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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
Can DC series motor work on ac and DC and why?
A dc series motor can work on dc and ac because dc motors are totally reversible.
How tertiary winding of power transformer acts as stabilizing winding?
in star-star neutral transformer at unbalanced load condition zerosequnce current will be flows in secondary side but this current can not be balanced by primary side because its not having neutral to circulate zerosequence current.due to this unbalance voltage will appeared in primary side but the tertiary delta winding allows circulate the zerosequence current so the primary voltage will get stabilized.
What is the difference between EMF and terminal PD?
An electromotive force is the potential differenceappearing across the terminals of a battery, generator, etc., when that device is not supplying any load. When the device is supplying a load current, the electromotive force is equal to the sum of the voltage drops around the complete circuit, including any internal voltage drop.
A potential difference (also known as a 'voltage'), as the name implies, is the difference in potential between two points.
A terminal potential difference is the potential difference appearing across the terminals of a voltage source, such as a battery or a generator, which varies according to the load supplied.
When the battery or generator is off load (i.e. no load is connected to it), the terminal potential difference is equal to the electromotive force of that battery or generator.
The terminal potential difference tends to decrease as the load current increases, due to a corresponding increase in the internal voltage drop of the battery or generator.
R for resistor, C for capacitor.
RC circuit is a circuit built with a resistor and a capacitor.
This circuit will have a typical pulse response that looks like exponential decaying and a typical resonance frequency.
How much power in a 15000 kva transformer?
The power in a 15 MVA (15000 KVA) transformer depends on the power factor. You did not specify the power factor, so I will assume a power factor of 0.92. Simply multiply MVA by PF and you get 13.8 MW.
What is an example of self-inductance?
self induction occurs in an Inductor itself. Self induction happens because of the flux change in the circuit due to varying current of the same circuit and not the current change of some other circuit thats why the term "self" is used
Engr. Saif Ali Solangi
What is the difference between 1sec and 3sec duration of short-circuit withstand capacity?
The difference between 1 second and 3 seconds is 2 seconds. In terms of short-circuit withstand capacity, it can mean the difference between no damage and damage occurring to the equipment and wiring. Heat rises extremely fast in a short-circuit situation, and you want your protective device to trip before damage is done.
What are the harmful effects of short-circuit fault on the power system?
A short circuit causes large amounts of power to flow. If left uninterrupted for long enough, this could cause system instability, and eventual collapse of the power grid (wide area blackouts).
Why A synchronous motor is sometimes called a synchronous capacitor Explain?
A synchronous motor can operate as either a Generator or a Motor.
When a synchronous motor has current applied to the windings on its rotor and the stator is energized with say a 50hz line supply (with little or no physical load) then the exact amount of excitation provided by the rotor can determine whether the stator displays inductive or capacitive properties.
If the rotor is under excited (too Little rotor current) the Synchronous Motor will behave as an Inductor, however if the rotor is over excited then the Synchronous Motor will behave like a Capacitor.
Hope this helps
What will happen if winding resistances of a motor are different?
The motor will pull different amounts of power on the different phases, which will result in not operating smoothly for three phase motors.
What is the no load current of 1600 kva transformer?
No load current depends on the design of the transformer, and what voltage it is energized at. It will typically be below 1% of full load, and can be significantly below 1% for utility sized transformers.
What is the load for the doorbell circuit?
The typical doorbell transformer is capable of about 1 ampere .... so depending on your bell or whatever it rings , the load will be less. Some electronic bells can be very low energy devices so 100-200 milliamps ).1 to 0.2 amperes) might be more in their operating range.
What is helical winding in transformer?
Helical winding is helically wound around the cylindrical generatrix leaving a duct gap of 4.5-6 mm wide between two adjacent turns around the height.
A turn of helical winding consists of several parallel rectangular conductors flat-wise and close to each other in the radial direction of the winding.
For uniform distribution of current between the parallel branches, transposition of conductors is used.
In the above diagram the transposition of helical winding turns in 3 places along the height: in the middle- the so called middle transposition (a) and the two group transposition (b),(c) are made so that the winding is divided along its height in approximately equal parts.
the no. of parallel conductors in one turn of a helical winding usually varies from 6-20. The helical winding is widely used in low voltage transformers of medium and especially of high voltage.
How do you measure 11kv voltage?
By electrostatic moving iron type voltmeter, you can measure upto about 200kV directly.
Answer">AnswerIn substations, high voltages, such as 11 kV, are measured using a relatively small step-down voltage transformer (UK terminology) or potential transformer (US terminology).
The secondary voltage of a voltage transformer is typically standardised at 110 V, which then matches the full-scale deflection of the voltmeter to which it is connected. So a typical transformation ration would be 11 kV/110 V, 33 kV/110 V, 132 kV/110 V, etc.
Voltage transformers, together with current transformers, are classified as 'instrument transformers', whose outputs are used for measurements or for driving protective relays. They also have the important function of being able to electrically isolate their secondary (measurement) circuit from their high-voltage primary circuit.
How you convert a power supply into 12v DC?
DC 12V power supply can convert 110/220V AC power source to 12V DC.
What is meant by switch gears in electrical engineering?
To protect the system from faults the equipment used is known as switch gear
AnswerSwitchgear is the generic name for transmission and distribution equipment designed control, disconnect, and protect an electrical system. Switchgear includes circuit breakers, fuses, and isolators (US term: disconnectors). As well as being used to control circuits by opening or closing those circuits, circuit breakers are designed to interruptand to close onto electrical faults so must incorporate means of extinguishing the arcing associated with such faults. Circuit breakers, therefore, have a essential role in responding to protection systems. Isolators are non-load breaking switches, designed to isolate equipment (including circuit breakers) from high voltages, so that the equipment can be maintained.
Why tilt is formed for square wave input in highpass filter?
Lets have an example of simple RC high pass filter. Here, we take output across Resistor(in HPF). The tilt is because of charging of capacitor. you can say, as capacitor charges (ofcourse with voltage) the same amount of voltage has to drop across resistor ( to follow KVL). Since we are taking output across Resistor, so we see small voltage drop (as tilt). This can be minimized by keeping RC time constant large.
The statement current is directly proportional to voltage and inversely proportional to resistance is known as Ohm's Law.
Why flooring of substation is done with stones?
Substations usually use crushed limestone in the ground design to help minimize GPR (ground potential rise) within the substation. Without getting too technical, it helps keep the step and touch potential within limits so people working in the substation aren't hurt.
it is the amount by which instrument's sensitivity varies as ambient conditions change.
What is the difference between directional and non directional over current protection?
The directional part. Directional relays will operate for events "in front of" them, but will not operate for events "behind" them. Typically directional relays are used in non radial situations such as on the bulk electric system. Non-directional overcurrents are commonly used on radial lines.
Why the alternator do not operate near the knee of its saturation curve?
Actually, alternators (synchronous generators in other parlance) are normally operated slightly saturated by design.
If they were operated completely unsaturated, the machine is not being used to its full capability.
We don't attempt to operate them beyond the knee, because the losses increase significantly, and the output voltage & current are distorted.
It is important to note that there are two different windings to consider when discussing saturation.
The DC field (rotor) winding is usually operated somewhat in the saturated region.
The AC armature (stator) winding is operated near - but below - the knee to avoid output distortion.
