Hello everybody. I am a newbie.I have bought a driver BLD300C for my BLDC motor(300W). The problem is that I don't know the power of the driver because the current and Voltage are in range(picture below) so I can't calculate the P=U.I. The reason I need to know the Power of the driver is that I will buy a power source to supply the motor and need to calculate the watts total ( motor and driver) to buy a suitable power source. Please help me. Thanks for reading
The manufacturer assures that the driver is suitable for your motor:
But since this is the maximum value, it may be worth taking a more powerful driver
What is your motor specification?
In the driver datasheet, chapter 8, there is a list of supported motors. Check whether your motor is in the list too.
my motor is suitable with that driver but I need to know the power (watt) of this driver to buy a power source
The driver consumption is marginal. Find your motors peak current/power and add 20% to that
Thank you very much and how do you know that bro? 
The peak power? Without power supply for sure not by measuring it. 
So from the data sheet...
I mean the number 20%. Why not 30%, 10%,15%, something like that,...
Just pick a number. If you don't have good datasheets for your motor and driver and don't know the use case, it's difficult to answer. Peak can be high, but driver can throttle it. Some manufactures are rating motors like this:300W(500W peak), so it's giving you indication..
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What are you driving with this setup?
I doesn't matter what your motor can do, the driver has a peak current of 20.6A. So buying a 100A power supply would be pointless, a 20A-25A power supply will do.
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Obviously, but that would be already 1kW at 48V. We can help better if we know what that setup has to do.
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I intend to buy 1 power supply that can supply all my electrical equipment ( 2 motors (300x2=600W), 2 drivers(W), and some other electrical equipment(W). That is why I ask for the power of the driver so that I can sum up all of the power. And the power supply I buy should have a power > total sum. This is the power supply which I intend to buy. (48V 21A 1000W).
1000W > 600+ 2 driver( watt) + electrical equipment (watt) . This is my purpose.
It really doesn't work like that with these motors and drivers. You don't want to tell what are your motors running?
21A is a very odd specificaion. Is that the peak current or nominal current?
just a mobile robot can climb a wall
a nominal current
This is performance curve of some 300w motor.
If you are driving a light load, it may take 3amps. It can offer momentarily it's max performance at 15amps. Rated nominal current is 7.5amps.
So how did you end up calculating that you need 300w motor for your climbing robot? If your calculations are correct and that's what the robot needs to constantly climb, you are fine with 300W+10-20% heat lost in driver. But it could be more ore less or not constant.
So the answer is, you need about 200w for light load, 400w for nominal load, 800w for max load (not continous).
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you mean 300W+ 200W for light load , 300W + 400W for nominal and 300W +800W for max load. sorry for asking a stupid thing