Why 3ph power supply?

[ptonsparky]

What is the advantage of a three phase 400-500v AC to 24v DC power supply when the need is only 2 amps or less? Is it worth the dollars?

 

[synchro]

Do you know that it actually uses all 3 phases?

Most DC supplies nowadays rectify the AC input with diodes and then use a higher frequency switching supply because any transformers, capacitors, etc. can then be much smaller than with a straight 60 Hz supply. The ripple after a 3-phase diode bridge is much lower than with sngle phase and therefore requires much less filtering to get a given level of ripple. This is a big advantage with a linear supply operating at 60 Hz. With a switching supply operating at higher frequencies there is less advantage to be gained with a 3 phase input, especIally if the power level is relatively low.

 

[gar]

190627-0853 EDT

ptonsparky:

My guess is that a single phase input would be less expensive.

Three phase is less inherent ripple without filter capacitors. Depending upon your ripple needs three phase might use no capacitors, thus better 50 year lifetime.

Three phase probably would be better voltage regulation without electronic regulation on the output.

Less filter capacitance for the same ripple, but for low current supplies filter capacitance is inexpensive.

Three phase more expensive to wire up.

.

 

[Jraef]

The issue is that using a 400-500V auto-ranging power supply means you don't need another transformer (like a CPT) to step down the line voltage to feed the power supply input. Then 3 phase vs single phase makes the package more compact and less expensive because of needing less capacitance to smooth out the ripple. The mfrs feel that if you have 480V, it's a 99% chance it's a 3 phase source.

 

[junkhound]

What is the advantage of a three phase 400-500v AC to 24v DC power supply when the need is only 2 amps or less? Is it worth the dollars?

For a 50W 24 V supply, 3 phase is actually MORE complex. NO advantage, disadvantage.

Nowadays, a simple single phase supply with a switch mode PWM PFC front stage has 0.99PF and < 1% harmonics, a few millivolts ripple at a few dozen kHz on the 24Vdc. . A 3 phase PFC is more than 3X as complex as single phase for low power.

Why the 500Vac input, is that all that is available?

For $15, you can get a 240 Vac to 24Vdc supply that goes on a circuit board.

 

[milldrone]

The issue is that using a 400-500V auto-ranging power supply means you don't need another transformer (like a CPT) to step down the line voltage to feed the power supply input. Then 3 phase vs single phase makes the package more compact and less expensive because of needing less capacitance to smooth out the ripple. The mfrs feel that if you have 480V, it's a 99% chance it's a 3 phase source.

+1

At my facility, dealing with arcflash is a major concern so to make things easier to comply with the requirements, new installations use 24 volt controls. the new systems typically use 3 phase 480 to 24 volt power supply(s) in a separate cabinet from the 24 volt controls. Since there is no need for 120 volts in these installs the added cost of an additional transformer makes the the cost about the same.