OP
laurence6202
Most 3ph motors > 3kW are nameplated 400V delta/660V star in South Africa (and I think in the rest of the world). That means the windings can cope with and will deliver 3kW in 400V delta or 660V star. So using the arrangement below running it 660V star would give 17A winding current and 380V winding voltage the same as the delta connection, but with a reduced 17A line voltage as oppesed to the 30A line voltage in delta.
However the more common application for the star is to use it as a starting arrangement at 400V - with the figures in black on the left > therefore with only 10A line current as opposed to the 30A under delta. Of course the starting torque is also less, but this is OK for pumps where at lower speeds the torque required is less, so the star delta starters work well for loads that have low starting torque.
The nameplate is stating what the motor/windings are capable and designed to cope with, not necessarily how it is used.
If you had a 660V 3phase power supply you could use this same motor at the same power rating, but you would not have the option for lower starting current using the star delta arrangement, as the motor would have to run permanently in star.
![[ElectriciansForums.net] Star Delta Theory](/proxy.php?image=https%3A%2F%2Fdl.dropboxusercontent.com%2Fu%2F11809449%2Fstar-delta%2520connection.png&hash=a8cdcb0c36eef69fb34660f2bc3819da "[ElectriciansForums.net] Star Delta Theory")
However the more common application for the star is to use it as a starting arrangement at 400V - with the figures in black on the left > therefore with only 10A line current as opposed to the 30A under delta. Of course the starting torque is also less, but this is OK for pumps where at lower speeds the torque required is less, so the star delta starters work well for loads that have low starting torque.
The nameplate is stating what the motor/windings are capable and designed to cope with, not necessarily how it is used.
If you had a 660V 3phase power supply you could use this same motor at the same power rating, but you would not have the option for lower starting current using the star delta arrangement, as the motor would have to run permanently in star.
