Wye Start results in a "Reduced Voltage" at the Stator Windings, and Delta Run results in full Voltage across each Stator Winding.
All the Motor's Winding Leads are brought out from the Motor, and connected to individual Contactors for Wye/Delta setup.
The 3Ø Motor Circuit is connected to the Motor via Mag Starter.
There was a detailed thread regarding this, but I can't remember when or where. It was here at ECN, but it may have been in this area (General Discussion), or the Theory and Applications area, or even the NEC area! May need to search them all. If I find it, I will post a link.
Feel free to ask additional questions if needed.
Scott " 35 " Thompson Just Say NO To Green Eggs And Ham!
Re: Y Start or Delta Run?#50867 04/14/0505:06 AM04/14/0505:06 AM
Wye (star) connections on a 3ph induction motor put the windings in series; to get from one phase to another, current passes through 2 or 3 windings, (dependant on the exact point on the cycle or phase)- which reduces the amps drawn; this is the reason for doing it on starting. An induction motor rpm is dependant only on the hz(cps) and the number of poles, (because the field of the stator revolves to match that of the generator in simple terms); less a certain amount of 'slip' by the rotor, usually reckoned at about 4% and which is essential for a pure induction motor to operate). An induction motor can draw up 6 times the amps pulled at full power, even if started unloaded, so a Y(STAR) start reduces the amps drawn and thus the size of the starter and wiring, and causes less of a shock to the mechanical parts of the driven machine too. Once up to speed, the motor is switched over,( by a special starter- these are usually automatic with a variable timer, but manual versions can be seen), to a Delta (ie coils wired directly across the supply) configuration for normal running. If left at the Y (star) wired configuration it can't develop its full potential HP. Hope this helps. Alan