Smart Grids
Presented to : Dr. Madeha Mohamed
Made by:
index
The meaning of smart grids
Why switch to smart grids
How it works
Challenges faced when using smart grids
Conclusion
What are smart grids ?
Smart grids are advanced electricity networks that use modern technology to improve the efficiency, reliability and sustainability of energy delivery
Benefits of smart grids
1. Smart grids are designed 2. Increase efficiency 3. Integration of renewable energy 4. Reduced carbon emissions5. Improved grid security
01
Class A design
class A design
Normal locked rotor torque and high locked rotor current. The rotor bars are quite large and sit close to the rotor surface. Low resistance (due to the large cross-section) and low dispersion reactance X2 (due to the position of the rod near the stator) Since R2 is small, the starting torque will be low. This design is the default motor design. Its relative efficiency is medium or high.
Applications: Typical applications such as drives for fans, blowers, centrifugal pumps and compressors, motor -generator sets and other machine tools where starting torque requirements are relatively low.
+ INFO
02
class b Design
class b design
At high slips (starting conditions) the reactances are large compared to the resistances in the rotor bars, so all the current is forced to flow in the low-reactance part of the bar near the stator. Since the effective cross-section is lower, the rotor resistance is higher. Thus, the starting torque is relatively higher and the starting current is relatively lower than in a class A design (about 25% less)
NEMA design B motor is the most common three-phase AC induction motor design. They have largely replaced design class A in new installations.
NAt the upper part of a deep rotor bar, the current flowing is tightly coupled to the stator, and hence the leakage inductance is small in this region. Deeper in the bar, the leakage inductance is higher
Pull-out Torque greater than or equal to 200% of the rated load torque
At low slips, the rotor's frequency is very small, and the reactances of all the parallel paths are small compared to their resistances. The impedances of all parts of the bar are approximately equal, so current flows through all the parts of the bar equally. The resulting large cross-sectional area makes the rotor resistance quite small, resulting in efficiency at low slips
+ INFO
03
class c Design
class C design
It contains double-cage rotor. At starting conditions, only the small bars are effective, and the rotor resistance is high. Hence, high starting torque. Used in high starting torque loads such as loaded pumps, compressors, and conveyors.
+ INFO
04
class d Design
class D design
D motors have similar torques to C motors, except that the Break Down Torque can reach up to 275%. They also have a much higher Slip, ranging from 5-8% instead of 1-5%. This creates a stronger torque, but makes the motors very inefficient. They are used for machinery with high peak loads such as elevators, hoists, and punch presses.
+ INFO
05
class E&f Design
class e & f
This is the newest NEMA design category Class E and Class F are already discontinued They are low starting torque machines
These called soft-start induction motors
These are also distinguished by having very low starting currents & used for starting-torque loads in situations where starting current were a problem
THANK YOU
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Transcript
Smart Grids
Presented to : Dr. Madeha Mohamed
Made by:
index
The meaning of smart grids
Why switch to smart grids
How it works
Challenges faced when using smart grids
Conclusion
What are smart grids ?
Smart grids are advanced electricity networks that use modern technology to improve the efficiency, reliability and sustainability of energy delivery
Benefits of smart grids
1. Smart grids are designed 2. Increase efficiency 3. Integration of renewable energy 4. Reduced carbon emissions5. Improved grid security
01
Class A design
class A design
Normal locked rotor torque and high locked rotor current. The rotor bars are quite large and sit close to the rotor surface. Low resistance (due to the large cross-section) and low dispersion reactance X2 (due to the position of the rod near the stator) Since R2 is small, the starting torque will be low. This design is the default motor design. Its relative efficiency is medium or high. Applications: Typical applications such as drives for fans, blowers, centrifugal pumps and compressors, motor -generator sets and other machine tools where starting torque requirements are relatively low.
+ INFO
02
class b Design
class b design
At high slips (starting conditions) the reactances are large compared to the resistances in the rotor bars, so all the current is forced to flow in the low-reactance part of the bar near the stator. Since the effective cross-section is lower, the rotor resistance is higher. Thus, the starting torque is relatively higher and the starting current is relatively lower than in a class A design (about 25% less)
NEMA design B motor is the most common three-phase AC induction motor design. They have largely replaced design class A in new installations.
NAt the upper part of a deep rotor bar, the current flowing is tightly coupled to the stator, and hence the leakage inductance is small in this region. Deeper in the bar, the leakage inductance is higher
Pull-out Torque greater than or equal to 200% of the rated load torque
At low slips, the rotor's frequency is very small, and the reactances of all the parallel paths are small compared to their resistances. The impedances of all parts of the bar are approximately equal, so current flows through all the parts of the bar equally. The resulting large cross-sectional area makes the rotor resistance quite small, resulting in efficiency at low slips
+ INFO
03
class c Design
class C design
It contains double-cage rotor. At starting conditions, only the small bars are effective, and the rotor resistance is high. Hence, high starting torque. Used in high starting torque loads such as loaded pumps, compressors, and conveyors.
+ INFO
04
class d Design
class D design
D motors have similar torques to C motors, except that the Break Down Torque can reach up to 275%. They also have a much higher Slip, ranging from 5-8% instead of 1-5%. This creates a stronger torque, but makes the motors very inefficient. They are used for machinery with high peak loads such as elevators, hoists, and punch presses.
+ INFO
05
class E&f Design
class e & f
This is the newest NEMA design category Class E and Class F are already discontinued They are low starting torque machines These called soft-start induction motors These are also distinguished by having very low starting currents & used for starting-torque loads in situations where starting current were a problem
THANK YOU