What is the difference between star and delta connection for rotor of slip ring motor?

Question

slip ring motors have stator with star connection and star or delta connection in rotor, and the resistance starter in star connection? waht is the difference?

I know that if I connect star Iline= I phase, but when I connect delta I line= 1.7 I phase, so why I connect delta for rotor, and for carbon brushes and resistance starter, what is the difference, if the rotor connected delta or star?

Answer 1

Slip ring motors are internally star connected with one end of each of the three windings connected to a slip ring. That allows series resisors to be externally connected through the three slip rings. Series resistors with a delta connection would require six slip rings and a more complicated contact arrangement in the resistance starter.

If the rotor windings were internally delta connected with the three connections brought out to three slip rings, external parallel resistors could be connected through the slip rings. I don't know what motor characteristics that would provide, but I am sure that if it was a useful arrangement, it would be described in electric machinery text books. I don't believe that such an arrangement is described.