ME Power Electronics & Drives Solid state AC drives

1. AC drives
1. Introduction
2. Equivalent Circuit
3. Power flow diagram
4. Speed-Torque characteristics
5. Speed control-stator control
6. http://www.getgyan.com/show/1934/Stator_Voltage_
Control_of_Induction_Motors
7. http://www.powershow.com/view/e2c9-
ZjAyO/ELECTRICAL_DRIVES_powerpoint_ppt_pres
entation
http://www.scribd.com/doc/54947260/7/Stator-Voltage-
Control
http://ebookbrowse.com/practice6-scalar-control-of-
induction-motors-pdf-d78795114

2. 5.Speed control
• Stator Voltage control
• It is used for
• 1.controlling speed
• 2. control starting and braking behavior
• 3. to maintain optimum efficiency when
wide load range
• Dissipative method of speed control
results in less efficiency & rotor
overheating

4. Slip at maximum torque remains unchanged
since it is not a function of voltage.
Tmax reduces as input voltage reduces.
Since directly proportional.

5. • Torque is proportional to square of its
stator voltage.
• A 10% reduction in voltage causes a 19%
reduction in developed torque as well as
the starting and maximum torque.

11. 2. Advantages of an Electrical Drive
• 1. Smooth speed control
• 2. Four quadrant operation is possible
• 3. Can start and stop instantly
• 4. Wide range of speed control
• 5. Flexible
• 6. Reliable

12. 5. Equations governing motor load
dynamics
• Motor torqueT=TL+J(Əω/Ət)
• TL-Load torque
• J-Moment of inertia
• ω - angular speed
• The load may be either rotational or
translational

13. 6. Steady state stability