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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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Phase Usage
Why and when we use single phase and three phase?
raviiisc
- Oct 31st, 2010
This is the most common question.Whenever we are dealing with large quantity of power we use the Three phase system rather than the single phase system. The cause is the cost of eqipment is more....
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Inverter and UPS
What is the difference between INVERTER and UPS?
prafulla patil
- Oct 29th, 2010
The main difference between Inverter and UPS is switching time.Inverter switching time is inverter switching time is more than UPS , inverter Takes approx 500 millisecond to switch , that’s why ...
full61
- Apr 15th, 2010
Inverter converts only DC to AC but UPS converts AC to DC and then store it after that it convert DC to AC.
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Cable fault identification.
One 3.5C cable is connected in a feeder with the neutral is isolated in the two ends(3 phases connected and neutral open in both sides). Now on rear end the output voltage is getting reduced by 20V in two phases and 40v increased by another phase.(between phase and neutral but neutral in open in two ends).the cable is meggered and we got the value of 100Mega ohm. There is no load in rear end. Kindly...
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Induction Motor
In single phase induction motor, what is phase? what is induction? Why only this motor used in fans?
guntur.srikanth
- Sep 30th, 2010
Mainly the induction motor works with mutual induction principle that is why we are using them in fans
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Quality Factor
What is the importance of quality factor in resonance?
thakur.rajesh.ranjan
- Sep 27th, 2010
Sinusoidally driven resonators having high quality factor resonates with greater amplitudes but have a smaller range of frequencies around that frequency for which they resonates. Thus a high Q (quali...
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Water Level Sensor
What sensor is used to measure the level of water in a tank?
thakur.rajesh.ranjan
- Sep 25th, 2010
A small rubber ball, we generally use in our dewatering sump for water level sensor. This gives command mechanically to level switch.
ravs42
- Aug 6th, 2010
A simple mechanical model for water level indicator includes a float(rubber ball) providing? a mechanical link to the indicator i.e. d output. When the water level rises the float due to it's light weight raises up and via the link the pointer will move to display the required output.
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Reactive Power
What is mean by reactive power? How it is generated?
Sreebai
- Sep 21st, 2010
Reactive power is the power required to transmit the active power. The reactive power is like an envelop,that is used to send a letter. Without this we cant send the active power and it cant be too hi...
SURAJTHEGREAT
- Mar 3rd, 2009
We know reactance (hypothetical resistance) which reduce the supply voltage by opposite flowing induced emf. This power loss due to reactance is known as reactive power. This power is not useful power. It is a waste. However it is useful in determining the phase angle.
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Synronizing Degree
In which degree synronizing has to be done in a 3 phase alternator?
mgbushan
- Aug 24th, 2010
When you have to synchronize the alternator with the reference bus, then The voltage, Phase angle, frequency difference of the alternator with refernce to the bus reaches within the tolerable set...
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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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Transformer Taping
Why tapings of Transformer is always provided on HT side? why not on LT side?
ravs42
- Aug 21st, 2010
It is because of two reasons1.high voltage regulation.Large range of voltage can be obtained.2.less current value on the HV side,as a result,no sparking problem.
Raman Jain
- Dec 3rd, 2009
Tapings in transformers are provided at HV side . The reasons are : 1. Less current has to be handled .2. As the LV windind is wounded first i.e near the core and HT winding is wounded on the top of the LV winding. So it is easier to provide Taps on HV side.
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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.
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Spark Plug
When the power supply cable got sparked, it gets burnt or caches fire then explain why the spark plug in our automobiles never get burnt or catch fire even it spark's?
ravs42
- Aug 6th, 2010
Generally in automobiles we have an alternator that produces ample AC supply that is converted to 12V DC supply via the help of rectifiers and regulated IC usage. The 12V is then feed to the batterri...
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Electrical Machine Harmonics
What is harmonics and how they are produce in electrical machine?
ravs42
- Aug 6th, 2010
Harmonics are the integral multiples of the fundamental values of current/voltage quantities. Generally it is caused due to non linearity caused by the load which adversely affects the supply side. Main impacts occurs in capacitors, telecommunication lines, power transformers, etc.
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Quality Factor in Resonance
What is the importance of quality factor in resonance?
sujit.185
- Aug 5th, 2010
QUALITY FACTOR actually signifies the voltage gain or voltage amplification factor of a given ckt.
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Bulb Power
The bulb has a rating of 500W for 220V, if the voltage is 110V, What is the power of the Bulb?
mohit parashar
- Jul 28th, 2010
Given:p=500WV=220VP=VII=2.27Athan by ohm's lawV=IRso R=96.91Ohm which is constant.if V=110Vthan I become 1.135AsoP=VIP=125W.
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Fault Detection in Underground Cables
If there are three underground cables if a fault takes place in one of them, How will you detect it?
pradipsabar2009
- Jul 28th, 2010
Measure the resistance of each cable between farther ends, if there is a considerable variation in any one of the cable, that is the faulty one. This method is also used in industries called as "Insulation Resistance Test".
dhands
- Jun 6th, 2010
1. Check phase to pase insulation resistance value and phase to earth insulation resistance value.
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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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Voltage Levels
Why all voltage level are multiples of 11, like 220V, 440V, 1100V instead of 200V, 400V, 1000V?
pradipsabar2009
- Jul 30th, 2010
The value of form factor is 1.1 which is calculated for the sine wave. At this value of form factor, leakage flux is minimum and efficiency is maximum for any electrical machines. These machines are operated at sine waves.
dhrumil041189
- Jun 11th, 2010
Because number of disc of insulators are rated in order of 11 kV so all these are transmitted in the multiple of 11.
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Convert Single Phase to 3 Phase
How to convert a single phase supply to a 3 phase balanced supply?
raviiisc
- Jul 14th, 2010
The are two methods.1. First convert 1-ph AC into DC by using converter, then that DC is converted to AC by using the power electronic circuit named as three phase inverter using any modulation t...
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