Wire Leads

Can anyone explain the purpose of the three additional leads (T-10,T-11,T-12) on a Reliance 480v. 15hp 1750 rpm single speed motor. This is the first time I've run into this.

480v. connection...

T4 -----T7
T9 -----T6
T8 -----T5
T10-T2---L2
T11-T3---L3
T12-T1---L1

Thanks

Windings that are connected as shown (probably series) for 480V, and differently (parallel?) for 240/208?

Low voltage connections:

L1-T1,12,7,6
L2-T2,10,8,4
L3-T3,11,9,5
I've wired many 9 lead motors and it's the addition of the 3 leads that has me thinking. Reliance has these diagrams on thier web site but don't explain the purpose for a single speed motor.