Fan connected to a power supply

athcerr

Joined Jun 11, 2021
22
Hello everyone;

I have a 12V DC, 80W fan, and I want to power it using a power supply that can output (in DC) 0 to 30V and 0 to 4A.

When the fan is connected to the power supply, the maximum current that can be obtained does not exceed 3.98A, which is normal since the maximum current that the power supply can supply is 4A. But the maximum voltage that can be obtained does not exceed 4V, whereas the fan should be supplied with 12V.

Can you explain to me what the problem is, and if I will use the XH-M401 voltage regulator can solve the problem? Please, note that the characteristics of the XH-M401 voltage regulator are:

• Supply Voltage: 4-40V To 1.25-36V
• Max output current: 8A (more than 5A for long time use,need Fan if over 5A), When reach maximum output current 8A, need to add fan. Long term work recommended about 5A
• Chip: switching regulator Regulating chip XL4016 with Over current protection, Over temperature protection,Short circuit protection
• Max power: 200W,Conversion efficiency: 94%,Switching frequency: 180KHZ
• Voltage regulating mode: PWM modulation

Jon Chandler

Joined Jun 12, 2008
1,071
Your fan draws 80 watts. You don't state the wattage it can supply, but it can supply a maximum of 4 amps over some range of voltage but it looks like the support can only supply 4 amps over a very small voltage range. When you try to draw more wattage than it can handle, it reduces the voltage to protect itself.

To supply a fan drawing 80 watts at 12 volts (=6.67 amps), you'll probably need a power supply capable of supplying 10 amps or more to handle the starting current.

The long and short of it – the power supply needs to supply more watts at the rated voltage than the fan draws. Period.

The converter you posted is a BUCK converter – it decreases voltage. A BOOST converter raises voltage, but reduces the current available.

Input power (volts × amps) must ALWAYS be greater than output power. Always.

crutschow

Joined Mar 14, 2008
34,689
Fan requires a minimum of 80W / 12V = 6.7A
Power supply can deliver a maximum of 4A.
Obviously basic incompatibility, as noted by Jon.

athcerr

Joined Jun 11, 2021
22

So, as I understand it, the current flowing in the circuit is not governed by the power supply, but by the fan.

To run the fan at 12V, the power supply must supply a current of 6.7A, but since the maximum value it can supply does not exceed 4A, the voltage remains below 12V.

Just out of curiosity, if the power supply delivers 4A at 12V, what could damage it?

crutschow

Joined Mar 14, 2008
34,689
if the power supply delivers 4A at 12V, what could damage it?
Any number of things.
Don't understand what you are trying to determine.

MisterBill2

Joined Jan 23, 2018
18,986
The damage caused by overloading a power supply is usually caused by heat. Which parts generate the most heat depends on the design of the power supply, but excess heat is able to damage most varieties of electronic components.

Joined Jan 15, 2015
7,546
Just out of curiosity, if the power supply delivers 4A at 12V, what could damage it?
Overloading it. You have an 80 watt fan designed for 12 VDC. So 80 watts / 12 vdc = 6.66 amps as was pointed out. You are well exceeding your supply capability and overloading it so the voltage out drops. Good supplies have protection against overload and apparently your supply doesn't. What could damage it? Overload can damage it and you are overloading it.

Ron

athcerr

Joined Jun 11, 2021
22
Any number of things.
Don't understand what you are trying to determine.
The aim is to run the fan at different speeds to characterise it (to determine the air flow rate blown as a function of the electrical power consumed), but the power supply I have apparently does not allow it to supply the rated power of the fan, I can just get low air flow rates associated with low electrical power.
You've told me that the problem is with the power supply, the power it can handle with this fan is low.
My question about what can damage it is just to find out more and add to my limited knowledge of electricity .