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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
What is the use of sumpner's test in transformer?
this test helps in finding the core losses and copper losses in single test , it is also called as back to back test or heat run test .
B - Dynamic resistance
What is the hermetically sealed transformer?
Hermatically sealed transformer is a transformer design which has no conservator. Here the dielectric insulating fluid in the transformer tank is completely sealed and is in zero contact to the atmosphere.
This type of transformer is used in applications where the transformer is to be installed in harsh climatic conditions(smoke,pollution,dusty environment,etc) or user prefers low maintenance transformer. The design avoids air in the transformer tank therby avoiding sludging and oxidation of the dielectric fluid. Hence it would be safe to say that these transformers need no maintenance of the dielectric insulatating fluid(usually Oil).
Normally these type of transformers are accommodated by devices that measure heat related volume variations.
Gas cushion is used to compensate the volume variation due to heat. Normally the gas is nitrogen. This gas is thermally uncoupled from the dielectric liquid.
A constant KVA load is an electrical load which has a constant apparent power consumption regardless of small changes in voltage. Constant KVA loads in industry are typically electric motor loads such as induction motors.
The interesting thing about an induction motor and why it is called a constant KVA load is, for a constant level of torque output of the motor, if the terminal voltage decreases by say 5% the motor current will actually increase by about 5%. Note that this constant KVA effect will only occure withing an narrow range of voltage deviation.
This is the opposite of a static (constant Z) load which if the voltage decreases the current decreases.
What types of complications occur with peritoneovenous shunt insertion?
Complications following peritoneovenous shunt insertion are common and include infection, leakage of ascitic fluid, accumulation of abnormally large amounts of fluid in the intercellular tissue.
Why kirchhoff's voltage law is applicable for open circuit?
Kirchoff's Voltage Law does not work, per se, for open circuits. You need a closed circuit for it to make any kind of sense.
The signed sum of the voltage drops going around a series circuit is equal to zero.
That means you have a closed circuit.
However, it can be argued, correctly, that an open circuit is simply one that has two nodes with infinite resistance between them. Assuming that all of the other nodes have something less than infinite resistance between them, then Kirchoff's law does work, of sorts, in that the voltage drop across all nodes that are not voltage sources will be zero, because there is no current, and the voltage drop across the two nodes with infinite resistance will be equal to the sum of the voltage rises across the voltage sources. Current sources in such a circuit will not work, because, with zero current, they would attempt to generate infinite voltage.
AnswerKirchhoff's Voltage Law does indeed apply to an open circuit, because the voltage drop across the open part of the circuit is numerically equal to the supply voltage and, hence, the algebraic sum of the voltage drops around that particular loop is zero.
Kirchoff's Voltage Law does not work, per se, for open circuits. You need a closed circuit for it to make any kind of sense.
The signed sum of the voltage drops going around a series circuit is equal to zero.
That means you have a closed circuit.
However, it can be argued, correctly, that an open circuit is simply one that has two nodes with infinite resistance between them. Assuming that all of the other nodes have something less than infinite resistance between them, then Kirchoff's law does work, of sorts, in that the voltage drop across all nodes that are not voltage sources will be zero, because there is no current, and the voltage drop across the two nodes with infinite resistance will be equal to the sum of the voltage rises across the voltage sources. Current sources in such a circuit will not work, because, with zero current, they would attempt to generate infinite voltage.
Read more: http://wiki.answers.com/Why_kirchhoff's_voltage_law_is_applicable_for_open_circuit#ixzz1i2fWNqfN
What happen if the iron core is replaced by gold in the case of transformer?
You will have a very expensive but worthless transformer. Gold is not a ferromagnetic material, so it will not contain the magnetic flux needed to link the separate windings.
What are the uses of derivatives in electrical engineering?
When you are talking about field and line calculations, complex differential equations are sometimes the best way to represent electrical characteristics. current and voltage in AC applications is defined using differential equations. You may use derivatives in control system modelling. There are many others.
Why are the brushes of a dc machine always placed at the neutral points?
The function of brush is to collect current from rotating commutator and supplies the current to external stationary load.
The brushes of a DC machine are placed at neutral points because the current in the rotating part drops to zero at the neutral point.
If brushes are placed in location other than the neutral points, then the current may be switched off and it causes magnetic field and it may also create voltage spikes and arc at brushes.
This explanation was found on a OMRON newsletter:
Typically, a relay being tested for UL TV Rating sees an Inrush Load 10 times that of steady state current at 120VAC.
For example, a relay receiving TV-3 Rating sees approx. 30A Inrush for a very short duration at 120VAC and settles to a steady state current of 3A, 120VAC before cycling off. Relays must operate successfully for 25,000 cycles of TV Load Testing to receive a UL TV Rating.
What is the resistance of a torch bulb rated at 2.5 V and 500 mA?
well if the potential difference (voltage) that i apllied across the light bulb is exacty 2.5v (as it can vary due to the interal resistance of th batteris used) then you can use Resistance=Voltage/current (R=V/I) to calculatete resistance. Therefore since 500mA is equivlant to 0.5A R=2.5/0.5=5 ohms.
hopeully that is helpfull
Why the transfermer rating is in KVA where as generator rating is KW?
Transformers are rated based on the amount of current flowing through them, irrespective of whether the current is in phase with the voltage or not, thus KVA.
When it comes to generators, what the owner is interested in is how much real power the generator can deliver (watts). Most generators are rated at a specific real power and a power factor (often .95).
How many hours can you run a 300 amp load if you have a 300 amp hr battery bank?
A 300 ampere-hour battery can supply 300 amperes for somewhat less, sometimes substantially less, than one hour. It might not even be rated to provide 300 amperes at all. It depends on the battery.
The reason for this is that ampere-hour ratings are, by definition, normalized to an eight-hour rate. This means that you can pull 300/8, or 37.5 amperes from that battery for 8 hours. That is the reference point.
If you were, for instance, to pull 18.75 amperes, you would expect the battery to last somewhat longer than 16 hours, and if you pulled 75 amperes, you would expect the to last somewhat less than 4 hours, both from a full charge, and both from a recently equalized state.
You need to check the published discharge curve for the batter to know for sure.
What is the net resistance of two resistor connected in series?
The net resistance of two resistors connected in series is the sum of the two resistances.
RSERIES = Summation1toN RN
Why does the transformer on my microwave smoke?
If the transformr is inside the microwave, something could've shorted causing things to draw more current, more current makes more saturation of the iron core, causing the coils to burn. If this continues, IMMEDIATLY salvage the parts, as inverter microwaves are annoying and are a PAIN to repair. Also when you take the transformer out you can get 2000v easily but with inverters you need some company's trade secret frequencies. Hope this helped! Also transformer based microwaves are not exactly made anymore so keep the parts (All of them) as they will be HISTORY. Oh and if the microwave transformer is outside and you've hooked it up to 120 (Getting 2000v out) then what you're doing on the output is drawing too much current. MOT's (Microwave oven transformers) can only handle about 2A before overheating. In that case buy a ballast inbetween the mot and the 120v input. It will limit current draw from the mot to the wall preventing overcurrent. Hope this helped!
What is the effect of load factor and diversity factor on cost of generation in a power station?
Load factor effects the cost of generation. Higher the load factor higher will be the average load. So no. of units generated for a given period of time for the same max. demand will be more. Therefore, overall cost per unit of electrical energy decreases due to distribution of standing charges which are proportional to the max. demand and independent of units generated.
Diversity factor effects the cost of generation. More is the diversity lesser will be max. demand due to which installation capacity of plant will be less. Lesser is the installation capacity lesser will be the capital required for installation. So lesser will be generation cost. And the fixed charges in the tariff would be less.
What is the inductance of a 20 mH inductors connected in parallel with a 50mH inductor?
Lt= 1/(1/L1+1/L2)
Lt= 1/(1/.02+1/.05)
Lt= 14.29 mH
Is a sump pump an open loop system?
A typical sump pump just sits there and does nothing until a sensor detects that sufficient water is present to turn on. If it just pumped forever it would be open loop. The fact that it also senses when the water has been pumped and stops makes it a closed loop system.
If you're referring to the water in the system, it is an open loop system, since the water is not held in the system.
