Wheel slip however is very bad. Not only does it mean the train can stall if climbing a grade, but can cause extensive damage to locomotives or the tracks.
“Modern” locomotives have systems in place to deal with wheel slip (I say modern in quotes because the systems have been in place since the 1950s and has only been slightly improved since then). First and foremost, the locomotives control system is designed to detect wheel slip, either by measuring speed or electrical load of the traction motors and looking for a large difference or change between them. There will be slight variation due to differences in wheel diameter from axle to axle, but they should be close. If the speed on one traction motor is much higher or the electrical load of the motor is much lower, than the locomotive sets off a wheel slip alarm.
When that happens, the locomotive will immediately decrease power to the traction motors until traction is regained, then will ramp power up again until wheel slip is detected again, and will repeat this cycle until either the engineer lowers power, or traction allows for power to be fully reapplied without slippage. In older locomotives, it would decrease power to the whole locomotive, but in newer locomotives with individual motor control systems and A/C powered traction motors, the locomotive can decrease power to only the slipping traction motor while leaving power applied to the others.
The next system we will talk about is the locomotive sand system. Sanders on locomotives date back to the days of steam. Locomotives have massive sand storage boxes in the nose and long hood of the locomotive. They use compressed air from the locomotives air system to spray the sand through hoses and nozzles onto the rail ahead of the wheels. The sand, a very fine grained silica like sand, dramatically helps with traction.
This system must be manually turned on by the locomotive engineer on some older locomotives, but on many of them the sanders are automatically turned on when wheel slip is detected (or also when an emergency brake application is made to prevent wheel skids).
The last system I’m going to talk about is the rail blower system. Found on newer GE locomotives is the Air Rail Cleaner (ARC), which used high pressure air from the locomotives air system blown through a small nozzle angled on the rail to clean the rail ahead of the front axle of the locomotive. This will clear debris that could cause slippage, such as leaves or insects, off the rail, as well as blowing off excessive water, snow, or even frost off the rail head. This system can be automatically turned on, or manually in the locomotives computer.
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Негізгі бет Extreme Wheel slip - EMD G22W Class M6
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