Overload Protection for Power Circuit of Locomotive:
1. To protect the main power circuit from overload, the thermal overload relays are used. 2. The overload is sensed by the overload relay which gives tripping signal to CB on occurrence of overload and the circuit is disconnected. 3. The overload relays and CB are provided in different sections of power circuit as shown in the above figure. 4. The overload relay OLR1 operates for overload on transformer side due to shorting of turns or any abnormal reasons. 5. The overload relay OLR2 operates for overload fault due to failure of diodes. 6. Similarly the overload relay OLR3 operates for overload fault on traction motor due to the flashover of traction motors.