1. Advantages of vvvf drives over non vvvf drives for EOT cranes?
1.smooth start and stop.
2.no jerking of load.
3.exact posiitoning
4.better protection for motor.
5.high/low speed selection.
6.reliability of break shoe.
7.programmable break control.
8.easy circutry
9.reduction in controls
0.increases motor life
2. What is the significance of vector grouping in Power Transformers?
Every power transformer has a vector group listed by its manufacturer. Fundamentally it tells you the information about how the windings are connected (delta or wye) and the phace difference betweent the current and voltage. EG. DYN means Delta primary, Wye Secondry and the current is at o clock reffered to the voltage.
3. Which type of A.C motor is used in the fan (ceiling fan, exhaust fan, padestal fan, bracket fan etc) which are find in the houses ?
Its Single Phase induction motor which mostly squirrel cage rotor and are capacitor start capacitor run.
4. Give two basic speed control scheme of DC shunt motor?
By using flux control method:in this method a rheostat is connected across the field winding to control the field current.so by changing the current the flux produced by the field winding can be changed, and since speed is inversely proportional to flux speed can be controlled .armature control method:in this method a rheostat is connected across armature winding by varying the resistance the value of resistive drop(IaRa)can be varied,and since speed is directly proportional to Eb-IaRa the speed can be controlled.
5. what is the principle of motor?
Whenever a current carrying conductor is placed in an magnetic field it produce turning or twisting movement is called as torque.
6. what is meant by armature reaction?
The effect of armature flu to main flux is called armature reaction. The armature flux may support main flux or opposes main flux.
7. Give two basic speed control scheme of DC shunt motor?
By using flux control method:in this method a rheostat is connected across the field winding to control the field current.so by changing the current the flux produced by the field winding can be changed, and since speed is inversely proportional to flux speed can be controlled .armature control method:in this method a rheostat is connected across armature wdg.by varying the resistance the value of resistive drop(IaRa)can be varied,and since speed is directly proportional to Eb-IaRa the speed can be controlled.
8. what is the difference between synchronous generator & asynchronous generator?
In simple, synchronous generator supply's both active and reactive power but asynchronous generator(induction generator) supply's only active power and observe reactive power for magnetizing.This type of generators are used in windmills.
9. What is the Polarization index value ? (pi value)and simple definition of polarization index ?
Its ratio between insulation resistance(IR)i.e meggar value for 0min to insulation resistance for min. It ranges from 5-7 for new motors & normally for motor to be in good condition it should be Greater than .5 .
10. Why syn. generators are used for the production of electricity?
synchronous machines have capability to work on different power factor(or say different imaginary power varying the field emf. Hence syn. generators r used for the production of electricity.
1.smooth start and stop.
2.no jerking of load.
3.exact posiitoning
4.better protection for motor.
5.high/low speed selection.
6.reliability of break shoe.
7.programmable break control.
8.easy circutry
9.reduction in controls
0.increases motor life
2. What is the significance of vector grouping in Power Transformers?
Every power transformer has a vector group listed by its manufacturer. Fundamentally it tells you the information about how the windings are connected (delta or wye) and the phace difference betweent the current and voltage. EG. DYN means Delta primary, Wye Secondry and the current is at o clock reffered to the voltage.
3. Which type of A.C motor is used in the fan (ceiling fan, exhaust fan, padestal fan, bracket fan etc) which are find in the houses ?
Its Single Phase induction motor which mostly squirrel cage rotor and are capacitor start capacitor run.
4. Give two basic speed control scheme of DC shunt motor?
By using flux control method:in this method a rheostat is connected across the field winding to control the field current.so by changing the current the flux produced by the field winding can be changed, and since speed is inversely proportional to flux speed can be controlled .armature control method:in this method a rheostat is connected across armature winding by varying the resistance the value of resistive drop(IaRa)can be varied,and since speed is directly proportional to Eb-IaRa the speed can be controlled.
5. what is the principle of motor?
Whenever a current carrying conductor is placed in an magnetic field it produce turning or twisting movement is called as torque.
6. what is meant by armature reaction?
The effect of armature flu to main flux is called armature reaction. The armature flux may support main flux or opposes main flux.
7. Give two basic speed control scheme of DC shunt motor?
By using flux control method:in this method a rheostat is connected across the field winding to control the field current.so by changing the current the flux produced by the field winding can be changed, and since speed is inversely proportional to flux speed can be controlled .armature control method:in this method a rheostat is connected across armature wdg.by varying the resistance the value of resistive drop(IaRa)can be varied,and since speed is directly proportional to Eb-IaRa the speed can be controlled.
8. what is the difference between synchronous generator & asynchronous generator?
In simple, synchronous generator supply's both active and reactive power but asynchronous generator(induction generator) supply's only active power and observe reactive power for magnetizing.This type of generators are used in windmills.
9. What is the Polarization index value ? (pi value)and simple definition of polarization index ?
Its ratio between insulation resistance(IR)i.e meggar value for 0min to insulation resistance for min. It ranges from 5-7 for new motors & normally for motor to be in good condition it should be Greater than .5 .
10. Why syn. generators are used for the production of electricity?
synchronous machines have capability to work on different power factor(or say different imaginary power varying the field emf. Hence syn. generators r used for the production of electricity.
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