Basic Series Inverter : Detailed Working and Output Waveforms

BASIC SERIES INVERTER

Important Features
This inverter uses Class A commutation technique(Self commutation by resonating the load )

The combination of R-L-C form under damped resonance circuit and RLC circuit should be underdamped for Load commutation.

As the SCRs S1 and S2 turn off themselves by natural commutation , it is also called as self commutated inverter.

It is also called as series inverter because in this circuit the inductor and capacitor are connected in series with switching devise that is thyristor.

It is used at high frequencies 200 Hz to 100 KHz.

Used for induction Heating and Fluorescent lightening .

WORKING

MODE -1
We assume that initially VC = - VCO

At switching instant : As I0 = 0 ⇨ VL = VS + VCO

When S1 is triggered
Capacitor starts charging and Load current starts increasing with initial rate of rise of (ⅆ𝐼_0)/ⅆ𝒕
VC = VS + VCO

When I0 reaches peak value ⇨ VL = 0 ⇨ VC = VS

MODE -2
S1 and S2 both are OFF in this mode

Load current I0 = 0 and V0 = I0.R = 0

As capacitor is not getting any path to discharge it self, the voltage across capacitor is maintained as before.
VC = VS + VCO

VL = 0

MODE -3
S2 is F.B due to voltage across capacitor
Load current I0 reverses its direction and
V0 = - I0.R

Capacitor starts discharging and inductor starts absorbing the energy.

As S1 is OFF ⇨ source current IS will not flow

VL = VS + VCO

VC = - VCO

MODE -4
S2 is F.B due to voltage across capacitor
Load current I0 reverses its direction and
V0 = - I0.R
Capacitor starts discharging and inductor starts absorbing the energy.

As S1 is OFF ⇨ source current IS will not flow

VL = VS + VCO

VC = - VCO

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