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Load at the output of a power supply board

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Yac:
Hello everybody,

I have to set up a test bench to test two power supply boards, the first one provides a voltage of 24V (50W) and 48V (200W) and the second one provides a 5V (65W), +12V(7W) and -12V (7W).
I have to measure these voltages with a voltmeter at nominal load.

So, what load can I put on each output ?
Should I use a thermal radiator ? If so, how to choose the type of radiator.

Thank you in advance.

ledtester:

--- Quote from: Yac on September 03, 2019, 06:21:19 am ---So, what load can I put on each output ?

--- End quote ---

Usually DC power supplies are tested with an electronic load.

Otherwise any resistive load will work, such as power resistors and incandescent lamps.

Given the voltage and nominal wattage of a power supply, do you know how to compute the resistance required to draw the nominal power?


Yac:
Thank you for your help.

An electric load is a little expensive for what I want to do.

To calculate the resistance value I think it is necessary to use the ohm law.

But I don't know if the resistance will heat up a lot and if I have to use a heat sink to dissipate the heat.

For example, for the 48V output, I have a current of 4.2A, if I use a power resistor of 12 Ohms, 200W, Do I need a heat sink ?

ledtester:

--- Quote from: Yac on September 03, 2019, 07:16:45 pm ---An electric load is a little expensive for what I want to do.

--- End quote ---

You can get inexpensive electronic loads circuits on ebay/aliexpress.

This is a good one that works up to 30V and meets its advertized specs:

https://www.aliexpress.com/item/32776310672.html

This is another popular one which works at higher voltages, but you'll need to get two to test your 42V, 200W supply:

https://www.aliexpress.com/item/32916595565.html


--- Quote ---For example, for the 48V output, I have a current of 4.2A, if I use a power resistor of 12 Ohms, 200W, Do I need a heat sink ?

--- End quote ---

A power resistor is a resistor mounted on a heat sink. If the resistor is rated for 200W then there shouldn't be any problem.

How long do you have to test the supplies for? The power rating on a resistor is for continuous use. If you are only connecting the power supply for a short time you can get by with a lower rated resistor.

Yac:
Thank you for these ideas

The tests must be done automatically, I think these loads are not appropriated because I have to control the measuring devices via ethernet.

In fact, I don't know how long the tests will last, so I can't take the risk of choosing a lower rated resistor.

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