Passenger Trains > Dynamic Brakes and High Speed

I was running an Acela train on my Mircosoft Train Simulator and noticed no dynamic brakes. Is this true with the real thing. Also, how accurate is this simulation? It seems that Marias Pass is more difficult.

grande473 Wrote:
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> I was running an Acela train on my Mircosoft Train
> Simulator and noticed no dynamic brakes. Is this
> true with the real thing. Also, how accurate is
> this simulation? It seems that Marias Pass is more
> difficult.
>

I think since the Acela is an integrated trainset the braking is blended by the computer automatically.

The default Marias Pass that comes with MSTS has some less than realistic grades...There are some freeware alternative versions that are more realistic. Check out www.train-sim.com, they have a large collection of stuff available.

The Acela has an electric locomotive, and electric locos don't have dynamic brakes, they have regenerative braking, which puts power back into the catenary. I think the acela does have regenerative braking, but my source who ran Amtark's simulator doesn't remember for sure.

The Acela has regenerative and dynamic brakes, and one can see see that in the display screen in the cabs.
Like all regeneratuve brakes, if the catenary has no demand for the power put back in by the braking effort, the power is diverted to dynamic brake resistor grids atop the roof. A catenary will "demand" power if there is another locomotive or EMU in the same section of wire that is not coasting or braking. If there is no other train demanding power, the power is diverted to the locomotive's grid of resistors.

The dynamic/regenerative brakes are blended with the air brakes. The locomotive engineer moves the handle to a service brake position that simulates a certain brake pipe reduction, say 10 pounds. Then, the software on the Acela generates a corresponding regeneratic/dynamic brake effort. The trainline brake pipe is also reduced, but the reduction is not completely 'relayed' to the brake cylinder as long as the software detects sufficient dynamic/regenerative braking. If the regenerative/dynamic brake effort is not enough, then air brake cylinder pressure increases to compensate. If dynamic/regenerative brakes fail or fade out, then the air brake cylinder pressure takes over completely.

Unlike GE and EMD diesel-electrics, the grids are not force-ventilated by blowers. The resistor grids are just bolted onto the roof. This arrangement is typical for EMU's, such as the M-2, and electric locomotives, such as the AEM-7.

Riding BART frequently I have wondered what their braking system might be. There are no grids visible on the trains. Do they have regenerative equipment plus mechanical?

Thanks for the info. Since I have never been in that part of the county I wouldn't know. The Acela tests at the test track east of here (Pueblo) were secret.

As was stated earlier the Acela power cars have both regen and dynamic. The dynamic brake resistors on the Acela power cars are not on the roof but are in a block within the locomotive machine room. There is a blower that blows air up through the block and out through a vent in the roof. The engineer cannot control the regen or dynamic. The brake computer controls the compensation between the regen, dynamic, and air to give the engineer the brake rate he calls for by position of the brake valve. The AEM-7 DC, and ALPs have only dynamic and the resisters on the roof use the wind for cooling. The AEM-7 and ALPs give the engineer the option of dynamic only without the use of the air brake handle. The AEM-7AC has both regen and dynamic but still uses the roof mounted resistors with natural cooling. The HHP-8s are the same as the Acela power cars.

"electric locos don't have dynamic brakes, they have regenerative braking"-- oops.

Locomotives that run under AC catenary can now have regenerative braking because they have inverters? In earlier days, when AC-catenary locomotives had DC motors, they never had regenerative brakes? Anywhere in the world?

>Locomotives that run under AC catenary can now have regenerative braking because they have inverters? In earlier days, when AC-catenary locomotives had DC motors, they never had regenerative brakes? Anywhere in the world?

It depends on what the railroad operator bought.

The GN used AC in the trolley wire and had regenerative braking on their locomotives, even though they had DC traction motors. This is because the conversion equipment (M-G sets, synchronous converters) is "bi-directional"; it will convert AC to DC and vice versa. The VGN EL-2Bs also used rotating conversion equipment, as did the GN W-1s, and both had regenerative braking. However, the VGN EL-Cs (E-33s) had dynamic brakes because, having ignitron recrifiers, there was no equipment to convert the DC to AC.

Neither the PRR nor the NYNH&H had electric braking, with the possible exceptions of the E-33s. The E-44s had provision for dynamic brakes, but I don't know if they were ever used.

>Locomotives that run under AC catenary can now have regenerative braking because they have inverters? In earlier days, when AC-catenary locomotives had DC motors, they never had regenerative brakes? Anywhere in the world?

It depends on what the railroad operator bought.

The GN used AC in the trolley wire and had regenerative braking on their locomotives, even though they had DC traction motors (early 1920s). This is because the conversion equipment (M-G sets, synchronous converters) is "bi-directional"; it will convert AC to DC and vice versa. The VGN EL-2Bs also used rotating conversion equipment, as did the GN W-1s, and both had regenerative braking. However, the VGN EL-Cs (E-33s) had dynamic brakes because, having ignitron recrifiers, there was no equipment to convert the DC to AC.

Neither the PRR nor the NYNH&H had electric braking, with the possible exceptions of the E-33s. The E-44s had provision for dynamic brakes, but I don't know if they were ever used.