Question { Bhel, 14761 }

what is ups?how its works?and what is there in static
switch how it works?

Answer

Working Principle of UPS:-
UPS is for the purpose to give un-
interruptible power
supply. This stores the energy in the form of DC by the
controlled rectifier (AC - DC converter) and discharge the
energy in the form of controlled AC by inverter (DC - AC
converter) so as to provide continuous power supply. Here
the back up is derived based on the requirement.

types:
1. Online Double convertion UPS (Normal High capacity UPS)
2. Online Delta convertion UPS (New technology offline
using buck boost Transformers)
3. Offline UPS (economical UPS medium capacity UPS 3 -
30KVA also available in higher capacity)
4. Line Interactive UPS (lower capacity UPS 300VA - max5KVA
output will be Squasi Sinewave).

UPS are used in home, medical, IT and industrial where the
critical load is used.


Static Transfer Switches :-

Static transfer switches in single
phase and 3 phase outputs suitable for use with two
synchronised or non synchronised input power sources, the
transfer switch provides a single output to the critical
load. This series of static transfer switches can operate
with the default source selected as A or B to feed the
critical load, on failure of the selected source the load
will be transferred in synchronism to the alternative
source. Sizes are available from 10kW to 1000kW with three
switching elements as standard for the three phase system,
a manual wrap around bypass switch is also provided. A
power flow status mimic and alarm indicating mimic with
separate digital or analogue metering is fitted as a
standard feature.

Question { L&T, 11894 }

What is Skin effect of the cable?

Answer

The skin effect is the tendency of an alternating electric
current (AC) to distribute itself within a conductor so
that the current density near the surface of the conductor
is greater than that at its core. That is, the electric
current tends to flow at the "skin" of the conductor. The
skin effect causes the effective resistance of the
conductor to increase with the frequency of the current.
Skin effect is due to eddy currents set up by the AC
current.

Question { GMR, 7314 }

What is hysteresis losses?

Answer

Hysteresis loss is a heat loss caused by the magnetic
properties of the armature. When an armature core is in a
magnetic field, the magnetic particles of the core tend to
line up with the magnetic field. When the armature core is
rotating, its magnetic field keeps changing direction. The
continuous movement of the magnetic particles, as they try
to align themselves with the magnetic field, produces
molecular friction. This, in turn, produces heat. This heat
is transmitted to the armature windings. The heat causes
armature resistances to increase.

For More Details Visit
http://www.tpub.com/content/doe/h1011v2/css/h1011v2_89.htm

Question { 6905 }

How much pole motor can be desion for 415 volt ,50 hz.Power
supply. in pratical condition .

Prakash veer singh

Answer

Normaly its 4 Pole.

Question { 5504 }

How can you test the vector group of power transformers?

Answer

A Vector group is the International Electrotechnical
Commission (IEC) method of categorizing the primary and
secondary winding configurations of three-phase
transformers. Within a polyphase system power transformer
it indicates the windings configurations and the difference
in phase angle between them.[1]

The phase windings of a polyphase transformer can be
connected together internally in different configurations,
depending on what characteristics are needed from the
transformer. For example, in a three-phase power system, it
may be necessary to connect a three-wire system to a four-
wire system, or vice versa. Because of this, transformers
are manufactured with a variety of winding configurations
to meet these requirements.

For More Information Log On to:-

http://en.wikipedia.org/wiki/Vector_group

Question { 5176 }

hi friends iam collecting details about motor,generator &
transformer so send some web links to about motor,generator
& transformer ,please help me .i need your help.thank u

Answer

For Motors:-
http://www.pacontrol.com/download/Tutorial-
Motor-Basics-Lecture.pdf

For Transformers:-

http://www.federalpacific.com/university/transbasics/transba
sics.html

For Generators:-
http://www.federalpacific.com/university/transbasics/transba
sics.html

Question { 6514 }

Can someone tell me how to calculate the size of a power
cable? What are the factors involved in cable sizing?

Answer

Cable size is dependent upon the load(s) you wish to supply
power too. You have to know the maximum current you can be
expected to carry on a particular circuit BEFORE choosing a
cable.

Once you know the load, you need to choose a cable size
rated to carry at least that much current, preferably more
as a safety factor.

So if you are planning on running several electrical
devices with a combined current of 20 amps, you need a
cable sized to carry at least 20 amps, and slightly more.

To calculate the size of a power cable,pls refer the
following table LINK:-

http://www.electrician2.com/calculators/wireocpd_ver_1.html

Question { 5452 }

Could anyone clarify my wondering.
What is the difference between knee point voltage and
saturation voltage of the CT.
Is their any formula to calculate these values?

Answer

The knee point
is a ten percent ratio error between the
primary input current and the corresponding secondary
output current.

The saturation point involves determining the secondary
voltage necessary to drive the measured current through the
impedance of the secondary circuit.

For More Details,Pls visit
http://www.control.com/thread/1026243854

Question { KPTCL, 16140 }

what will hapen if secodery circuit is open of current
transformer

Answer

The CT Will Burn....

Why does opening a CT's secondary cause dangerously high
secondary voltage?
With the flow of both primary and secondary currents the
transformer's exciting current is very low. The secondary
current mmf serves to keep the magnetizing flux in check!
If the secondary now opens the primary current mmf produces
an exciting current 'orders of magnitude' greater than
normal. And, the resultant large increase in flux density
produces an extremely high voltage in the secondary.

Regards,
Thowsif.

Question { 3573 }

define reluctance motor & its operation ?whether its
operating single phase or three phase ?

Answer

A reluctance motor is a type of synchronous electric motor
which induces non-permanent magnetic poles on the
ferromagnetic rotor. Torque is generated through the
phenomenon of magnetic reluctance.

For More Details,Visit the following link:-

http://en.wikipedia.org/wiki/Reluctance_motor

Question { 5123 }

dear friends plz send link about reluctance & universal
motor .thank u

Answer

Hi Ramaya,
Whats ur Qualification??

Question { 5123 }

dear friends plz send link about reluctance & universal
motor .thank u

Answer

I'm also BE,Which Colg..

Question { 3604 }

what will hapen if secodery circuit is open of current
transformer
WHy neutral to ground trips when neutral touches the ground

Answer

The CT Will Burn....

Why does opening a CT's secondary cause dangerously high
secondary voltage?
With the flow of both primary and secondary currents the
transformer's exciting current is very low. The secondary
current mmf serves to keep the magnetizing flux in check!
If the secondary now opens the primary current mmf produces
an exciting current 'orders of magnitude' greater than
normal. And, the resultant large increase in flux density
produces an extremely high voltage in the secondary.

Regards,
Thowsif.

Question { 3994 }

pls send link about servo motor

Answer

Hi Ramaya,I'm frm B'lore,

I dng BEE in Evng. BMS Colg.

wt abt u??

What ever u need,send me those detials,so I can fwrd u d
realted links.

Question { 6397 }

what is appearent power?

Answer

Apparent power is the combined power value that is obtained
by allowing for the different values of current and
voltage. Essentially, the measure of apparent power is
achieved by multiplying the applied voltage to the current
generated. Most electrical systems operate by the use of
apparent power.

There are a few basic understandings about the nature of
apparent power that help to define the nature of the power.
Components of both reactive and real power must be present
in order for apparent power to exist. That is, the load
must be both reactive and resistant in order for the flow
of apparent power to take place, and thus create a means
for measuring the nature of the generated power. In
addition to the presence of resistant and reactive loads,
it is also important to determine the watts involved in the
current as well. Just as in determining the rate of any
complex power, knowing the watt value is key to
understanding the nature of apparent power.

In the actual calculation of apparent power, the number of
volts is multiplied by the number of amps. Results of the
calculation are presented in terms of volt-amperes reactive
and real power. This simple multiplication of voltage and
current makes it possible to ensure that the flow of
apparent power is sufficient to operate devices designed
for a given level of power, as well as ensure the flow of
apparent power can be handled by the components within the
device. Within this context, the measure of apparent power
is very important to manufacturers, as it allows them to
ensure that all products are within the standards
applicable within the jurisdiction.

Measuring the flow of apparent power is also critical in
the tasks of wiring public buildings and residences
properly. Plants must ensure that all electrical wiring and
additional components will adequately support the power
supply needed to drive large machinery without overloading
the circuits or wiring systems. Power suppliers themselves
will measure apparent power to make sure that the flow of
harnessed energy into homes and other buildings is
maintained within the safety standards that apply to the
area and type of structure.