# Help me. can somebody tell me an info!!!!!!

• posted

I need to know what will be happen went 240V drop to 200V.. What will happen to:

-amps (will it decreasing?) -kilowatt (will it decreasing?) -appliance (any effects?)

why this is happen?

pls reply to me as soon as possible.. i need to know.!!

• posted

Depends on the load and, to an extent, whether it is a dc or ac supply.

For a purely fixed-value resistive load, the amps and kilowatts will decrease and the load will just not give out as much heat. This is a little more complicated than that with loads which have resistances that change with the current flowing throught them - eg lamps. They typically will take more current and hence more kilowatts than simple Ohms Law would predict.

For an appliance which compensates for supply voltage, eg with a switched mode power supply capable of taking this range of supply, the amps will increase, the kilowatts will remain much the same and the load will show no obvious difference.

For an appliance not designed to take this range of supply, eg containing certain types of motor or power supplies that are not designed for this range - the amps will typically go up and then up and then up. The kilowatts will go up and then up and then up. The smoke will then go up and then up and then up.

Why does these things happen?

A purely fixed value resistive load simply obeys Ohms Law, so as the voltage drops, the current drops and so does the kilowatts.

A resistive load with a resistance that varies with amps obeys Ohms Law, but using the value of resistance that will be present for that much current flowing. The kilowatts will decrease with decreasing supply voltage - but not by as much as might be expected by simply considering the power taken on full voltage.

A compensating load, eg a switched mode power supply, has feedback built in - so that it automatically increases the average current if the average voltage falls. The kilowatts thus roughtly remain constant.

A load operated outside its designed range may try to compensate but may not be able to handle the continuous extra current that is needed or may simply go into a non safe area of operation for which it wasn't designed. Under these conditions, either something overheats and dies - producing smoke, flames etc, or efficiency drops greatly, leading to overheating, smoke and flames.

So, if you want to be more specific on what you are interested in as a load, do write again.

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