Locomotives typically employ a large diesel engine to drive an alternator, or alternatively are powered by externally supplied electricity. The electric power from the alternator or the external supply is conducted to traction motors located beneath a platform of the locomotive. The traction motors convert the electrical power to rotational mechanical power, and, when engaged and supplied through the axles, drive the wheels. The rotation of the wheels by the traction motors drives the locomotive along its rails.
The electrical power supplied to each traction motor is controlled or regulated to avoid spinning or locking of any one of the drive wheels. In order to properly control the operation of the traction motors, as well as to control traction and wheel rotation during breaking, it is necessary to obtain a signal corresponding to the speed of rotation of each respective traction motor. Thus, traction motor speed sensors for each of the rotating axles are required.
A conventional locomotive traction motor includes a motor frame head, which forms part of the motor frame. The motor frame is typically connected to a truck (locomotive) suspension supporting a frame, and the truck is connected to a platform suspension supporting the platform via the locomotive main sills. The frame head is disposed in a generally vertical plane, and contains multiple ventilation openings.
The environment of a locomotive traction motor is extremely harsh due to temperature extremes, vibration and shock loadings, dirt and chemical contamination, and magnetic fields. Thus, a speed sensor design must maximize its survivability within its intended environment. Additionally, extensive labor, time, and costs are involved in installing one of these assemblies. Unfortunately, because of the harsh operating environment, however, the sensor itself requires regular replacement.
There is known in the art a traction motor speed sensor assembly that includes a housing which is attached across a ventilation opening on the motor frame head. A sensor portion to which the sensor itself is hard-wired, which is integral to the housing, is cantilevered from a base portion of the housing and extends through the ventilation opening toward the axis of rotation.