Question { L&T, 7594 }

why is used for starters for staring motors?

Answer

to provide OVER LOAD RELEASE COIL(Relay) to save the moto winding from more current than rated.

Question { Bhel, 7354 }

Why we use startor to the motor?

Answer

for smooth control and provide trip system....

Question { Bescom, 8190 }

in three phase 11kv transformer (11kv/433v)
input( R,Y,B) output (X,Y,Z,N) the connection as follows
1 phase R -open
2phase y connected to both R and y of input]
3phase B- B
what is the output voltage X to N ,Y to N , Z to N

Answer

phase voltage ie. voltage b/w x-n. y-n and z-n is 250 volt each but line voltage b/w x to y = 0 volt y to z= 433 volt and z to x = 433 volt

Question { Cura HealthCare, 4704 }

If we tell 60 sq.mm. 3-1/2 core cable,then what does it mean
?
1) Each core section in the whole cable is of 60 sq. mm.
2) The whole cable is of 60 sq. mm. which is sub-divided
into 3-1/2 core.

Answer

There no such size(60sqmm)of cable available. Yes 70sqmm size cable. Size means cross-section area(pi D sq /4) of individual core of a cable. Three and half means, same size of three cable (RYB) aod nutral core is approximately half size of other.

Question { 3820 }

why dc series motor high speed motor

Answer

Flux produced in field of DC series motor is less and armature current is slightd reduced at starting time because very low value of resistance is used in dc series stator and by study these relation and effects, we sure that there is no back emf produced in dc series motor that is why ....

Question { 6328 }

What should be the BDV value of a new transformer oil

Answer

For 11kv suppy it is 40kv/2mm at normal temprature is ok. As per my experience it is reach upto 125kv/2mm at 40°c after filtration but we keep it 60kv/2mm NB-Below 24kv/2mm is rejected oil.

Question { Sabic, 6672 }

what is the formula to get the 3 phase motor winding resistance? for example, i have 460v and 3A ? what would be the per phase winding resistance? thank you..

Answer

it is about 6 ohm.

Question { 6276 }

how much the voltage & resistance should be ,between earth
& neutral points.?& why?

Answer

the resistance b/w earth and neutral 1.8 kohm is accepted and in 3phase supply voltage b/w earth and neutral 3v to 20v is accepted.

Question { 9075 }

Which one hurts more AC or DC Current ?

Answer

the same rating of AC & DC Voltage the man get more voltage in ac which is more than RMS value but injude more in DC supply.

Question { 14709 }

A 60w bulb & a room heater are connected in series.if 60 w
bulb is replaced by 100w then what will be the effect on
heater out & why?

Answer

by replacing 100w bulb the total resistance is decreased then the current flow the circvit will increase
therefore the heater giue more heat.

Question { 1883 }

we know the value of the power factor is 0.8, we know the
power factor is not depends upon the load ,then why we cant
design the power factor in transformer ?

Answer

power factor I.e the value of cosine angle between voltage and current .it is 0,6(or less) to 0.9(max 0.99) but it is not fix as 0.8 that is why transformer is rated.

Question { 2751 }

choose the non-switch device
(A) transformer
(B) diode
(C) transistor
(D) IC

Answer

transformer

Question { 6971 }

If 12 men and 16 boys can do a piece of work in 5 days and,13 men and 24 boys can do it in 4 days, how long will 7 men and 10 boys take to do it,

Answer

according to questions 12men =16boys # 5 ......eq(1) and 13men + 16boys # 4days .........eq(2) from equation 1 we get60men + 80boys # 1 days......eq(3) and from equation 2 we get 52men + 96 boys # 1day......eq(4) from equation 3 & 4 we can calculate that when 8 men reduced there is extra 16 boys required to finish the same job in same time, therefore efficiency of 1 man + 2 boys. putting this efficiency in equation 3 we get 60 men + 40 men (=80boys) # 1 day or 100men # 1day or 1man can do work 1/100 parts of job per day. and 1 boy can do work 1/200 parts 0f job per day. therefore 7men+10boys can do work 7/100+10/200=24/200 parts of job per day and to finish they need 200/24 days that is 8.3 days

Question { WNS, 13333 }

3 small cubes have the sides 3cm, 4cm, 5cm respectively. These are melted to form a large cube. Find the ratio of total surface area of the smaller cubes to that of the larger cube.

Answer

3:4:5:6

Question { WNS, 13333 }

3 small cubes have the sides 3cm, 4cm, 5cm respectively. These are melted to form a large cube. Find the ratio of total surface area of the smaller cubes to that of the larger cube.

Answer

Volume of new cube (3*3*3+4*4*4+5*5*5)=216 cubic cm
Side of new cube cube root of 216= 6cm
Therefore total surface of new cube 6*6*6=36 sq cm