What is the difference between a AC-DC power supply and a AC-DC switching power supply

Question

I need a power supply for 200W 48vdc brushed motor. It will run at 2300 rpm and need 5 amps to generate 150 in-lbs torque. Will both AC-DC and AC-DC switching power supplies work. If both will work is one preferable?

Thanks, henrylr

Answer 1

• A power supply is a device that supplies power
• Usually (not always) the output voltage of a power supply is lower than the input voltage (for example: input = 240 V, output is 48 V)
• Usually a power supply converts AC into low voltage DC (for example: input = 240 V AC, output is 48 V DC)
• Some power supplies a are a "switching power supply", that means electronics are used to convert the power using high frequency (for example, 100 kHz) switching. This results in a more efficient and cheaper power supply.
• The alternative to the "switching" power supply is the "linear power supply" which uses a low frequency transformer (50 or 60 Hz mains AC) and a "linear regulator" (can be a switching regulator as well though). These supplies are heavy due to the large low frequency transformer and expensive (more material is needed).
• If you buy a new 200 W, 48 V AC to DC power supply today then this will be a switching supply. Non-switching supplies do exist but you will pay more and for powering a motor, a switching supply is perfectly fine.

Do realize that connecting the motor directly to the power supply might not work, the motor might draw a very high current when starting up. Generally a motor controller is used between power supply and motor.

Your 5 A motor is also too much for a 200 W, 48 V supply. A 200 W, 48 V supply can only deliver 200 W / 48 V = 4.17 A which is less than 5 A. You might need at least a 250 W supply.

It is good practice to use an even higher rated supply so for example 300 W, 48 V. Such a supply can "easily" deliver 5 A (while a 250 W supply would be struggeling).