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Re: Auxiliary Braking Unit or Brake Slug (TEBU)
Author: SP5103
Date: 02-10-2019 - 15:24
The SP TEBU units could run with a GP40-2 (new or rebuilt) mother on each end, in effect making them a pair of SD40-2 units without the wear and tear of a six axle on the track. Their primary assignments were in Oregon for the branches such as Tillamook, Coos Bay and Toledo - all either heavy trains, heavy grades and/or curves. The Arizona ore lines also got them. I believe Eugene would also send some sets out in helper service on the Cascades, something a GP40-2 by itself wouldn't be suited for (only 2000 hp rating at 10 mph if speed dragged down). But the SP TEBU units could also run with a single mother, in which case the mother powered both of the slug's trucks.
Typically, locos use a DC series traction motor - the power goes through the armature, then to the reverser, back to the traction motor fields, then back to the reverser, accounting for the four cables to each traction motor. To reverse the loco, the reverser changes the traction motor field polarity. The motors are then connected to the main generator/traction alternator in series, series parallel or parallel depending on the design and transition requirements.
For dynamic brakes, a transfer switch (similar to reverser) is used to rearrange the high voltage connections. All the traction motor armatures are connected in series with the resistance grids/cooling fan(s). The traction motor fields are connected in series with the main generator/traction alternator which operates at a minimum amount to create the excitation of the traction motor fields, resulting in the current through the armatures.
I looked at my SP TEBU print. In power, the TEBU would draw power from the adjacent mother(s), and slugs typically have their own electrical cabinet, reversers and switchgear. In addition, there is a second mu cable (different pin arrangement) which integrates the slug's electrical system with the mother's. In the case of the dynamic brakes, a slug typically has its own grid and cooling fans, but the traction motor field excitation for dynamic braking appears to be supplied through the traction motor cable jumpers from a single mother.
Typically, locos use a DC series traction motor - the power goes through the armature, then to the reverser, back to the traction motor fields, then back to the reverser, accounting for the four cables to each traction motor. To reverse the loco, the reverser changes the traction motor field polarity. The motors are then connected to the main generator/traction alternator in series, series parallel or parallel depending on the design and transition requirements.
For dynamic brakes, a transfer switch (similar to reverser) is used to rearrange the high voltage connections. All the traction motor armatures are connected in series with the resistance grids/cooling fan(s). The traction motor fields are connected in series with the main generator/traction alternator which operates at a minimum amount to create the excitation of the traction motor fields, resulting in the current through the armatures.
I looked at my SP TEBU print. In power, the TEBU would draw power from the adjacent mother(s), and slugs typically have their own electrical cabinet, reversers and switchgear. In addition, there is a second mu cable (different pin arrangement) which integrates the slug's electrical system with the mother's. In the case of the dynamic brakes, a slug typically has its own grid and cooling fans, but the traction motor field excitation for dynamic braking appears to be supplied through the traction motor cable jumpers from a single mother.
