Title: Converting Volts & Amperes to Watts - 36V 1400mA & 72V 700mA: Calculate Wattage

Question

Hello, 36 V and 1400 mA = how many Watt is it? 72 V and 700 mA = how many Watt is it? Sorry for the strange question.

niewolno2 · Answer

36 X 1.4 how much is it? 72 X 0.7 is how much is it?

MACIEK_M · Answer

1V * 1A = 1W 1000 mA = 1 A. and all clear. :D We are talking about direct current and resistive loads.

we3rty · Answer

Such an example was given by someone else, and I supposedly corrected it and replied that you should also write wrong first, and then I will give you how much this person wrote, how much according to her it is.

niewolno2 · Answer

Then put your calculations here.

we3rty · Answer

U * I = P So it is 50.4W in both cases?

niewolno2 · Answer

And I don't want to be otherwise.

we3rty · Answer

How a miracle a person who knows electricity and probably electronics wrote that in both cases it is 56 W What would have to meet such a requirement to get 56W?

krzysiek_krm · Answer

Describe this point in detail. Perhaps this someone took into account the efficiency of the power supply, for example, it would be 90%.

we3rty · Answer

It is about the use of LED in the home krzysiek_krm you're right, it's probably about the efficiency of the power supply How is the efficiency of a power supply per watt calculated? U * I = P 36 * 1.4 = 50.4W 72 * 0.7- 50.4W Is the calculations good here? How does the power supply come, then it looks different? How is it calculated?

kblg13 · Answer

When you plug in the power supply, some power is emitted on it. The input power will always (at least a little) be greater than the output power, and the difference in input and output power results in wasted power on the power supply. Perhaps there was 56W at the input, and 5.6W was left on the power supply. Then the efficiency: 50.6W / 56W is actually 90%.

we3rty · Answer

How to find out that the input was 56W?
How to find out if there is 5.6W left on the power supply?
What kind of power supply would it have to be for it to come out or is it all given on the power supply?

If the efficiency of the power supply is 87%, how much would it be in the end?

kacpo1 · Answer

The current consumption should be indicated on the rating plate. Since the input power is 56W and the efficiency is 90%, the power supply will lose 56W x 10% = 5.6W. The efficiency depends on the design of the power supply and the load. It is impossible to give the model of the power supply based on the efficiency. With an efficiency of 90%, it is probably a switching power supply. Input power 56W, efficiency 87%, so 56W x 13% = 7.28W and so much less would be at the output.

we3rty · Answer

Thanks for the clarification.

Which would be better power supply:

36V and 1400mA
if
72V and 700mA

Is it better for the power supply to have a larger volt range and less amps or less volts more amps? Which would be more effective or efficient?

krzysiek_krm · Answer

This is a wrong question. Before, you wrote and the high-power LEDs are energized current , you need a power supply with a current efficiency equal to the current of light emitting diodes. The range of the output voltage must be such that your diodes fit there.

we3rty · Answer

I am asking pure hypothetical.

Let's assume it is a 70W LED

Would the power supply be better in this case

36V and 1400mA
if
72V and 700mA

I would not like to fully power the LEDs only in about 50W, e.g. with the attached potentiometer in the power supply (20W LED would have a spare), so in this case, which power supply would be better?

kacpo1 · Answer

Maybe it's better to start with reading about LED powering?
Exact parameters are needed, such as diode forward voltage and diode current. The power supply must be a constant current one, the voltage range of which is within the diode voltage and the current of which corresponds to the diode current.

we3rty wrote:
e.g. with an attached potentiometer in the power supply

With this LED power, the potentiometer is off.

krzysiek_krm · Answer

It is done completely differently. First, you choose the LED that interests you. You check in the documentation what parameters it has: current If and voltage Vf, usually a certain spread of this voltage is given for the current If, it results simply from the production characteristics spread. You buy yourself current LED power supply with the appropriate output current (Your If) and the appropriate output voltage range (must cover the Vf range of your diode, preferably with up and down reserve). If you want, you can buy a dimmable power supply. And that's it.

kj1 · Answer

The problem you raised cannot be explained in a few words

we3rty wrote:
Would the power supply be better in this case

36V and 1400mA
if
72V and 700mA

If the parameters of the power supply are given in this way, we are dealing with a voltage stabilizing power supply with a certain maximum current efficiency.
If the current capacity is exceeded, the protection will trip and most likely disconnect the power.

LED power supplies have the specified voltage range and current.
e.g.

Which of the power supplies listed by you will be the right one depends on how many, which and how connected LEDs the illuminator you want to power contains

Title: Converting Volts & Amperes to Watts - 36V 1400mA & 72V 700mA: Calculate Wattage

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