Delta to Wye motor connections

[John2121]

I could use a bit of advise. I'm not use to delta to wye wiring required on the type of starters that we are going to be using. First they are large 350hp at 414 amp. i understand that i take dual feeders to the starter and dual feeders from the starter to the motor. How do I size the feeders correctly folks? (FLA x 1.25 x .58) (.58 derating factor for the Delta to wye.?)is a formula I was told to use. Do I use it on both the primary side of the starter and secondary?

Any help woould be apreciated.

 

[DanDel]

Check out NEC Article 430.22(C), for starters (no pun intended).

 

[davidbeach]

The total ampacity ahead of the starter is the FLA x 1.25 number. The 0.58 multiplier is for each of two sets of conductors between the starter and the motor.

 

[John2121]

Than you both for replying..Is there two set of leads leading to the starter also?..

Thanks again

 

[davidbeach]

A FVNR (Full Voltage Non-Reversing) starter, the most common type, has three connections between the starter and the motor; each connection may require more than one conductor for ampacity reasons. Each of these connections is made to one end of each winding in the motor; the connection at the other end each winding is made in the motor terminal box. For this it matters not whether the motor windings are wye or delta connected internally.

When using a wye-delta starter all six winding ends are brought from the motor to the starter, so there are six connections rather than three, and it may also take more than one conductor per connection. In the wye-delta starter the starter starts the motor with one phase connected to one end of each winding and shorts the other end of all three windings together, making a wye connection. Then in run mode, it connects the windings in a delta. What happens in between the modes depends on whether it is a closed transition starter or an open transition starter.