Download Capacitor as power factor improvement it`s

Capacitor as power factor improvement
it’s installation and location
Anubhav Ranjan Tiwari
M.Tech Scholar
Lovely Professional University
Punjab
[email protected]
1.
Abstract
In this paper we are using a capacitor for
improvement of power factor and it’s installation and
location is presented. Improving the power factor
means reducing the angle of lag between supply
voltage and supply current. Capacitors installed near
the loads in a plant are the most economical and
efficient way of supplying these kilovars. Capacitors
can be Install between the contactor and the overload
relay, the upstream circuit breaker and the contactor
and also Install at the main distribution bus.
2.
Aditya Gaddam
M.Tech Scholar
Lovely Professional University
Punjab
[email protected]
capacity, improve voltage and reduced value of your
power losses.
3. How capacitor works
Induction moters, moters transformers and there are
so many electrical loads which require magnetizing
current (kvar) as well as actual power (kw). So for
obtaining the apparent power from the right angle
triangle kva2 = kw2+kvar2. For reducing the value of
kva which is required for the any load. It is important
to shorten the line that shows the kvar. This is
precisely what capacitor do
.
Introduction
The measure of electrical efficiency is known as
Power Factor. The motors and other inductive
equipment in a plant needs two types of electric
power. One type is working power, determined by
the kilowatt (kW). Secondly, inductive equipment
needs magnetizing power to produce the flux
necessary for the operation of inductive devices. The
unit which we are using for the measurement of
magnetizing or reactive power is the kilovar (kVAR).
The working power (kW) and reactive power
(kVAR) combindly make up apparent power which is
measured in kilovolt tamperes (kVA). Most of the
AC power systems require both kW (kilowatts) and
kVAR (kilovars). Capacitors are installed near the
loads in a plant are the most economical and efficient
way of supplying these kilovars. Low voltage
capacitors are basically a high reliability
maintenance-free device. On the spot delivery of
magnetizing current provided by capacitors means
that kilovars do not have to be sent all the way from
the utility generator to you. This relieves both you
and your utility of the cost of carrying this extra
kilovar load. The utility charges you for this reactive
power in the form of a direct, or indirect power factor
penalty charge. In this way, you'll get system
By supplying kvar at the load, the capacitor relieve
the burden of carrying extra kvar. This makes the
transmission/distribution system more efficient. And
reducing cost for the utility and their consumers.
Selection of kvar for three phase moter To select the required amount of kvar required to
correct the power factor we should have three
informations:
 Kw
 Existing power factor in percent.

Desired power factor in percent.
5.
4.
Installation recommendation
Option - A
 Install directly at the single speed induction
motor terminals (on the secondary of the
overload relay).
Advantages l Can be switched on or off with the motors,
eliminating the need for separate switching
devices or overcurrent protection. Also, only
energized
 when the motor is running. Since kVAR is
located where it is required, line losses and
voltage drops are minimized; while system
capacity is maximized.
Disadvantages Installation costs are higher when a large
number of individual motors need
correction.
 l Overload relay settings must be changed to
account for lower motor current draw.
OPTION B –
 Install between the contactor and the
overload relay.
With this option the overload relay can be set for
nameplate full load current of motor. Otherwise the
same as Option A.
OPTION C
 Install between the upstream circuit breaker
and the contactor.
Advantages Larger, more cost effective capacitor banks
can be installed as they supply kVAR to
several motors. This is recommended for
jogging motors, multispeed motors and
reversing applications.
DISADVANTAGES:

Since capacitors are not switched with the
motors, overcorrection can occur if all
motors are not running.*
 Since reactive current must be carried a
greater distance, there are higher line losses
and larger voltage drops.
OPTION D - Install at the main distribution bus.
ADVANTAGES:

Lower installation cost, since you install
fewer banks in large kVAR blocks.
DISADVANTAGES:
 Overcorrection can occur under lightly
loaded conditions.
 A separate disconnect switch and
overcurrent protection is required.
Power Factor Correction Capacitors on
Reduced Voltage Motors and Multi-Speed
Motors
The following shows capacitor connections for
typical starting circuits for reduced value of voltage
and multi-speed motors. Variations in these circuits
do exist. It is important that your circuit exactly
matches the circuit shown here before applying
capacitors. Failure to do so may result in damage to
the motor. The main contacts.
shown in the diagrams below as M1, M2, M3,
reference the contacts that must be closed to start or
run the motor. Capacitors should be connected on the
motor side of the main contacts.
h = calculated system harmonic
kVAsc = short circuit power of the system
kVAR = rating of the capacitor
Harmonic values of 5, 7, 11, and 1 3 should be
avoided as they correspond to the characteristic
harmonics of non-linear loads. The harmonic value of
3 should also be avoided as it coincides with
harmonics produced during transformer energization
and/or operation of the transformer above rated
voltage.
7.
Conclusion
in this paper we are using capacitor for power factor
improvement by means of capacitor we are
improving the power factor and it’s installation and
location of the capacitor bank in the system is also
presented.
8.
6.
Consider harmonics when applying
capacitor
System harmonics is to be considered when we are
applying power factor correction capacitors.
Although capacitors do not generate harmonics,
under following conditions they can amplify existing
harmonics. Harmonics are generated when non-linear
loads are applied to power systems. These non-linear
loads include adjustable speed drives, programmable
controllers, induction furnaces, computers, and
uninterruptible power supplies. Capacitors can be
used successfully with nonlinear loads when
harmonic resonant conditions are avoided. To
minimize the occurrence of harmonic resonance, the
resonant harmonic of the system including the
capacitor should be estimated. The resonant
frequency can be calculated by:
where
References
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