a problem?

The amount of heat is the same which ever way you approach the problem. The only option is to force remove it. I would suggest using the resistors and add a cooling fan, either powered from somewhere else or used as part of the load. If you forced-air cool the resistors, 60W is no problem at all.

Brian.

godfreyl said:

If you want lower temperature, you need to use heatsinks to get rid of the heat.

What temperature is acceptable? Why is temperature a problem?

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Heatsink solution will be used but first trying to see how much lower temp. can be achieved without heat sink. Otherwise there is very good heat sink which has many fins so heat dissipation would be good.

Try to get temp. as low as possible. Due to application and place limitation temp. is the problem.

It's true that standard resistors are designed with relative high surface temperature at rated power. This implies usage of e.g. a protective grid or other kind of enclosure. If you want to reduce the surface temperature for some reason, you need to increase the surface. You can e.g. refer resistors designed for heatsink mount. Cooling fans are another means to reduce the surface temperature.

FvM said:

It's true that standard resistors are designed with relative high surface temperature at rated power. This implies usage of e.g. a protective grid or other kind of enclosure. If you want to reduce the surface temperature for some reason, you need to increase the surface. You can e.g. refer resistors designed for heatsink mount. Cooling fans are another means to reduce the surface temperature.

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If temp. is maintained with the help of heat sink then what about life of resistors. Vishay resistors are showing 1000 Hours life and application need at least 30,000 hours life.

Why do you want to waste the power of 60W, The world is growing......

Venkadesh_M said:

Why do you want to waste the power of 60W, The world is growing......

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Because there is need to consume 60W power that's why we want to do. It would be applied in parallel with a product because we overall system on which product is applied, coming under load condition. So to bring the overall system out from under load, we need to consume 60W load.

1000 h lifetime specification is related to 1% drift limit. You can expect much higher lifetime with some drift allowance. Running the resistor at reduced power (e.g. 50 %) will give effectively unlimited lifetime.

FvM said:

1000 h lifetime specification is related to 1% drift limit. You can expect much higher lifetime with some drift allowance. Running the resistor at reduced power (e.g. 50 %) will give effectively unlimited lifetime.

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Agreed with your suggestion of drift limit.
But you can see in the data that they mentioned + 25°C, 1.5 h “ON”, 0.5 h “OFF” too. And here load would is expected to run 24 Hours, temp. +25°C is also not possible to maintain. So if we run the load at 50% then on what basis we can say that it will give unlimited lifetime? Is there any formula or any something else which support it?

As you can derive from the derating curve, rated power is assuming an element overtemperature of 250 K. Halving the power reduces the element temperature by 125 K. If you apply typical lifetime versus temperature schemes (e.g. doubling with every 10 K reduction) you get effectively "unlimited" lifetime.