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Direct Current for Transformer
What happens when a transformer is supplied with direct current?
pmazulfi
- Oct 22nd, 2009
If DC supply is given to transformer there will be no change in the flux with time so there is no emf induced in the primary and secondary windings and hence transformer action will not take place.
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Form Factor
What is the link between Voltage and Form Factor?
lynxrat
- Dec 13th, 2009
Voltage is an electrical field, form factor is the actual size and shape of a device or piece of hardware.
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Run DC machine as a Generator
It is possible to run one DC machine as a generator or motor purposely? What adjustment we have to do for that operation?
ravs42
- Aug 21st, 2010
DC generators has got some limitations. The machine speed and output cannot be increased above certain limit due to commutation problems and cost. Besides using an alternator along with a rectifier circuit can be the best option to generate DC supply.
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Alternator capacity
Is it possible to increase the capacity of a synchronous generator upto 30% to 50% just to modify the cooling system but the other component remain same? Explain
Raman Jain
- Dec 3rd, 2009
Yes , one can increase the capacity by efficient cooling. This may be possible by modification in design , using better coolent etc.
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Transformer
What happens to the power factor of a transformer when the input voltage exceeds the rated voltage? Will it increase or decrease? Give explanation.
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Stray Capacitance
What is Stray Capacitance?
sreekanth_vigrahala
- Dec 24th, 2009
Stray capacitance is the imaginary capacitance which is exists between the winding turns.
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Open Rotor Conductors
What happens with squirrel induction machines if the ends of rotor conductors are kept open?
anilsabaji
- Jan 8th, 2010
If the end of the Rotor Bars are not connected then there is no current in rotor Bars and hence no torque will be developped. The moroe may however run at a very low speed due to eddy currents in the rotor.
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22 KV Cables
What are the maximum number of joints you can make in a (3x300mm, 22KV) cable over +/- 610m?
anilsabaji
- Jan 8th, 2010
There are no such rules. In some cases Cable Joints are strictly not allowed (in ships carrying Gas). Practically, as long as the joint does not increase the resistance of the cable than if it is not having any joint, it is acceptable for general industrial applications.
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Cable Selection
What is the max current rating for a 4 core * 1mm^2 cable?
anilsabaji
- Jan 8th, 2010
It varies depending on the material and the Temperature rating of the cable. You can safely use it for 5-7 Amps though the maximum rating can be up to 12Amp.
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Find Fault in Underground Cable
How to find out cable fault in a long underground cable?
napster.zatac
- Jan 23rd, 2010
Sectionalizing: it is risky and reduces cable reliability, because it depends on physically cutting and splicing the cable. Dividing the cable into successively smaller sections will enable you to na...
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Variable and Core Losses
Why copper is called variable loss & core loss is constant loss?
SURAJTHEGREAT
- Feb 22nd, 2010
Iron loss-When an electric current flows through a copper conductor (or any conductor), some energy is converted to heat. i(square)*r...this equation is obvious that iron loss depends on flowing curre...
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Earthing Cable Size
Calculate the size of earthing conductor between earth pit & 2000 KVA generator.
Lokesh M
- Jan 3rd, 2013
Earth Grounding Conductor (EGC) size should not be less than 25 percent of the capacity of the phase conductors or the over-current device. For rating or setting of automatic overcurrent device not ex...
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Power Between Source and Load
When eletricity is not used what happens to power between source and load?
pradipsabar2009
- Jul 30th, 2010
The power generated by source quickly responds to the load. If the load is suddenly disconnected, there will be only line load present so source cannot quickly change itself as a result heavy transien...
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Transformer Core Loss
What is core loss in a transformer?
veerateja
- Jun 16th, 2010
Eddycurrent and hysteresis losses are two core losses in transformers. Eddy currents are minimised by laminating the core where as hysteresis losses are minimised by using pure silicon steel. The two losses are similar in all rotating electrical machinery.
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Inductive Loads
Why does inductive loads consume KVARs?
sinhasunilk
- Jul 3rd, 2010
Electrical load is of three types: Inductive load, Resistive load and Capacitive load.The power drawn in a circuit will depend on type of load, the power is supplied. The circuit which has i...
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AC line Power Loss
High voltage is traded off for lower current in an AC line transmission. High current would require thicker cables, hence losses. How much can the voltage be increased to have a lower power loss? What is the ratio b/w current and voltage (p = I^2 * R).
Jayrod
- Jun 21st, 2010
"High current would require thicker cables, hence losses." - I disagree. The larger the cross-sectional area of a cable, the lesser the resistance (remember the formula for resistivity). Thi...
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Phase Advancer
Explain What is Phase Advancer?
mallick.subratkumar
- Apr 8th, 2010
It is like an power factor improvement deviceIt maintains the phase sequence of the linelike lag-lead compensator.
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Neutral Circuit and Core Balance Circuit Protection
What is the difference between neutral circuit and core balance circuit protection?
Raman Jain
- Nov 25th, 2011
In neutral circuit protection , the CT is placed in neutral conductor and it is true earth fault protection.
on the other hand , in core balance protection the CT is placed in 3-phase cable and measured the unbalanced current in the cable. So it is protection against the unbalance between phases. -
Vibro Motor Direction of Rotation
Two electrically operated Vibro Motors are fixed in parallel direction in vibrating feeder. What is the direction of both Vibro Motors?
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