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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
How do you find primary number of turns in a transformer?
Unfortunately, it is not practical to find the number of turns in a transformer's windings. However, what matters is its turns ratio. This can be done by applying a low AC voltage to the higher-voltage* winding, and measuring the resulting voltage appearing across the lower-voltage winding. The turns ratio will be approximately the same as the voltage ratio.
(*NOT THE OTHER WAY AROUND! Or you may up with a dangerously-high voltage induced into the higher-voltage winding!)
What happens when fuse is given to neutral?
A fuse should always be inserted into the line conductor, never the neutral conductor.
If a fuse has been inserted, inadvertently, into the neutral, an overload will still operate the fuse, but the line voltage will not be isolated from the circuit -thus presenting a shock hazard. Furthermore, it will not protect against an earth (ground) fault that occurs in the circuit.
Why copper loss is called variable loss?
Cu loss means I^2*R loss so it depends on R and I.If we make wire more resistive it means it will increase the value of R so copper loss will be increase.So to concentrate on wire size we can vary the R value and can protect the copper loss.So it is called variable loss.
What are equalizer rings used for?
An equalizer, or equalizer connection, connects two or more generators operating in parallel at a point where the armature and series-field leads join (see Fig. 7.13), thusconnecting the armatures in multiple and the series coils in multiple so that the load will
divide between the generators in proportion to their capacities. The arrangement of connections to a switchboard (Westinghouse Electric Corp.) is illustrated in Fig. 7.14.
Consider, for example, two overcompound-wound machines operating in parallel without
an equalizer. If for some reason there is a light increase in the speed of one machine, it will
take more than its share of load. The increased current flowing through its series field will
strengthen the magnetism, raise the voltage, and cause the machine to carry a still greater
amount until it carries the entire load. When equalizers are used, the current flowing through
each series coil is inversely proportional to the resistance of the series-coil circuit and is
independent of the load on any machine; consequently, an increase of voltage on one
machine builds up the voltage of the other at the same time, so that the first machine cannot
take all the load but will continue to share it in proper proportion with the other generators
What is the normal allowable source voltage deviation from the motors nameplate voltage rating?
It can be 10% min and 5% max.
AnswerA nameplate voltage is a 'nominal voltage', and manufacturers normally design their products for the allowable variation in nominal voltage of the country in which they are to be marketed. So, for those products intended for, say, the British market, manufacturers would take into account the British allowable variation, which is 230 V (+10%/-6%). And, no doubt, most manufacturers would widen this variation to allow a 'factor of safety' for their products.
Will the improvement of power factor will increase the efficiency?
Efficiency is defined as the ratio between the output power and the input power of a machine, expressed as a per unit or percentage.
Power factor improvement has absolutely no effect on the behaviour of a load. All it does is to reduce the magnitude of the load current. A reduction in load current means that less copper can be used in the supply of energy to the load. However, it doesn't effect either the output or input power of the load. So the answer is no, power factor has no effect on the efficiency of a load.
You could argue, however, that if improving the power factor of a load reduces the supply current, leading to lower line losses, then there is an improvement in the efficiency of the supply system.
Why is the scale of moving iron instrument non uniform?
A moving-iron instrument works on the principle of repulsion between the like magnetic poles (like poles repel) induced in two soft-iron pole pieces (one fixed, the other moving and deflecting the pointer), by the current flowing in a coil. This force of repulsion isn't linear -it reduces the further apart the pole pieces become, obeying what is known as the 'inverse square' law. So, the non-linear scale over which the pointer moves reflects the non-linearity of the force deflecting the pointer. The effect of this non-linearity can be reduced by carefully shaping the fixed pole piece so that the effective surface areas of the two pole pieces are modified as they move apart, partly compensating for the loss of linearity by the force, as they move further apart.
How do you test reverse power trip?
There is a test swich which will change the polarity of the sensors........
As you have written it (mvar), it stands for 'reactive millivolt amperes', but I think you probably mean 'Mvar', which stands for 'reactive megavolt amperes'. These are units for reactive power of an alternating-current load.
A lower-case 'm' represents 'milli', whereas an upper-case 'M' represents 'mega'. 'V' represents 'volts', 'A' represents 'amperes', and 'r' represents 'reactive'.
SI does not specify a symbol for reactive volt amperes (it only recognises 'watts'), so it is seen in written in various ways, including: var, VAR, VAr, VA(r), and VAr -in each case, it is also common to see a 'raised period' between the V and the A -e.g. V.Ar .
How many diodes in a transistor?
There are two semiconductor junctions. Transistors are designated as NPN or PNP and a diode is an NP or PN junction depending on direction of current flow. However, the function of a transistor is different than two back to back diodes.
Bridge Rectifier
What happen if 230V AC bulb is connected to 110 V DC?
A lamp will only operate at its rated power at its rated voltage. So if you connected a 230-V lamp to a 110-V supply, its brightness would be very low. It does not matter whether the supply is AC or DC; a lamp would have the same brilliance at 230 V (AC) as at 230 V (DC).
As a rule of thumb for fixed-value resistances, a 10% drop in voltage results in a 19% drop in power.
What motor can only operate on alternative current?
The name of the motor that can only operate on alternative current is called the AC motor. The AC motor consists of 2 basic parts with a rotor that is attached to the output shaft.
A TPN MCCB is a three phase neutral molded case circuit breaker. This type of circuit breaker is commonly used in low voltage power distribution systems.
Commutator
What is the high leg in a three phase 480 panel?
there isnt a high leg in a three phase 480v panel only on 240v panels
What are the measurements done by digital multimeter?
Digital multimeters are quite clever things. They can measure multiple values. The most common measurements are:
Voltage - measured in volts (v)
Current - measured in amperes (A)
Resistance - measured in ohms (omega greek symbol) Sorry, I don't know how to type it.
What is magnetic line voltage motor starter?
A motor starter is a contactor (heavy duty relay) which acts as a remote-controlled on/off switch between the supply and the motor. Its operating coil is energised through an auxiliary stop/start circuit. It also incorporates overload function which will automatically disconnect the motor in the event of a sustained overload current.
What is does EED electrical processor stand for and where is this located?
in fuel injector system what is EED? where is it located?
