Here is the specs: http://www.linmot.com/fileadmin/doc/Accessories_Controller/ps_S01-72-1000_e_recent.pdf

This power supply outputs adjustable DC. But why it has 3 line inputs and an earth??

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    \$\begingroup\$ ... Because sometimes industrial facilities need AC/DC conversion too. \$\endgroup\$ – Ignacio Vazquez-Abrams Jul 23 '14 at 1:54
  • \$\begingroup\$ ok but why 3 phase input for a DC output. 1 phase exists everywhere.. \$\endgroup\$ – user16307 Jul 23 '14 at 13:12

1kW is a high enough load that the balanced 3-phase circuit is an advantage.

Another advantage is that the filter capacitors need be much smaller for 3-phase, since a the output of a full-wave 3-phase bridge has less than 15% p-p ripple without any filtering at all. That would generally mean lower cost and longer MTBF for the power supply.

  • \$\begingroup\$ I never saw before generating a single DC output by using 3 phase alternating voltage. It is much more complicated to manufacture I guess. But whats the theory behind? How ,s that 3 phase converted to DC? \$\endgroup\$ – user16307 Jul 23 '14 at 13:18
  • \$\begingroup\$ In the simplest form it's just two addition cheap diodes and an input terminal, really almost nothing. A single phase full wave rectifier has 4 diodes, a three phase 6. If there is power factor correction it might be more expensive, but I don't see anything about PF correction on that datasheet. Many smaller (up to maybe 5-10HP) inverter motor controllers will work from 3-phase or (derated significantly) from single phase. \$\endgroup\$ – Spehro Pefhany Jul 23 '14 at 13:56
  • \$\begingroup\$ sorry but im not that deep in the subject. i might be repeating myself. but the link I sent u is a variable power supply which outputs dc voltage range for a motor drive. why on earth they just dont use a simple dc adapter to power a motor driver. why would one need 3 phases to obtain a dc output? i dont know how to ask it more clearly. \$\endgroup\$ – user16307 Jul 24 '14 at 0:39
  • \$\begingroup\$ Because the electric company will charge you extra for drawing from phases unevenly. \$\endgroup\$ – Ignacio Vazquez-Abrams Jul 24 '14 at 1:03

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