Capacitor
Capacitor: capacitor is a device which stores energy in it in the form of electrostatic.
*It stores AC and passes DC.
*It is independent of current
*It is denoted by C
C = Q/V
Where Q = charge in columb
V = potential difference between the plates
C = capacitance
We know, I = charge/time = Q/t
Hence Q = i*t
Therefore C = Q/V = (i*t)/V
Hence V = Q/C = (i*t)/C
* capacitor is also named as condenser.
The factors on which capacitor depends:
1.The plate area of condenser
2.The distance between the plates
3.The nature of dielectric.
We have another formula to calculate the capacitor value
C = (£*A)/d
Where C = capacitance value
£ = permeability of the dielectric material
A = cross-sectional area of the capacitor
d = distance between two plates
Capacitor inner view
Capacitor inner view
For a capacitor the current through it, is proportional to the rate of change of voltage across it.
I(t) α dv(t)/dt
I(t) = C* dv(t)/dt
C=capacitance &proportionality constant
Voltage across capacitor is given by
V(t) = 1/C ∫ i(t) dt volts
Power across the capacitor is given by P = V(t)*i(t) watts
Energy storage capacity of the capacitor is W = ½ CV^2(t) joule
Series & parallel connections :
Capacitors are connected in series
1/Ceq = 1/C 1 + 1/C 2
Capacitors are connected in parallel
Ceq = C 1+C 2
The below video shows the working of capacitor
The below video shows the working of capacitor
Colour codings for the capacitor
colour
|
First
figure
|
Second
figure
|
multiplier
|
Tolerance
|
Black
|
0
|
0
|
1
|
C < 10 PF
|
Brown
|
1
|
1
|
10
|
C + 1 PF ,
C – 1 PF
|
Red
|
2
|
2
|
100
|
C > 10 PF
|
Orange
|
3
|
3
|
1000
|
C + 20% ,
C – 20%
|
Yellow
|
4
|
4
|
10000
| |
Green
|
5
|
5
|
_
| |
Blue
|
6
|
6
|
_
| |
Violet
|
7
|
7
|
_
| |
Grey
|
8
|
8
|
0.01
| |
White
|
9
|
9
|
0.1
|
Types of condenser:
1.Mica condenser
2.Variable air condenser
3.Electrolytic condenser
Mica condenser:
*The mica condensers are consisting of metal foil sheets forming the coating and separated by a mica sheet or paraffin paper as dielectric.
*These are used in the circuit where fixed values of condensers required.
Variable air condenser:
*These condensers consist of number of semi circular plate of sheet aluminium mounted together by a metal rod &capable of moving in between a number of fixed aluminium semi circular sheets.
*The capacity increases when the rotating sheets are moving into the fixed sheets.
*these are used in radio receives for turming the receiver to a particular transmitting station.
Electrolytic condenser:
*These are having a very large capacity of 10 to 100HF.
*These are used in radio circuit &electric circuit.
paper dielectric capacitor:
*These capacitor consists of high potential difference without breaking down.
*Dry paper is a good insulator and have high dielectric strength.
*It consists of two rolls of aluminium foils or tin foils sandwiching a tissue paper rolled by a machine so that the final shape is small cylinder tube.
*These capacitors are available from 0.01F to 1.0F.
Rolled plastic (or)polyster type:
*polyster is a thermo plastic material
*At high frequencies it achieve better performance
*The manufacture process is same as paper capacitor
silver mica capacitors:
*It consists of mica plate with silver coating on both sides
*Silver is deposited by means on mica sheets
*By connecting in parallel the required capacitance is obtained
*The capacitor value ranges from 100PF to 200PF
Ceramic capacitors:
*These capacitors having high dielectric constant so, large capacitors obtained in small space.
*The ceramic capacitors are available in following forms
a.Disc ceramics b.Tubular ceramics
c.Moulded ceramics d.Button ceramics
*The disc type ceramic capacitor value ranges between 0.002μF to 0.1μF
*The tabular type ranges from 0.5PF to 1000PF.
The below figure shows the types of capacitors
The types of capacitors and their applications
Capacitor required in different circuits in a radio receievers
The types of capacitors and their applications
Type
|
Range
|
Application
|
Paper capacitors
|
1.5 to 2.5 M.F.D
350/400 v AC
|
For ceiling fans & Desert coolers
|
3.5 to 20 M.F.D
250/380/400 v AC
|
For fluorescent lamps
| |
3 to 36 M.F.D
400/400 v AC
|
For motors in Air conditioners, washing machines, water coolers
| |
Medium voltage
power capacitors
|
Basic unit output
1 to 30KVAR
Voltage 400 to 650v AC
|
For improvement of power factor in induction motors.
|
High voltage
Power capacitors
|
Basic unit output
Upto 200 KVAR
Voltage 3.3/6.35/9 KV
|
Used in factories, for improving the power factor of large induction motors, Transformers, Welding equipment, Transmission system.
|
Medium and high frequency
Power capacitor
|
10,000 HZ frequency
|
For induction furnances.
|
s.no
|
Type of circuit
|
value
|
Types of capacitors
|
1
|
Tunning circuit
|
500 PF
|
Variable capacitor
|
2
|
Oscillator circuit
|
500 PF
|
Variable capacitor
|
3
|
Rectifier filter circuit
|
8 PF to 100 PF
|
Electrolytic capacitor
|
4
|
Audio frequency stages
|
0.005μ F to 0.5 μF
|
Paper capacitor
|
5
|
Trimmes
|
70 PF
|
Variable capacitor
|
6
|
Padders
|
600 PF
|
Variable capacitor
|
7
|
R.F stages
|
50 PF to 100 PF
|
Mica capacitor
|
USES OF CAPACITOR
Capacitors in fluorescent tube :
1. The power factor improves, when connected in parallel.
2. The strobodcobic effect is minimized, when connected in series.
3. The sparklings are eliminated which occurs at the time of openings two contacts.
In motors :
1. The power factor improves, when connected in parallel.
2. When it is connected in series with the starting winding of single phase motors it splits one phase into two phases and gives starting torque to the motor.
thank you for information...
ReplyDeletethank you for information...
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