Hello.
When choosing the PSU, one should take into account such parameters as:
- output voltage 12 or 24V DC,
- the current that the PSU should be able to supply.
The current efficiency of the power supplies should not be less than that of :
- 20A for 24V power supply.
- 41A for 12V power supply.
Current efficiency can be estimated.
It depends on your components.
The most energy-intensive are heat bed, and hot end.
If you do not know the energy demand of these elements you can easily calculate it.
For this purpose, measure their resistance.
Knowing the supply voltage and resistance you will calculate the current that will flow when the heater is switched on at full power.
For example, in my printer the resistance of
the hot end heater is
15,2Ω, the resistance of
the heat bed heater is
3,2Ω. The power supply in my printer supplies 24V DC.
Heat bed current is: 24/3,2 = 7,5A
Hot end current is: 24/15,2 = ~ 1,6A
In the balance sheet, the power consumed by other components such as stepper motors, fans and control electronics should also be taken into account.
The PSU should also have a reserve so that it does not operate at full power at maximum load.
Estimated for motors, you can assume 1.5A per motor, and for fans it's different. My fans consume about 0.1A each and are powered by 12V DC voltage.
Of course, these considerations are approximate and everyone who is familiar with things knows how to approach them.
Individual components are supplied with different voltages and a few more calculations are needed to get to know the current drawn from the main 24V power supply.
The considerations are intended only to explain the principles of estimating the power demand.
