>From an EMC perspective, line and neutral are treated the same as far as filtering is concerned; so there should be no change in emissions. Safety ratings of the components in a 120 V supply will also not be a problem as long as the three phase system has a neutral. The neutral on a 208 V Y-system ensures that each phase will be no higher than 120V above earth potential. Now if you are going to export this product, you will have to be concerned about the power system used. Some countries do not have a good earth connection or no connection at all. In that case, the phase to earth voltage can reach the full 208V. Dito these same senarios if you use 240V supplies on a 3-phase system.
If you use three, 120V power supplies on a 208 Y-system, you will have very high rms neutral currents (1.73 times the line current if I recall correctly) because the neutral contains the sum of the pulsed currents of the three supplies. If you use three 200-240V supplies from phase-to-phase, you will not have that problem. Again, dito these senarios with a higher voltage 3-phase system. Richard Woods Sensormatic Electronics [email protected] Views expressed by the author do not necessarily represent those of Sensormatic. > ---------- > From: [email protected][SMTP:[email protected]] > Reply To: [email protected] > Sent: Thursday, September 17, 1998 11:49 AM > To: [email protected] > Subject: Power Supply Design Question > > > > My company manufactures systems which incorporate power supplies from > various manufactures. Typically these supplies have ratings such as > 100V-140V/200V-240V and are designed to operate on a single phase input. > Some of my customers have the US 208V 3 phase power distribution which > gives you 208V phase to phase or 120V phase to neutral. > > My question is directed towards the power supply people on this list. > > Can ANY supply intended for 200-240V single phase be used at 208V phase > to phase (double phase). Would components (EMI suppression for example) > be placed between neutral and ground that would preclude the supply > from being used phase to phase? > > Would the use of these supplies in a phase to phase mode negate the > EMI/EMC performance? > > Thanks > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
