• Feds to Investigate MBTA Safety

  • Discussion relating to commuter rail, light rail, and subway operations of the MBTA.
Discussion relating to commuter rail, light rail, and subway operations of the MBTA.

Moderators: CRail, sery2831

  by BandA
 
I thought in the 2015 incident the operator Jerry-rigged the deadman, so either they failed to un-rig the deadman or the deadman switch was defective and they never fixed it!
  by CRail
 
BandA wrote: Tue Jun 21, 2022 4:19 pm I thought in the 2015 incident the operator Jerry-rigged the deadman, so either they failed to un-rig the deadman or the deadman switch was defective and they never fixed it!
Neither is the case. The deadman wasn't "rigged," it was held down. The train was not under power as it rolled, the fact that 01502 was the lead car again is nothing but a coincidence.
  by jwhite07
 
Anyone know the nature of this "battery failure"? Was it defective battery that prevented the car from operating, or was it battery failure like smoke, flames, Roman Candle kind of battery failure?
  by Commuterrail1050
 
No smoke or flames that I’m aware of. However, I did see a picture of the affected car dark which tells me that it couldn’t move because of the loss of battery power. Not 100% sure and I’m not stating this as a fact.
  by dieciduej
 
Commuterrail1050 wrote: Wed Jun 22, 2022 8:37 am No smoke or flames that I’m aware of. However, I did see a picture of the affected car dark which tells me that it couldn’t move because of the loss of battery power. Not 100% sure and I’m not stating this as a fact.
Not sure how it works on transit cars but I use substation applications the batteries provide power to the relays and control circuits. So if there is a loss of AC power the control circuits are still powered. On transit cars the control side is low voltage, I wouldn't want 600 volts on the hand controller, so if you batteries are flat your flat. Plus the batteries provide emergency lighting.
  by Disney Guy
 
When the train is shut down for the night or whatever, and power sources switched off, it relies on the hand brakes being set or the service brakes defaulting to at least a partially applied state or chocks in place at the wheels or friction between the wheels and other related moving parts, bearings, etc. to prevent rolling downhill. The deadman control and reverser key do nothing.

In the 2015 (was it that long ago?) incident with the runaway Red Line train, the holding down of the controller handle other than with the operator's hand is the same thing as (is called) rigging it.

Modern transit cars have low voltage control circuits. Older "conventional" equipment (for example with K controllers) have all 600 volts of traction power below the controller handle. Also up to 600 volts measurable everywhere a circuit is broken such as at a switch in the off position or at a burned out light bulb. This sometimes unexpectedly high voltage as measured by a sensitive meter, drawing just a few milliamperes, is called open circuit voltage.

With DC traction power, motor generator sets (rotary converters) were commonly used before solid state voltage converters were developed, that is before about 1960, to provide low voltage to keep on board batteries charged. This also isolated the control circuits from 600 volt power. I am not sure whether low voltage, say, 32 volts, may have been derived using series circuits including lighting circuits. If an incorrect bulb were used as a replacement then the battery charging subcircuit could give off incorrect voltage and possibly result in a battery explosion.
Last edited by Disney Guy on Thu Jun 23, 2022 6:14 am, edited 2 times in total.
  by chrisf
 
jwhite07 wrote: Wed Jun 22, 2022 7:43 am Anyone know the nature of this "battery failure"? Was it defective battery that prevented the car from operating, or was it battery failure like smoke, flames, Roman Candle kind of battery failure?
The Globe is reporting it as a likely battery explosion, which is really the only thing that makes sense.
https://www.bostonglobe.com/2022/06/22/ ... o-answer-t
One train set has been sitting dead at the Forest Hills storage yard for several days now, so I wonder why this wasn't brought back to the yard since then.
  by west point
 
Next qestion . What kind of battery? Especially if a battery explosion. If so battery charger might have contributed? Investigation needs to determine if a battery fire happpened first.. Li ION?
  by BandA
 
If this was an explosion as everyone thinks, Ms. Battiston should be fired. This kind of government doublespeak is not acceptable.

Sounds like the problems Boeing had with the LiOn batteries in the 777. I think they had to redesign something to contain a battery explosion. Although why an electric subway car would need a LiOn battery - electric traction should be energy efficient enough that the LiOn battery would never pay for itself compared to lead-acid.

Simple battery failure should have no effect on a train that is connected to live third rail.
Last edited by CRail on Thu Jun 23, 2022 12:56 pm, edited 1 time in total. Reason: Unnecessary quotes removed.
  by BandA
 
We keep hearing about all the problems with the Red Line and the new Chinese railcars. Don't hear anything bad about the Orange Line yards or the Hawker-Siddley ~1979 Orange Line cars (except for rust and years ago when they were having trouble keeping up with failed traction motors)
  by typesix
 
BandA wrote: Thu Jun 23, 2022 8:53 am Simple battery failure should have no effect on a train that is connected to live third rail.
Yes it would. Previous post stated control circuits are low voltage. The low voltage is supplied by the battery, charged by the car. It is a safety that if the battery is dead, the control circuits cannot be activated and therefore a disabled car. The questions now are was the battery a lithium ion or the traditional lead acid, both of which can explode under the right conditions; and was the battery charger working properly?
  by BandA
 
I don't know how they designed this in China, but the low voltage should be available from the charging circuit which is powered by the third rail. If the battery won't accept a charge or is disconnected the low voltage should still be available. If the battery develops a dead short then of course the circuit breakers should trip and low voltage would not be available.

Interesting corollary: the older Toyota Highlander Hybrid, starter is connected to 12V lead-acid battery. If the 12V battery is discharged it will not start even with the LiON battery fully charged and connected to 240VAC charger. Poor design - won't charge the 12V battery unless car is moving I guess? There are two more corollaries about LiON battery cooling and regenerative braking failure but they are OT
  by typesix
 
Yes, low voltage may be available from charging circuit, but if battery is dead, the car won't move. It is purposely designed like this for safety reasons. You don't want to be rolling along and if the 600v drops out and the battery is dead, the control and other circuits won't be active. Another example is the PCC car, if the battery is dead, the car is disabled even if low voltage is available from the charger.
Believe all Toyota hybrids are designed this way, need 12v battery to be good for the car to move. Going from high to low voltage with enough power to engage a starter may require a big and wasteful resistor to pad down the voltage and handle the power needed.