Railway workshops (loco sheds, carriage & wagon shops) run electrical drives for lathes, cranes, compressors, and other machine tools. AEE candidates are expected to know the common motor types used and how to select a drive for a given load.
Common Motor Types by Application
- Three-phase squirrel-cage induction motors — the default choice for constant-speed loads (pumps, compressors, fans, most machine tools).
- Slip-ring (wound-rotor) induction motors — used where high starting torque with controlled starting current is needed, e.g. cranes and hoists.
- DC motors — used in older variable-speed applications; largely superseded by VFD-driven AC motors in modern workshops.
- Variable Frequency Drives (VFDs) — now standard for speed control of AC induction motors, replacing older DC drive systems.
Starting Methods for Induction Motors
- Direct-On-Line (DOL) — simplest, but draws high starting current (5–7× full-load current); used only for small motors.
- Star-Delta starting — reduces starting current to roughly one-third by starting in star and switching to delta.
- Auto-transformer starting and soft starters — used for larger motors needing smoother, lower-inrush starting.
Content Status
Draft note, self-authored for the platform skeleton. Not yet cross-verified against the official RBE 14/2014 syllabus PDF — treat as study-aid only until verified.