roopesh
{ City } london
< Country > united kingdom
* Profession * sr.design engineer
User No # 21475
Total Answers Posted # 50
Total Answers Posted for My Questions # 105
Total Views for My Questions # 272577
Users Marked my Answers as Correct # 1497
Users Marked my Answers as Wrong # 456
Why we should use delta connection in primary and star
connection in an distribution transformer, which converts
400v a.c. voltage to 33kv.
Answer
availability of neutral point makes useful for earth fault
relay operation.
Delta connection having requirement of 3 conductors and
itself is long distance, with less current and higher
voltage. So economical way is delta at high voltage side
and star at low/ or consumer end.
| Is This Answer Correct ? | 55 Yes | 12 No |
Question { 14888 }
what is the effect when the shunt field winding is opened
in dc shunt motor (i) at the time of starting ? (ii) in
running condition ?
Answer
since the winding not energized, there will not be magnetic
field and at the same time armature being energized. so the
effect is ,a low resistance path being energized, so there
are chances of armature winding damage.
During running condition:
As soon as the field winding got de-energizes, the magnetic
field becomes close to zero(practically there will be some
residual magnetism), and speed of the motor will be much
higher and ultimately, the rotor will will be
damaged(mechanical parts).
| Is This Answer Correct ? | 16 Yes | 6 No |
A 100 MVA transformer may be cooled with?
Answer
best method for cooling such transformer is nitrogen
cooling or hygrogen cooling.
But this method is too costlier and having best overall
efficiency.
| Is This Answer Correct ? | 8 Yes | 1 No |
From, which load current range ( upper - lower limit
current)can Air circuit breaker used for in electrical
circuit.
Answer
with some safety margin and some future capacity also to be
considered.
| Is This Answer Correct ? | 1 Yes | 1 No |
Question { 8727 }
How to calculat size of copper & aluminium ?
Answer
following facts to be considered:
1.Maximum load current.
2.under ground or overhead laying
3.max. temperature withstanding capability of cable insulation.
4.max. voltage stress withstanding capability of cable
insulation.
5. distance of load from the power supply
6. AC/DC supply and frequency .
| Is This Answer Correct ? | 10 Yes | 0 No |
What will happen if 230V DC motor connected to 230V AC
Supply?
Answer
with AC supply:
1.Rotor speed will be less than the rated speed.
2. Rotor produced less torque and max. will be very less.
3.Core and copper loss will be more.
4.high sparking at brush, there by reduced life.
5.Motor gets heated up easily.
| Is This Answer Correct ? | 156 Yes | 13 No |
Why dc Supply used in Control circuit.
Answer
system, and there are many areas, where the system is to be
monitored even if there is no power supply at all.(eg: in
sub stations. during lightning stroke its very necessary
that, the system to be isolated.)
In this case, DC is the only choice that, we can provide
with battery supply. So most critical control systems
designs with DC only( pref. 24 to 48 volts DC)
| Is This Answer Correct ? | 21 Yes | 6 No |
what are the affects of loose connection in electrical
circuit.
Answer
1. Spark b/w cable and equipment.
2. Damage of cable lugs.
3. Heating of any insulation nearby.
4. can ignite any inflamable material near by
5. voltage reduction b/w the terminals etc.
| Is This Answer Correct ? | 79 Yes | 6 No |
Question { 11538 }
what happens to the speed of a DC series motor when series
field winding is removed?
Answer
as the excitation deceases. But if we remove the excitation,
the motor speed will tend to increase, because of the
residual magnetism, and the rotor winding will burns off,
because of short circuit.
| Is This Answer Correct ? | 4 Yes | 4 No |
Input power is 380 - 450 V but with 45 - 55 Hz frequency -
desired output is 415 V and 50hz with 1% variation
permissible. CVT / Servo dont stabilize the Frequency -
what is best solution??
Answer
such frequency variable supplies.
| Is This Answer Correct ? | 7 Yes | 0 No |
1> what r different types of fault in cables? How will u
locate and test these faults?
2> why earth wire is provided on top throughout the
transmission line. why not only on towers? How much area it
can protect?
3> what r different types of transmission losses? How power
loss can be minimized?
4> what is the % of power loss on transmission lines?
Answer
leakage faults and insulation breakdown.. Due to these,
some part of the cable( specifically, underground) get
heated up and burst.
Locating such faults, some wheastons bridge system can be
used.
2. the earth wire above the conductor can protect the live
conductor from lightning surges.up to 30 deg.down max it
can protect from horizontal level. In distribution system
normaly does not require bcz the height of such post may be
as small as 11 mtr, but that of 33kv or 220kv may be as
high as 28 or 35 mtr.
3.transmission losses are copper heat loss and corona loss
and insulation loss.( refr Power system by UPPAL)
4.6-12%
| Is This Answer Correct ? | 19 Yes | 2 No |
Question { Alkem Labs, 19616 }
What is the diffrence between four strock and two strock ic
engine
Answer
rotation but 4 strokes are not.
| Is This Answer Correct ? | 14 Yes | 8 No |
What is the use of conservater, bucchos relay, breather in
a transformer?
Answer
the circuit will be tripped off as soon as the coil attains
a pre determined temp.
Conservator is to store additional cooling oil, and same
oil can be make use later also.
Breather is to absorbe moisture contents from air which
sucks in while the oil get expanded.
| Is This Answer Correct ? | 90 Yes | 22 No |
