-
Transformers and Varying DC Current
Will DC current that varies, for example a DC square wave, but that only sinks to neutral (0V) and not enough to cause current to flow in the opposite direction, pass through a transformer? If so, how will you be able to calculate reactance for this?
ravs42
- Aug 8th, 2010
A DC square wave will have a very high value of dv/dt as compared to the pure sine wave. When it is striked to transformer, a high value of dv/dt would not be responded by it, as a result, the waves ...
Abhijit_atrangi
- Feb 22nd, 2010
No, only change in flux will induce the emf in a ckt. and that only feasible with AC that goes in opposite direction also. But in case of DC that produce flux with no change that never cause any emf in circuit. In case of DC square wave you change the magnitude of a wave from zero to max.
-
SC Test
Why SC test is performed on LV side?
-
Location of LA (Ligtining arrestor)
Where do we locate lightining arrestor in transmission line?
anupam_srivastav
- Jan 9th, 2010
Ligthing arrestor is mounted on the starting of S/s as well as near T/f for the protection of equipment. Lightining arrestor has nothing to do with lightining it is mounted there from protection from lightining surge. Ci cover & lightining Mast is used for Lightining Attack.
ashok.bhaarath
- Dec 10th, 2009
Ligtining arrestor is placed in Starting of the Substation because of avoiding the over currents &voltages
-
Universal Motor
What is universal motor?
-
Series Shunt Motor
Can we recognise if motor is series or shunt by visual inspection? If yes how?
Abhijit_atrangi
- Sep 1st, 2008
Yes, we can in the lab, theire is a winding denotes on the machine panel where it is the series or shunt motor, where series motor having less no. of turns of field in seies with armature and shunt has more no. of turns of field in shunt with armature.
-
D.C Motor Rheostat
If the position of rheostat is changed from minimum position to maximum position in D.C shunt motors speed is increased, how?
Abhijit_atrangi
- Aug 19th, 2008
In D.C shunt machine by inserting the rheostat in the field we can increase the speed above the base speed in the ratio 3:1 but above that machine get overheated. When we increase the resistance field...
-
Transmission Line
What is Transmission Line? How it is used? Give examples.
Abhijit_atrangi
- Aug 19th, 2008
Line which is used to trasmit the high voltage or high power is called transmission line, high voltage E.g. 220kv, 132kv, 66kv etc. all this voltage are of transmission voltage range. Example of transmission line is : D.C line of +/- 800kv from Chandrapur to Padage in India
-
Alternator and Generator
What is the diffrence between Altrnator & Generator? Outline its working principal.
-
Cable selection
Why Cable selection depends on Load current? (UG Cables & OH lines)
soumendasbiswas
- Apr 26th, 2012
Cable selection not only depends on the load current but also depends on Temperature, Length (Distance between LT Switchgear MCC/PMCC to Motor). If load is increase then current will also increase if ...
raju
- Apr 6th, 2012
Voltage is directly proportional length, current is proportional to area of cross section of the wire.
-
Fuse Rating
Dear AllI wan to know that we are using large type of cable like 300sqmm and other and our load also in much kw but we are using a small type fuse in main supply (not HT Side) how can it bear load.
Abhijit_atrangi
- Aug 7th, 2008
Fuse rating and cabel selection is depend upon the load current and fuse current is always greater than the load current. Suppose your load is motor then the starting current of motor is 3 times gre...
-
Why is the transformer rated in KVA?
Read Best Answer
Editorial / Best Answer
Answered by: NagaseshaReddy.M
- Sep 10th, 2007
kVA is the unit for apparent power. Apparent power consists of active and reactive power. Active power is the share of the apparent power which transmits energy from the source (generator) to the user. Reactive power is the share of the apparent power which represents a useless oscillation of energy from the source to the user and back again.
It occurs when on account of some »inertia« in the system there is a phase shift between voltage and current. This means that the current does not change polarity synchronous with the voltage. But the heat generated in a winding as well as the eddy current losses generated in a transformer core depend on the current only, regardless of whether it aligns with the voltage or not.
Therefore the heat is always proportional to the square of the current amplitude, irrespective of the phase angle (the shift between voltage and current). So a transformer has to be rated (and selected) by apparent power.Raghu
- Feb 9th, 2018
In transformer there is two losses
1. Iron loss
2. Copper loss
The iron loss is depands on Voltage
And the Copper loss is depands on current.Umar Naik
- Nov 26th, 2017
There are cu losses and iron losses which are not dependent on power factor thats why we rated it in KVA.
-
When there is a sudden loss in the demand what happens to the transformer and generation?
Read Best Answer
Editorial / Best Answer
csbalu- Member Since Aug-2009 | Aug 29th, 2009
When there is a sudden loss of load, The Generator terminal voltage increases due to the fact that the IX drop in the generator winding decreases. The EMF generated being the same the reduced reactance loss leads to a sudden rise in generator voltage..but the AVR (Automatic Voltage Regulator) will act instantly to bring this voltage to the set value by reducing the excitation.
There is practically no effect of this on the transformer barring the reduction in I2R (copper Losses) and reduced IX drop.csbalu
- Aug 29th, 2009
When there is a sudden loss of load, The Generator terminal voltage increases due to the fact that the IX drop in the generator winding decreases. The EMF generated being the same the reduced reactanc...
spcspc1654
- Jul 19th, 2009
When there is a sudden loss in the demand then there is over-excitation of the generation and the power factor is increased. Also the rotor angle of generator is changed (unstable) for a while.
