Question

D1 ŚW, D2 R4 8200 1N4007 INYOO4 R2 3300 360KN 4 5 6 14 Rs 2200 10 W IRF540 CA MOVI R100KO RDN240 VOUT R6 2200 11 W- CT T2 CD4047 0.1pF 2.2uF 120 2200pF IRF540 13- N.C. 9. 12 0.01pF 13DL10 Figure 1

what is the whole working of this circuit and the purpose of each component??
what is metal oxide varistor and its purpose in this circuit??
how is changing the R1 will change the frequency of generated sine wave??

Answer 1

Purpose of each component:

C1: Stabilized power supply, and you don’t have a resistor in serial with the capacitor it could even be the electronic current limiter that triggers due to the spike.

C2, R1, R1: this resistor and capacitor is used to decide the switching frequency. Describe below in working.

R3, R4 : current limiting resistor connected to IC and LED respectively.

D1: diode D1 protect from reverse power flow

R5, R6: current limiting resistor connected in series with gate pulse of mosfet

T1, T2: switching mosfet

C3, C4: It is used to smooth the output voltage.

RDN240: varistor used to protect from transients

Working:

1. As the switch SW1 is closed power is supplied to IC CD4047 and LED light get turn ON it indicate inverter is ON. CD4047 work in Astable mode

Astable operation is enabled by a high level on the ASTABLE input or a low level on the ASTABLE input, or both. The period of the square wave at the Q and Q Outputs in this mode of operation is a function of the external components employed. “True” input pulses on the ASTABLE input or “Complement” pulses on the ASTABLE input allow the circuit to be used as a gatable multivibrator.

2. This triggering pulses is fed to power switching mosfet through 220 ohm resistor connected in series. Both mosfet operate complementary to each other. First mosfet conduct 0 to 180 degree and then second mosfet conduct 180 to 360 degree.
3. Switching of mosfet generate the square wave ouput which is fed to the step up transformer It step up voltage to supply voltage of our house (110v). Inductance of transformer smooth and parallel connected capacitor across secondary of transformer smoothed the ripple and makes output voltage more sinusoidal.
4. By varying the R1 Resistor value we can change the frequency and voltage range of output AC supply

The formula for calculating the frequency or the RC components are:

f = 1/8.8R1C2 at pin#10 and pin#11

f = 1/4.4R1C2 at pin#13

Where f is in Hz, R in Ohms and C in Farads.

Pulse time may be obtained by solving:

t = 2.48RC    where t is in seconds, R in Ohms and C in Farads

metal oxide varistor and its purpose:

Generaly due high frequency switching power electronic devices misbehave something ( transients in the circuit). This transient contain voltage spikes harmonics component at output of inverter.

To reduced the transients of inverter Varistor is connected acrass the output of inverter transformer. Spikes are shorted through the device within nanoseconds by varistor