HE-7531 - Hybrid Electric Locomotive: Dynamic Braking Systems
HE-7531HYBRID ELECTRIC LOCOMOTIVE
SYSTEMS CUTAWAY · TRACTION & DYNAMIC BRAKING
LIVE SIM--:--:--
01

LIVE SYSTEM CUTAWAY

blend diesel/electric · on the brake, the pack drinks first and the grid takes the excess · hover any system to inspect

CUTAWAY · HE-7531

Hover a system to inspect it live.

Blend the source, raise the throttle, then throw the brake.
READY - pack at 64%. Blend the source, pull the power, then throw the DYNAMIC BRAKE - pack drinks first, grid takes the rest.
MECH DRIVE MAIN BUS · 600 V DC 7531 HE-7531 M M TRACTION MOTORS · 2 × 900 kW PRIME ENGINE GEN FUEL BATTERY PACK BMS 1.2 MWh MAIN SWITCHGEAR GEN GRID DB CONTACTOR DYNAMIC BRAKING GRID · 480 kW SPILL PATH
02

DYNAMIC BRAKING, STEP BY STEP

throw the brake in the cab above - the sequence lights up in sync
ENGINE GEN 600 V BUS TRACTION MOTOR M · MOTORED RESISTOR GRID 480 kW spill BATTERY PACK regen + blend source - 1.2 MWh I I I = current · E = back-EMF · V = bus voltage - this map mirrors the cutaway in real time
LIVE CIRCUIT MAP · CONTACTOR FOLLOWS THE CAB · BATTERY LINE SHOWS BLEND & REGEN FLOW
  1. 1

    CUT THE LINE

    Pulling the brake handle throws the main contactor: the engine's generator opens from the traction bus. The motor loses its supply, but it is still spinning at wheel speed.

  2. 2

    MOTOR BECOMES A GENERATOR

    Any armature spinning faster than its applied voltage wants to feed current, not drink it. With the bus disconnected, that current has nowhere to go until the contactor gives it somewhere.

  3. 3

    CURRENT RUNS BACKWARDS

    The contactor lands on the grid contact and the bus flips. Back-EMF drives current out of the motor and into the bus - the pack drinks first (cheap storage, up to 350 kW), and the contactor spills whatever is left up the roof feed line into the resistor bank. Electromagnetic counter-torque on the axles is the braking force itself.

  4. 4

    PACK FIRST, HEAT SECOND

    Energy the pack can't accept is dumped into the roof fins as heat - watch them climb toward cherry glow, heat shimmering off the roof. With a full pack the whole stop runs through the grid, and at 880 C the circuit auto-releases to protect it.

03

WHERE THE ENERGY GOES

no magic - conservation of energy, on a roof
KINETIC1/2 m·v² - the train's own motion and momentum
RESISTOR GRIDspill path - what the pack can't take, lost as I²R heat
HEATradiated and fanned away into the night air

When you pull the dynamic brake, the locomotive is not spending stored power at all - it is spending the train's own momentum. The motors flip into generators and the current runs backwards: the pack recharges first (up to 350 kW), and whatever it can't accept is dumped into the roof grid, leaving the system as heat. With the pack full, the entire stop runs through the grid - no friction, no worn brake shoes, just counter-torque and a roof that gets hot enough to glow.

SO WHY THE BATTERY?

The 1.2 MWh pack smooths engine load, carries the cab's auxiliaries, starts the prime mover, drinks the regen on every brake - and with the source-blend handle it can carry any share of the traction load, from a 50/50 split to full electric. What it is not, is the only brake: a hard stop needs more than the pack can drink, so the overflow always has the grid as a relief valve.

  • 880 °Cgrid auto-release temperature - the sim trips at this point too
  • 350 kWpack regen acceptance - everything above that spills to the grid
  • 1.2 MWhtraction pack - a full-electric pull lasts about 2 min before the diesel steps in