0
Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
The voltage and frequency ARE the output of the generator. If you change the fuel to the generator, it will change speed, and the voltage will change. Less fuel = less speed = lower frequency = lower voltage.
How many amps can a 250 va transformer carry?
A transformer is a power source.
It will provide voltage to a device.
Find the voltage rating on the device, say 24V.
250/24 = ~10A.
How do you power a whole house with one generator?
Use a generator with a high enough rating to power the house, of course. Trying to power a house that draws 60A of current with a 10A generator is just never going to work.
What are the effects of metal impurities in iron?
Metal impurities can have many different effects on iron. Some of these effects may include, but are not limited to differences in strength, chemical inertness, and flexibility.
How do find voltage from mvar and mw?
mw is the unit of real power and mvar is unit of reactive power. You should now the current and power factor angle to calculate the voltage.
p=vi cos pi
q=vi sin pi
AnswerI think you mean MW, not mw -capital 'M' mega; lower-case 'm' milli!!! And the symbol for watt is a capital 'W', not a lower case 'w'. Also, I think you mean 'Mvar'(mega, not milli!).
What are the factors affecting the stability of a Q-point?
(1) current amplification factor due to change in temperature.
(2) collector current because of variation in leakage current.
Why is a capacitor connected in series with starter winding?
In single phase motors, there are two windings.
1)Main winding
2) starter (auxiliary) winding.
As per the double revolving theory in 1 phase machines, motor can rotate if current in the starter winding have near to 90 deg. phase shift wrt main winding.
Now current flowing through capacitor leads by 90 deg. Ideally. So this is how we can get two currents which are having phase shift wrt each other. And the machine can rotate.
Is an AC generator can use AC motor and vice verso?
Are you planning to build a perpetual motion machine in which the power generated by an AC generator is used to run an AC motor which is used to run the same AC generator which provides it with power? Because that won't work. Yes, you can use a motor to generate electricity, and you can use electricity to run a motor, but the process is not 100% efficient and if you try to make it a closed loop, it will run down fairly quickly. So, what do we actually do? We use fuel to run an AC generator, or we use waterfalls or wind, or some other energy source, and then we use the power to run our motor.
How long does it take 10C to flow past a point if the current is 5A?
curent= couloumb/ time
5=10c/t
t =10c/5a
t =2sec
A definite time over-current relay operates like an instantaneous over-current relay coupled with a timer. Once current reaches the pick-up value, it initiates the timing circuit. As long as current stays above this pick-up value, the timer will continue to time. Once the definite time setting is reached, the relay gives trip signal to the circuit breaker.
What is the voltage tolerance of a standard electric motor?
the voltage tolerance of a standard electric motor is
When a load on a normally excited synchronous motor is increased its power factor tends to?
power factor normally goes to the lagging
What is the name of an instrument used to vary electrical resistance?
Rheostat is the name of an instrument used to vary electrical resistance.
Why to use buchholz relay in hermatically sealed transformer?
Buchholz relays are used with oil-filled transformers, and these types of transformerare not normally hermetically sealed, because the oil must be allowed to expand and contract with changes in temperature, and must be able to displace air within the tank. Air vents are provided for any resulting air displacement, and are normally fitted with silica-gel chambers to ensure any air entering the transformer when the oil contracts is dry.
Buchholz relays are normally fitted in an inclined pipe between the main tank of the transformer and an elevated expansion tank, so that any gases formed within the tank pass up that tube and are collected within the Buchholz relay's chamber. A Buchholz relay is designed to set off an alarm in the event of a loss of oil or an excessive collection of gas within the relay; a further fall in oil level, or a catastrophic explosion within the tank, will cause the Buchholz relay to disconnect the transformer.
What should be the minimum insulation value of a 20 kw 415v phase motor?
415V
commonly available wire is 300V or 600V
so that would need to be 600V wire
to use a megger or a hipot tester
(2* operating voltage +1000V)
2000 volt megger or hipot should verify the wiring in this instance
2500v megger will be necessary for 600V wire and wiring devices
you also must look and ambient temperature and humidity
a test after some operation time can verify this
What is the relationship between total resistance and the resistance across each load?
There is no such thing as 'resistance across' a load! The correct term is 'resistance of a load'.
To answer your question, it depends on how the loads are connected. If they are connected in series, for example, the total resistance is equal to the sum of the individual resistances. If they are connected in parallel, then you must use the following equation: 1/R = 1/R1 + 1/R2 + 1/R3 + etc.
For any other connection, you will have to work it out individually.
How wattmeter is connected in circuit?
A wattmeter has two coils: a current coil and a voltage coil. The current coil is connected in series with the load, while the voltage coil is connected in parallel with the load (just in the same way an ammeter and a voltmeter are connected). The wattmeter's polarity markings must be observed while making these connections -if the wattmeter reads 'downscale' (backwards), then the connection to either one (but not both) of the coils must be reversed.
What is resin impregnation process?
In resin impregnation, any porous material is made impervious by filling its pores with the resin.
What is power factor of an R L series circuit?
Power factor in any circuit is the ratio of the load's true power to its apparent power. It's also the cosine of the phase angle. In L-R circuits, it's described as a 'lagging power factor', because the load current lags the supply voltage.
Steel is not used as an electrical conductor because, although it is a conductor, it's not a very good conductor -as is copper and aluminium, for example. A steel-wire core is used, however, to reinforce aluminium conductors on transmission tower lines
