- Dynamic Braking: where the motors become generators and feed the resulting current back. It classified into two categories:
2. Rheostatic Braking
3. Regenerative Braking
- Plugging: Generally plugging is applied by changing the phase sequence of the three-phase induction and synchronous motor.
REGENERATIVE BREAKING
The motors become generators and feed the resulting current into an on-board resistance. When the driver calls for brake, the power circuit connections to the motors are changed from their power configuration to a brake configuration and the resistors inserted into the motor circuit. As the motor generated energy is dispersed in the resistors and the train speed slows, the resistors are switched out in steps, just as they are during acceleration.
Even if the line is receptive, feeding power back to the supply grid may not always be possible, though, because of practical constraints in the design of the substation equipment, reverse flow detection relays in the supply grid (provided as protection in case of a fault in the 132kV supply system), improper phase match by the loco resulting in relays blocking the regenerated power, etc. The regenerated power therefore often gets used just by circulating in the OHE system and thereby getting used by other locomotives in the section. Because of this, regenerative braking bears fruit in busy sections where there are always some live locos. (In other railway systems, e.g., in Japan, although not in India, sometimes the regenerated power is just dissipated using large resistive loads at the substation or elsewhere.; Conversely when the system voltage starts dropping, it is an indication that the locomotive(s) on the section is/are not generating power and are instead consuming power (the normal case) in which case the normal power supply feeds energy back in to the OHE.
If at a speed N1, we reduce the frequency from f1 to f2 , then Sync. Speed reduces, and for the same motor speed N1, operating point shifts from P1 to P2 on regenerating portion with negative torque. Thus, regenerative braking is achieved, which is possible right up to near-zero speeds.
Even if the line is receptive, feeding power back to the supply grid may not always be possible, though, because of practical constraints in the design of the substation equipment, reverse flow detection relays in the supply grid (provided as protection in case of a fault in the 132kV supply system), improper phase match by the loco resulting in relays blocking the regenerated power, etc. The regenerated power therefore often gets used just by circulating in the OHE system and thereby getting used by other locomotives in the section. Because of this, regenerative braking bears fruit in busy sections where there are always some live locos. (In other railway systems, e.g., in Japan, although not in India, sometimes the regenerated power is just dissipated using large resistive loads at the substation or elsewhere.; Conversely when the system voltage starts dropping, it is an indication that the locomotive(s) on the section is/are not generating power and are instead consuming power (the normal case) in which case the normal power supply feeds energy back in to the OHE.
If at a speed N1, we reduce the frequency from f1 to f2 , then Sync. Speed reduces, and for the same motor speed N1, operating point shifts from P1 to P2 on regenerating portion with negative torque. Thus, regenerative braking is achieved, which is possible right up to near-zero speeds.