WHAT IS INVERTER: - - Webs

restmushroomsElectronics - Devices

Oct 7, 2013 (4 years and 1 month ago)

80 views


1

NTRODUCTION


Our project is based on pulse width technology. As the inverter is usually a device which
convert A.C power into DC power and vica versa.

In ordinary inverter circuits there is just conversion of AC to DC by using usual

Diode rectifier and t
ransistor for inverter purpose which are not reliable and protection of

Battery as well as circuit itself is very less

In our circuit of about inverter we are using PULSE WIDTH MODULATION
TECHNOLOGY and MOSFET for inverter purpose. The circuits have compl
ete
protection about the circuit itself as well as the battery. i.e. we can charge the battery
accordingly to our setting of charging current.

Also by using PULSE WITH MODULATION TECHNOLOGY our circuit is give the
completely stabilize voltage at the output

from (0
-
270) Volts as per the setting


VARIOUS PROTECTION AND STAGES OF INVERTER:
-





OCILLATOR CICUIT TO MAKE 50hz PULSES TO TRIGGER THE MOSFET
TO Get 50hz 230 V a c OUPUT.



CONVERSION OF AC TO DC AND VICA VERSA BY USING MOSFET.



OVER LOAD SENSING CICUIT



CHANGE OVER WORKING CIRCUIT



LOW BATTERY CUT CIRCUIT



CHARGING SENSING CIRCUIT



CARGING CONTROL CIRCUIT



AC MAIN SENSING CIRCUIT






















2





WHAT IS INVERTER:
-


A device that converts dc power into ac power at desired voltage and frequency is called
inverter. DC power input to the inverter is obtained from an existing power supply
network or from a battery. The configuration of ac to dc and dc to ac inverter is
called a
dc
-
linked converter.

This conversion can be achieved ether by transistors or by SCRs
or MOSFET. For low & medium power outputs, transistorized inverter are suitable
but for high power outputs SCR should be used . For low power s
elf oscillating
transistorized inverters are suitable, but for high power outputs MOSFET driven
invertors are more common than self


oscillating ones.



Inverter can be broadly classified into to types

1.

Voltage fed inverter

2.

current fed inverter

a voltage

fed inverter or voltage source inverter, is one whih the dc source has small or
negligible impedance. In other words, a voltage source inverter has stiff dc voltage source
at its input terminals.

A current
-

fed inverter or current source is fed with adjus
table current from a dc source of
high impedence from a stiff dc source. In this case output current waves are not affected
by load.



OCSCLLATOR CIRCUIT:
-


The oscillatory circuit is one of the important part of the inverter circuit. The main
requirement

the circuit i.e. to achieve the 50 Hz standard frequencies is achieved by this
circuit. For oscillatory circuit we use IC SG 3524 which also provide PWM technique for
the inverter operation.

The IC SG3524 is one of the important part in the whole circuit
. The internal working
and main description of IC SG 3524 is explained below.

IC SG3524 PIN DESCRIPTION:
-


Pin no 1:
-
> this pin is used as a feedback signal. This pin basically a input pin.

Pin no 2:
-
> this pin provides the response voltage regarding pin

16.

Pin no 3:
-
> this pin works as a output pin of oscillator circuit.

Pin no4 & 5:
-
> this pin is ground pin which attach the amplifier circuit.


3

Pin no 6:
-
> this pin used as a pre set pin.

Pin no 7:
-
> timing capacitor is attaching that pin to fix the oscil
lator.

Pin no 8:
-
> this pin is used for

ve supply purpose.

Pin no 9:
-
> this pin shows the function of PWM.

Pin no 10:
-
> this pin is a shut down input pin. It gives the 0.6v every time. If the pin give
more voltage than the inverter not works.

Pin no 11:
-
>

this pin give the mos drive voltage to oscillator circuit.

Pin n0 12 & 13:
-
> that pin used for getting the +ve supply.

Pin no 14:
-
> that pin give MOS drive voltage.

Pin no 15:
-
> this pin also used for +ve supply.

Pin no 16:
-
> this pin give 5v reference vo
ltage.

FIG :
-

INTERNAL VIEW OF IC SG 3524 :
-



4

WORKING OF OSCILLATOR CIRCUIT:
-

Firstly give the +ve supply from the +ve terminal of battery through pin no. 15 and give
the negative supply to the pin no. 8 of IC SG3524 Pin no. 12 & 13 i
s used for output pin
and pin 6no . 6&7 used for oscillator purpose. Timing capacitor is connected pin no. 7
and this pin is attached to the capacitor and it is grounded also. This pin basically creates
50hz frequency. Pin no. 6 is a timing resistance pin
with the help of that pin we can
change the resistance which stabelize the frequency.


With the help of variable resistance value we can attach the variable pin with the help of
variable p we can adjust the required fr. Demand oscillator signal going to IC
. In internal
structure of IC flip
-
flop are attached that show one time +ve signal & other time show

ve signal . The output is given through npn internal buses of ic . Emitter is attached ic pin
13& 14. That pin are also grounded pin as shown in fig.


Th
e collector of transistor is attached 12 & 13. From the help of pin 12 & 13.180 phase
50hz phase is obtained. With the help of pin 6& 7 we can oscillate the circuit. Pin no. 12
& 13 also called MOS drive voltage ckt the pulses of pin no . 13 is amplify t
hrough t11,
t13,t14. The voltage of pin no.12 is amplify through t12,t15,t16. Two channel are
working of MOS driver circuit . When we use two channel then please check frequency
of both the channels are same and voltages are also same. That voltage basical
ly lie 3 to
4v.we can see both channels show 50hz fr.

We got the signal going one after the other at both channels. The procedure of on
-
off of
both channels are very fast . In one second that on
-
off procedure is 50 turns. That
procedure is known as switc
hing procedure. We can generate the current at secondary of
transformer. 270v tapping is used with relay than give the output signal to output circuit.











5

WORKING OF OSCILLATOR:
-










6

PULSE WIDTH MODULATION TECHNOLOGY (PWM TE
CH.)


Voltage control in single phase system:
-
>


AC loads may requires constant voltages at their inputs terminals . when such loads are
fed by inverters, it is essential that outputs voltage of inverter is so controlled as to fulfill
by requirements of ac

loads .examples of such requirements are as under:
-
>


1>

An ac load may require a constant input voltage through at different levels. For
such a loads any variation in dc inputs voltages must be suitably compensated in
order to maintain a constant voltage at

the ac loads terminals at a desired levels.


2>

In case inverter supplies power to a magnetic circuit such as an induction motor,
the voltage to frequency ratio at inverter output terminals must be kept constant .



The various methods for the control of

output voltages of inverter are as under:
-
>


a>

External control of ac output voltage

b>

External control of dc input voltages

c>

Internal control of inverter


Internal control of inverter :
-
>


Output voltage from inverter can also be adjusted by exercising a cont
rol with in the
inverter itself .The most efficient method of doing this is by plus width modulation
control used with in an inverter.


Pulse width modulation control:
-
>


In this method a fixed dc input voltage is given to the inverter and a controlled ac
output
voltage is obtained by adjusting the on and off period of the inverter components.This is
the most popular method of controlling the output voltage .


Advantages :
-
>


The output voltage controlled with this method can be obtained without any additio
nal
components.


With this method lower order harmonic can be eliminated along with its output voltage
control . As higher order harmonic can be filtered easily the filtering requirements are
minimized.


The main disadvantages of this method is that the sc
rs are expensive as they must possess
low trun on and trun off time .



7

Constant frequency system:
-
>


The on time Ton is varied but chopping frequency f is kept constant. variation of Ton
means adjustment of pulse width as such this scheme is called pwm.

T
his scheme has also been referred to as time ratio control.



WORKING OF PWM CIRCUIT:
-

Stable pwm basically used to maintain the 220v output fr.if the feed back of ic is properly
Work than pwm work very accurately. If it is not feed back properly them out
put at the
Pin 12&13 show not accurate output.the duty cycle change many time and effect the
output Give the output270v at pin no1(cn
-
4).and through pin 1 can also given output
R36,d15,d16,d17&d18&bridge rectifire.that rectifier change the ac supply t
o dc.

The five Terminal of bridge rectifier is attatched ic 4n35 pin no 1&five terminal attatched
pin no 2 . The Internal structure show one led & photo transmission. Pin no i&2 are
connected lrd when The invertor joined dc mode than led show lighting. Th
e light fall
internal photo Transmission of IC than transistor show working. pin 5 is attached
transistor collector & Pin 4attatch photo transistor emitter.121v supply is given to pin5 .
This supply is given r45 Through ic pin 1.c has also operation simpli
fier that works as
error voltage amplifier.


That Amplifier attatched pin 1,2,9. Pin no1 inverting, pin no 2 non inverting supplies
given to pin no4 if the voltage level going increases & decreases then it effect the pin
no9 . But pwm maintain The output
. This is not matter duty cycle work up/down. If pwm
not work it effect the output. Pin no 9 attached to vr3 , with the help of vr3 we can
maintain the output voltage.



WORKING OF VARIOUS STAGES IN INVERTER:
-


As the inverter is used to convert ac to dc
and vica versa. For proper working of the
inverter circuit the protection operation is also main requirement other then the basic
operation of the circuit i.e. to convert into ac to dc and ac to dc.

The main stage of inverter circuit are:
-


1. OCSILLATOR

CIRCUIT:
-


Oscillator circuit is the main part of the circuit which provide the required trigger signal
to the power circuit of inverter to achieve the inverter operation with required output
frequency and output voltage

In our circuit the oscillator circ
uit is also provided with the pulse with modulation circuit
so that the inverter operation should be in constant voltage mode


8

The main component used in this circuit is IC SG3524, which is inbuilt with oscillator
circuit and PWM circuit


MOSFET CIRCUIT or

POWER CIRCUIT:
-


Mosfet circuit is the power circuit of our inverter circuit .

Its carries the load current as well as the battery charging current. The mosfet are worked
in enhancement mode for conversion of dc to ac. The operation of ac to dc also carri
ed
out by the mosfet circuit because the mosfet have a inbuilt diode that convert ac to dc

In out circuit we use three MOSFET in parallel to share the current as equally and for
proper operation according the rated load condition.


A FET is a device in
which the number of current carriers available in conducting region
is controlled by the application of an electric field on the surface of semiconductor or it is
a device which operates an the principles that the thickness and hence the resistance of a
co
nducting channel of semiconductor may be regulated by the magnitude of a potential
applied to its input terminal

A field effect transistor has a very high input resistance, less noise better thermal stability
then the bipolar transister.

The mosfet circuit

is shown in fig with its associate’s circuitry.


INVERTER POWER CIRCUIT
:
-





9




As the basis operation of the inverter circuit to convert ac to dc and ac to dc. The
complete operation of the inverter circuit required various sensing c
ircuit and the
protection circuit

As we mention earlier the various protection and sensing circuits that we are
Applying in our circuit i.e.




OVER LOAD SENSING CICUIT



CHANGE OVER WORKING CIRCUIT



LOW BATTERY CUT CIRCUIT



CHARGING SENSING CIRCUIT



CARGING CONT
ROL CIRCUIT



AC MAIN SENSING CIRCUIT


Now various protection and sensing circuits with their associate circuitry are
explained below.


OVERLOAD PROTECTION AND SENSING CICUIT:
-


The overload protection is essential for the proper operation of the inverter ci
rcuit.

If the overload protection is not provided in the circuit then overloading may causes
the temperature rise of the transformer as well as the MOSFET of the power circuit of
the inverter.

This protection is provide in the circuit in such a way that fi
rst we sense the current at
Mosfet drain and source terminal continuously, and we can set the sensing current
with some reference value to achieve the desired load current operation of the circuit.

The overload sensing circuit with its explanation is as be
low.



Working of overload section:
-
>

When the load is more its rated value then there is a risk to the mosfet circuit.
Therefore in The inverter circuit, we have provide the prevision for shutdown the
inverter during Overload . For overload protection

we are using IC7(lm339) pin no.
1,6,7,10,11 and 13 when the Inverter is overloaded we got overload indication from
0.1 ohm resistance in the Mosfet Source circuit . This signal sent to pin no .6 and 7.
Pin no. 7 is inverting pin Vr5 is used to set the ove
rload voltage. By resetting the vr5,
we can change the voltage of pin no. 7. The pin No 1 is the output pin & pin no .6 and
7 are the input pin. During the normal load pin no 6 & 7
having equal voltage and pin
no 1 have more voltage than 7.7v. Which give t
he base of T17 And activate the
transistor and give 5 volt. Approximately. Further this voltage give to the Pin no. 7 of
IC 555 through d33 and r83 . An IC 555 work as multivibrator & give overload signal
to led . When there is no overload IC7 voltage is
more the pin no 6. Therefore pin no
1 Give high output and pnp t17 have more voltage at the base then emitter, there is no

10

current Source and there is
zero voltage at the collector. In the collector side of T17
the pin no. 7 Of ic 555 is connected and its
output at the pin no 3 go to the base of t18
. And the output of T18 becomes high. Which is used in the following section of
inverter circuit.



To shut down pin ic6.



To led through r112.



To buzzer through r63.


MAIN SUPPLY SENSING
CIRCUIT:
-


The inverter a
nd converter operation never run simultaneously. When there is inverter
operation then there is no any charging operation. Because we are using Mosfets in
the circuit that are used both for inverter as well as rectifier due to inbuilt diode in the
Mosfet

T
herefore the circuit should have a provision that when there is inverter operation
then the charging operation should be cut out.

Therefore the circuit should have a sensor the check that the main supply from the
distributor is coming or not, which is achi
eved by a circuit which get the main supply
which is compare with the reference battery supply.

The main supply sensing circuit and its associate’s circuitry is shown in fig below.



Working of ac main sensing circuit:
-
>

To find out the ac main i.e for ac

sensing 0
-
18v / 1 amp transformer, t5 (lm 7812) and
Operational amplifier ic2 are used pin no 8,9,10 of ic2 (lm324) are used for ac main
sensing. Pin No 9 is ground pin. When we switched on ac main, +12 v supply is given to
pin no 10. Through r22, which i
s made from 0
-
18v
-
trigger transformer & regulator, lm
(7812) unregulating supply is given through pin no 9, through +ve terminal of rectifier &
r38. On pin no 10&9 approximately 0.5
-
3.5v are obtained. The o/p on pin no 8 is only 1v
including ac sensing plu
ses. These pluses are given to t1 base through r11. When pulse is
given to transistor it starts working on Collector ac main sensing pulse is obtained.







11


BATTERY LOW CHARGING

INDICATOR
:
-



In our circuit of inverter there is provision that the Batter
y not deep discharge in any
condition. If the battery is discharger below certain level then the its automatically cut
from the inverter operation, otherwise the deep discharging of battery occur and the
battery plates causes sulphation at its surface and
the life of battery is reduced

The circuit arrangement and its working is explained in circuit below.

In our circuit of inverter there is a provision of Low battery out that is when the voltage
of battery Come down below some specified value the inverter

circuit is shut down. for
this protection We use pin no 4,5
-
2 of IC3 which is operational amplifier. Internally
build in the ict. pin no 4 is Inverting pin and pin no 5 is non
-
inverting pin. Pin no 5 got a
battery supply through vrt and Rtt.when the volt
age of the battery is more than 10v than
output of pin no 4,5 at pin no2 is about 7v. Which is given to the base of t19, and the
transistor will not work due to high base Voltage that is zero volt at the collector of
transistor. and the emitter of transist
or got 8v.when the voltage of battery about 10v and
opp. pin no2 have got low voltage & also the Base of t19 got less voltage. And we got the
signal at the collector of t19 this collector Signal g given to the buzzer through d29. Also
this signal is given
through r62. Also this Signal is given to the pin no 10 that is shut
down pin of sg3524.therefore inverter is shut down by getting how voltage indication













12


BATTERY SIGNAL PROCESSOR CIRCUIT:
-













13



CHANGE OVER SENSING CI
RCUIT:
-


Usually in the inverter circuit the changer over from charging operation to inverter or
discharging operation is made by using supply from the main i.e. the relay is on when the
supply is coming and the relay setting is towards the charging mode
of battery. And in
out circuit the relay in on when the main supply is off and the normally open contacts of
relay is put to inverter operation that discharging operation.

For being achieve this requirement the relay is switched on and of f by using accoci
tate
electronic circuitry which sense the main supply as explained above and main sensing is
compare with referee dc battery signal voltage by using comparator circuits.




































14



BATTERY CHARGING CIRCUIT:
-


When the inverter oper
ation is off and the main an supply I coming the inverter is in
charging mode i.e. the inverter is convert ac into dc and charge the battery. Our
circuit has a completer protection of the battery during charging to prevent any
suphation during charging the

protections are

1.
The battery is cut out from changing when the its full charged

2.
We can control the battery charging current.

3.
The battery is charged at control or continuous regulate voltage by using SCR
circuitry whose gate is trigger by sensing battery
signal the control the charge.

4.
Deep discharge protection of battery


When the circuilt at the charging mode the transformer duty is working to step down
charging dc voltage to the battery through inbuilt diodes of MOSFET.

For ahieve the above said operatio
n, both the ends of the trasformer is connected the
drain terminal of mosfet and we got the positive supply at the center tappin of the
transformer terminal which is connected to the poisitive terminal of battery.

The source of the mosfset is connected to

the negative terminal of the battery through
the .001 ohm sensing resiter. Which sense the battery voltage and current for futher
utilized for processing the and provide the protection .

The circuilt contain IC3 (LM325), IC (MOC3021) and IC(LM34)

With tw
o SCR to provide required control charging current the battery.
























15



CHARGING CONTROLL S.C.R. CIRCUILT:
-









16


COMPONENTS REQUIRMENT :
-