- 2082 Bhadra (new course) · 3 marks
BLDC motor construction and applications
Short answer
BLDC motor has a3-phase stator winding, permanent-magnet rotor, and position sensors (Hall) feeding an electronic inverter that produces trapezoidal back EMF for brushless commutation. Unlike an induction motor, the rotor has permanent magnets (no slip), needs an electronic drive, has no rotor copper loss, and offers higher efficiency. Applications include computer fans, hard drives, electric vehicles, and drones.
What are the constructional features of brushless DC motor? How is it different from induction motor? State two applications of BLDC motor.
A brushless DC (BLDC) motor is a permanent-magnet synchronous motor fed through an electronic inverter that switches the stator phases according to rotor position, replacing the mechanical commutator and brushes of a DC motor.
Constructional features
- Stator: laminated core with a 3-phase (usually star) winding, like an AC motor.
- Rotor: permanent magnets (ferrite or NdFeB) on the surface or inside the rotor; inner-rotor or outer-rotor types.
- Position sensors: Hall-effect sensors (or sensorless back-emf detection).
- Electronic commutator: 3-phase inverter controlled from the sensor signals; back emf is trapezoidal.
DC --> [Inverter] --> stator A,B,C --> PM rotor
^ |
+------ Hall sensors <--------+
Difference from induction motor
| Point | BLDC motor | Induction motor |
|---|---|---|
| Rotor | Permanent magnets | Cage/wound, induced current |
| Speed | Synchronous, no slip | Below synchronous (slip) |
| Supply | DC via electronic drive | Direct AC supply |
| Rotor loss | Almost none | Rotor copper loss |
| Efficiency | Higher | Lower |
Applications
Computer fans and hard disk drives; electric vehicles, e-bikes and drones (also inverter fans, washing machines).
✓ Answer checked by Claude Sonnet 5.5
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