1. CHAPTER V Motor Drives Motor drive systems definitions
Review of motor principles
Mechanical Requirements of Motor Drives
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

2. Electric Motor Drives
DEFINITION: Electric drives for motor is used to draw electrical energy from the mains and supply the electrical energy to the motor at whatever voltage, current and frequency necessary to achieve the desired mechanical output.
General arrangement for variable speed drive.
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

3. Example of Motor Drive System: Air Conditioning System
Three Main Elements of Motor Drives:
Electric Motor (DC, AC, SRM, Stepper)
Load Type
Control
Requirements of Drives:
Variable speed
Controllable Torque
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

4. Motor: Review of general principles
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

5. Flux in C-core
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

6. Air-gap flux densities
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

7. Evolution of motor geometry
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

8. Torque Production
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

9. Mechanical System requirements for drives: Linear motion
f e
f L x
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

10. Rotating motion f r torque 
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

11. Motor and load interactionTL
Tem
Jeq m
Jeq = combined load–motor moment of inertia
m = motor speed (rad/s)
TL = load torque
Tem = motor torque
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

12. Example(1)
Motor
Load TL
Tem
Jeq m
Jeq = combined load–motor moment of inertia
m = motor speed (rad/s)
TL = load torque
Tem = motor torque
Using the motor-load structure as above, assume the motor has a combined inertia of 0.058kgm2. The load torque is negligible. Calculate the required electromagnetic torque if the speed is to be increased from standstill to 1,800rpm in 5 sec.
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

13. Example(2)
The speed profile of the rotating system shown in previous example. (Jeq=0.058kgm2) is shown below. Assume the load torque is 5 N.m. Calculate and plot, as a function of time the electromagnetic torque required from the motor
0.2
0.1
0.3
0.4
0.5
t(s)
speed
(rad/s)
300
–300
Section B
Section A
Section C
Section D
Section E
Section F
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

14. Torque and Power T d
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

15. Friction Friction within motor and load appose rotation Examples:
Bearings (to support rotating structure)
Air (drag/windage)
Ditction (friction at zero speed)
Moving objects:
Coulomb friction (independent of speed)
Viscous friction (increases linearly with speed)
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB

16. Load Types Centrifugal (squared) Torque
Load torque is a function of speed
Example: Fans
Torque
Speed
Constant Torque
Load torque is independent of speed
Example: Low speed hoist, elevator
Torque
Speed
Power Electronics and Drives (Version 3: 2003): Dr. Zainal Salam, UTM-JB