DC MOTORS Construction & Types

1. DC MOTORS Construction & Types

2. Motors Everywhere! • The fan over the stove and in the microwave oven • The dispose-all under the sink • The blender • The can opener • The washer • The electric screwdriver • The vacuum cleaner and the Dustbuster mini-vac • The electric toothbrush • The hair dryer

3. More Motors . . . • The electric razor • Power windows (a motor in each window) • Power seats (up to seven motors per seat) • Fans for the heater and the radiator • Windshield wipers • Most toys that move have at least one motor (including Tickle-me-Elmo for its vibrations) • Electric clocks • The garage door opener • Aquarium pumps • Your TEKBOT In Short, EVERYTHING THAT MOVES uses some type of motor!

4. Important Concepts • How Motors Work • The Components of a DC Electric Motor • What’s inside the motor box? • The parts of the motor and what they do! • Motor Control • How to change directions • Concepts of Speed, Torque, Gear Ratio • Practical considerations • Noise, slippage, limits of operation: speed, torque

5. DC Electric Motors • Electric Motors or Motors convert electrical energy to mechanical motion • Motors are powered by a source of electricity – either AC or DC. • DC Electric Motors use Direct Current (DC) sources of electricity: • Batteries • DC Power supply • Principle of How Motors Work: • Electrical current flowing in a loop of wire will produce a magnetic field across the loop. When this loop is surrounded by the field of another magnet, the loop will turn, producing a force (called torque) that results in mechanical motion.

6. Motor Basics • Motors are powered by electricity, but rely on principles of magnetism to produce mechanical motion. • Inside a motor we find: • Permanent magnets, • Electro-magnets, • Or a combination of the two.

7. Inside a Toy Motor(Similar to TekBot Motor)

8. Toy DC Motor, cont. • End Views of Motor • Axle • Battery Leads • Axle will turn if connect battery leads to a 9V battery • Reverse battery leads and axle will turn the Opposite direction! • The white nylon cap on the motor can be removed to reveal…

9. A View of the Brushes • Inside the Nylon cap are the Brushes • Brushes can be made of various types of metal. • Their purpose is to transfer power to the commutator as it spins.

10. Inside the Motor, cont. • The Axle is the rotating part of the motor that holds the armature and commutator. • This armature is comprised of 3 electromagnets. (3-Pole DC Motor) • Each electromagnet is a set of stacked metal plates with thin copper wire wound around each. • The two ends of each coil wire is terminated and wired to a contact on the commutator. • Thus, there are 3 commutator contacts in all.

11. Inside the Motor, cont. • The final piece is the stator, a permanent field magnet. • It is formed by the motor enclosure and two curved permanent magnets (2 Pole: 1 North, 1 South) shown.

12. dcmotor A Two Pole DC Motor

13. dcmotor A Four Pole DC Motor

14. dcmotor Operating Principle of a DC Machine

15. dcmotor Armature of a DC Motor

16. dcmotor Armature Winding in a DC Machine

17. dcmotor Lap Winding of a DC Machine • Used in high current low voltage circuits • Number of parallel paths equals number of brushes or poles

18. dcmotor Wave Winding of a DC Machine • Used in high voltage low current circuits • Number of parallel paths always equals 2

19. TYPES dcmotor Based on the construction the DC brushed motors are classified in to DC seperately exited Motor DC self exited Motor Compound Motor.

20. dcmotor Separately Excited DC Machine RA + Armature Vf - Field Coil

21. dcmotor Shunt Excited DC Machine Shunt Field Coil Armature RA

22. dcmotor Series Excited DC Machine RA Armature Series Field Coil

23. dcmotor Compound Excited DC Machine Series Field Coil Shunt Field Coil Armature RA • If the shunt and series field aid each other it is called a cumulatively excited machine • If the shunt and series field oppose each other it is called a differentially excited machine