EEE: Module 4 Flashcards
(8 cards)
DC Generator EMF equation
Eg = PΦNz/60A
Φ = flux per pole
P = no of pole
N/60 = speed in rps
z = total number of conductors
A = no of parallel paths
Synchronous Speed formula
120f/P
Three Phase Induction Motors
(Self-starting motor)
1) Three phase power flows through three phase stator windings
2) RMF created
3) RMF cuts rotor conductor bars
4) EMF induced in rotor (Faraday’s law)
5) Thus, rotor generates own magnetic field, opposing the cause (Lenz’s Law)
6) Rotor rotates in direction of RMF
7) Rotor doesn’t reach synchronous speed
8) Slip is necessary for induction
Synchronous Generator
(3-phase output generator)
1) DC supply to rotor windings
2) Rotor generates own magnetic field
3) Rotor rotates by external force (turbine)
4) Magnetic field cuts three phase stator winding
5) Three phase output emf induced in stator windings
Single Phase Induction motor
(Not self-starting)
1) Single phase power supply in stator creates pulsating magnetic field
2) An auxiliary winding is placed 90° apart from main winding
3) Capacitor is used to create a phase difference
4) RMF produced
5) Rotor cuts, EMF induced, Lenz’s law, rotor rotates
6) Auxiliary disconnected
Stepper Motor
1) Driver circuit/microprocessor connected to stator windings
2) Driver energizes one winding
3) Rotor (a permanent magnet) gets attracted to energized winding
4) Driver activates next phase
5) Rotor rotates in discrete steps
Universal motor
when the same current flows through both stator and rotor, the direction of torque remains unchanged even if polarity of current reverses. Hence works with both DC and AC supply
BLDC Motor
1) A controller circuit is connected to the stator
2) Based on rotor’s position controller switches ON/OFF pairs of stator windings in a sequence
3) RMF produced
4) Permanent magnets on rotor attracted and repelled by RMF
5) Rotor rotates synchronously
