OR Dynamic Brake

[derekmorton]

Hi Kevin,

I found a paper about inverters and eddy currents.

https://www.academia.edu/65535185/Inverter_Inductor_Circuit_for_Eddy_Current_Treatment_of_Ferromagnetic_Pieces

Compared to DC equipment the eddy currents in AC inverter and motors do not cause operational issues other than a heating effect.

[jbtower]

>However in high speed rail those same eddy currents are used to create a brake

We were talking about inverter braking.

What you are talking about is completely different.

https://en.wikipedia.org/wiki/Eddy_current_brake

Yes you were and if you reread what I posted you will see that I did explain how inverter braking works and also how an eddy current brake works as well. Also note that your comment "there are no eddy currents to worry about" is incorrect when in fact there are eddy currents in AC induction motors!

[landnrailroader]

Thanks guys, I knew how Dynamic Brake is supposed to work, I've run 1'=1' scale engines that had it. My question was just how to activate it in ORTS and now I find it works great.

Jerry

[derekmorton]

>However in high speed rail those same eddy currents are used to create a brake

We were talking about inverter braking.

What you are talking about is completely different.

https://en.wikipedia.org/wiki/Eddy_current_brake

[Erick_Cantu]

Correct. I was speaking in terms as the Sim is modeled (incorrectly or not) to avoid confusion when running the sim.

Ah, I gotcha. That makes sense.

[jbtower]

Ac machines have the dynamics available instantaneously as there is no eddy currents to worry about.
Most ac machines have the dynamics incorrectly and need to be fixed.

Dynamics with AC machines re set up in the inverters, so no switchgear.

In the operation of both GE and EMD A/C locomotives the A/C for dynamic braking is created by introducing voltage at a lower frequency than the rotation of the motor which induces currents producing a retarding force in the motor. The motor will in turn supply a voltage (by controlling frequencies) back to the inverter were it will in turn be converted to D/C and directed to the resistor grids. Like any A/C motor there are eddy currents but those will be cleaned up in the inverter. However in high speed rail those same eddy currents are used to create a brake (sometimes referred to as a Faraday's Brake) which creates a counter force and rapidly slowing the rotational forces.Hopefully this response is informative, I didn't want to bore anyone with frequencies, sines, cycles etc that unless your in the electrical industry can be difficult to understand!

[cuontv]

Other way around. The throttle must be reduced to idle for 10 seconds prior to placing dynamic brakes in set up. This has been erroneously modeled in most MSTS/OR equipment. The AAR controller is very clear about this:

Correct. I was speaking in terms as the Sim is modeled (incorrectly or not) to avoid confusion when running the sim.

[Erick_Cantu]

Yes, there are two ways to apply dynamics depending on how the controllers are set up and the type of control stand in the locomotive.

Also, applying the dynamic brake is not instantaneous after you come out of power. After you set the throttle to idle and select dynamics, you have to wait 10 seconds for the switchgear to changeover, then you can begin applying the brake. If you press the keys before that time period passes, nothing will happen.

Other way around. The throttle must be reduced to idle for 10 seconds prior to placing dynamic brakes in set up. This has been erroneously modeled in most MSTS/OR equipment. The AAR controller is very clear about this:



Also, from the GP38-2 operator manual:

Dynamic braking, on locomotives so equipped, can prove extremely valuable in retarding train speed in many phases of locomotive operation. It is particularly valuable while descending grades, thus reducing the necessity for using air brakes.

Depending on locomotive gear ratio, the maximum braking strength is obtained between 19 and 23 MPH. At train speeds higher than the optimum, braking effectiveness gradually declines as speed increases. For this reason, it is important that dynamic braking be started BEFORE train speed becomes excessive. While in dynamic braking, the speed of the train should not be allowed to "creep" up by careless handling of the brake.

To operate dynamic brakes, proceed as follows:

1. The reverser handle must be positioned in the direction of the locomotive movement.

2. Return throttle to Idle and hold it in Idle for 10 seconds before proceeding.WARNING


The 10 second delay must be accomplished before the braking handle is moved into SET UP position.

Braking delay occurs automatically. Do not misinterpret the delay as failure of the dynamic braking system.

It is possible for a sudden surge of braking effort to occur if the dynamic braking handle is open when the automatic delay times out.

3. Move the braking handle into SET UP position. This establishes the dynamic braking circuits. It will also be noted that a slight amount of braking effort occurs, as evidenced by the load current indicating meter.

4. After the slack is bunched, the dynamic braking handle is moved to control dynamic braking strength. As it is advanced out of SET UP, it will be noted that the engine speed automatically increases.

5. Braking effort may be increased by slowly advancing the handle to FULL 8 position if desired. Maximum braking current, limited to 700 amperes, can occur over a wide range of braking handle positions. This range allows braking effort to increase as train speed increases. The tendency is to hold train speed relatively constant for a given braking handle position when conditions result in less than the maximum allowable current.

[derekmorton]

Ac machines have the dynamics available instantaneously as there is no eddy currents to worry about.
Most ac machines have the dynamics incorrectly and need to be fixed.

Dynamics with AC machines re set up in the inverters, so no switchgear.

[cuontv]

Yes, there are two ways to apply dynamics depending on how the controllers are set up and the type of control stand in the locomotive.

Also, applying the dynamic brake is not instantaneous after you come out of power. After you set the throttle to idle and select dynamics, you have to wait 10 seconds for the switchgear to changeover, then you can begin applying the brake. If you press the keys before that time period passes, nothing will happen.

[R. Steele]

Dynamic Brake Increase use "period" --- Decrease use "comma" key -- sometimes ( and you would understand this better than me ) the throttle keys A & D control the dynamic brake ... depends on how the engine controllers are set up ( I think ? )

[landnrailroader]

Assuming that your motive power is equipped with it, how do you engage/disengage dynamic brake in ORTS.