Discussion related to commuter rail and rapid transit operations in the Chicago area including the South Shore Line, Metra Rail, and Chicago Transit Authority.

Moderators: metraRI, JamesT4

  by amtrakhogger
Do the current South Shore MU's utilize a motor/alternator for
auxiliaries or do they use an inverter? If so, is the aux voltage 480vac?

  by MikeF
The current MU cars have two auxiliary electrical circuits, one 115v AC (for the fluorescent ceiling lights and some onboard equipment such as the hand dryer in the lav and the convenience outlets) and one 75v DC (for propulsion control, doors, emergency lights, exterior lights, etc.). The DC auxiliary system is connected to the car batteries.

The cars employ a motor-alternator to convert the 1500v DC line current to 115v AC, and a solid-state transformer/rectifier to convert the 115v AC to 75v DC to charge the batteries. The newest cars (the 100-series) may use an inverter in place of the MA ... perhaps PRRGuy knows.

  by MikeF
In case anyone is wondering the same about the old "orange cars" -- as built, they used a motor-generator to convert the 1500v DC to 32v DC, which charged the batteries and provided power for propulsion control, car lighting and fans, and the conductor's signal bell. Pretty much everything else ran off the 1500v DC line voltage. When cars were lengthened, a motor-alternator was added which converted the 32v DC from the MG to 115v AC to power the fluorescent lights, as well as the air conditioner blowers on cars so equipped.