DIESEL LOCO - Propulsion Control Circuit

Propulsion Control Circuit

To move the locomotive, supply of Traction Alternator is send to traction motor through Power contactor, BKT, Reverser. This circuit is design to pickup above electro pneumatic contactor as and when require. In this circuit as per speed of locomotive two combination of traction motor are changed and during dynamic brakes traction motor convert into generator. Traction motor has following combination:

a) Series Parallel combination

b) Parallel combination

Reverser Contactor Control – To move the locomotive, keep reverser handle in desired direction, put ON GFCO-1&2 and on opening master handle reverser contactor coil will energize as per working control stand


MH(M)          NOI                  6-13A L/C/S

MH(M)          NOI                  6-13B R/C/S

RH(F)            NOI                  13A-8 L/C/S

RH (R)           NOI                 13A-0 L/C/S

RH (F)           NOI                 13B-0 R/C/S

RH (R)           NOI                 13B-8 R/C/S

Rev. Forward coil          Wire no. 8& 4

Rev. reverse coil             Wire no. 0 & 4

Series parallel combination- series power contactors coil will get

In this way S1, S21, S31 series power contactor pickup.

Rev(F)          NCI               8-8A 

Rev(R)         NOI                0-8A

BKR3           NCI                8A-8C 

BKR1           NCI                8C-8D 

ECS(Idle)     NOI                8D-8AA 

BKT(M)       NCI                8AA-8E

TR                NCI                8E-8F

GFC             NOI                8E-8F 

MCO            NOI               8F-8FF 

P1                 NCI                8FF – 8M 

P21             NCI                 8M-8Z 

S21        Contactor Coil    8Z-4 

P31           NCI                  8M-8G 

S31       Contactor Coil    8G-4

Parallel Combination (Ist transition) -When loco speed increases up to 41.5 km/h at that time TSSR energize and its contact 6AA-18A close and TR relay picks up through MCO, NCI 6-6AA and TSSR NOI 6AA-18A, due to which following changes will take place –

1. TR NCI 6E-6F open and GFC will drop.
2. TR NCI 8E-8F open and S 1, S21, S31 will drop.
3. TR NOI 8E-8L close and P1, P21, P31 will pick up through S31 NCI 8L-8S.

P2, P22, P32 will pick up in following way -

TR                    NOI                   8E-8L

GFC                 NCI                   8L-8R

BKT (M)          NCI                   8R-8K

MCO1              NCI                   8K-8KA

 S1                    NCI                   8KA-8U


 P2 contactor picks up(8U-4)              

MCO3            NCI           8K-8KB

 S21                NCI           8KB-8W

 P22 contactor picks up (8W-4)

MCO2           NCI           8K-8KC
 S31               NCI           8KC-8V P32

contactor picks up (8V-4)

As P32, P2 NOI (6D-6F) closes than GFC will pick up.

As P32 picks up its NOI (8E-8K) will close in parallel to P21, P31 NOI (8E-8K) and P2, P22, P32 supply will maintained.

In this way all six parallel power contactor pickup.

Throttle Not Responding to Loco/Load Meter Not Showing Current 

Precaution To Be Taken Before Wedging GFC:-

1. Ensure that current available in wire no. 6 (If BKT are change its position from braking to motoring it means current is available in wire no.6)

2. Ensure that cranking contactors are in open condition.

3. Ensure that BKT is in motoring position.

Precaution To Be Taken After Wedging GFC:-

1. First notch current will be excess, so in order to avoid the jerk on the  Loco, First open the MH then release loco brakes.

2. Parallel transition will not come, take manual transition.

3. Whenever GR/GFOLR operate bring throttle to idle immediately.

4. Do not use dynamic brakes.