Electricity in cars

Question 1

What components does an electric motor consists of?

Answer 1

• Stator
• Rotor
• Shaft
• Bearings
• Housing
• Commutator & Brushes (DC Motors)
• Air Gap

Question 2

How do motors work?

Answer 2

Converts electrical energy into mechanical energy

Current flows through the coils to create a magnetic field which interact with another magnetic field from the permanent magnet. The rotor spins and does mechanical work

Question 3

Compare AC and DC motors

Answer 3

Electrical supply: AC uses alternating current from grid, DC using direct current from battery

Commutation: DC uses commutators and brush, AC doesn’t

Magnetic field: AC produces a changing magnetic field, DC produces a rotating magnetic field

Speed control: Easier in DC motors

Starting Torque: High in DC motors for heavy duty applications

Efficiency: DC Motors are more efficient are lower power levels, AC higher for high-powered applications

Maintenance: AC requires less maintenance as it doesn’t use commutators or brushes

Question 4

What is the difference between a self-commutated and externally commutated motor?

Answer 4

Self-commutated: Motors uses commutators and brushes to manage current flow and don’t require external devices

Externally commutated: Rely on external devices to manage current flow i.e. inverter or variable frequency drive

Question 5

What are the differences between Salient Pole and Non-Salient rotors?

Answer 5

Structure
Salient - Poles project outward
Non-Salient: Smooth cylinder with uniform winding

Efficiency
Salient: High efficiency at low/medium speeds
Non-Salient: High efficiency at high speeds

Applications:
Salient: Used in hydroelectric generators
Non-Salient: Steam and gas turbines