why the efficiency of the dc machine is high ,when it is
operated as a generator?
Answers were Sorted based on User's Feedback
Answer / guest
Effiiency of any machine is defined as the ratio of output
to the output.
Efficiency=(O/P)/(I/P)
MATHEMATICAL PROOF
Since electrical quantities are easier to measure in
comparison to mechanical quantities.
So in the determination of efficiency of DC machines,
we first find electrical quantities(input or output)and
subsequently find mechanical quantities(output or input)by
subtracting or adding the losses.
Efficiency of Generator=Output/input=(V*I)/(V*I+loss)
Efficiency of Motor = Output/input=(V*I-loss)/(V*I)
As long as machine is same, the rating and losses are not
going to change.
Clearly the ratio of above two equation is greater than 1
meaning there by efficiency of generator is greater than
motor.
PHYSICAL CIRCUIT PROOF
If we look into the circuit model,In case of generator back
emf causes less amount of current to flow through the
armature.So electrical losses(Cu loss) are less.Electrical
losses are function of current
In case of motor counter torque is produced so speed of
motor is less.So rotatinal loss(Core and friction) is
less.Rotational losses are function of speed.
Since loss:electrical loss > Mechanical loss.
So efficiency:Generator > Motor
Author:arbelectbit@yahoo.com
| Is This Answer Correct ? | 3 Yes | 0 No |
Answer / iamdon
Sorry for typing mistake....
Please read LAST WORD of first line as INPUT insted of
output.
Author:arbelectbit@yahoo.com
| Is This Answer Correct ? | 2 Yes | 0 No |
Answer / simon
Genrator can become motor but a motor cannot become Gen.
| Is This Answer Correct ? | 0 Yes | 0 No |
DG cranking voltage?
How to test Power Transfomer vector group in the field?
why transformer capacity is called KVA and motor capacity is called HP/KW? Why transformer capacity cant call HP/KVA?
Do you know how to maintain a generator, if so what are those maintenances?
where was current transformer protection units used and why??
What is Negative Potential Bias
how does the switching of capacitors in a capacitor bank take place when we use them at the load side to reduce the power factor?
HOW TO CALCULATE AMPs OF CURRENT TRANSFORMER IN HT Panel
Whatis the current capacity of 33KV/ 0.433KV transformer on Primary and secondary side/
While testing the value of the resistance for the earthing rod, two auxillary rods are connected to the earthing tester.What is the working function of a earth tester?
1.Why we use choke?If we use for high starting voltage then different type choke gives different voltage. Is it correct?
how braking & making capacity of circuit breaker is calculated?
Civil Engineering (5086)
Mechanical Engineering (4456)
Electrical Engineering (16639)
Electronics Communications (3918)
Chemical Engineering (1095)
Aeronautical Engineering (239)
Bio Engineering (96)
Metallurgy (361)
Industrial Engineering (259)
Instrumentation (3014)
Automobile Engineering (332)
Mechatronics Engineering (97)
Marine Engineering (124)
Power Plant Engineering (172)
Textile Engineering (575)
Production Engineering (25)
Satellite Systems Engineering (106)
Engineering AllOther (1379)