Disadvantages and Limitations of basic Series Inverter
Limitation on the maximum operating frequency :
- The maximum frequency of operation is restricted to the resonant frequency of the resonant circuit formed by commutating components.
Fmax = 1 / 2
π √L1C1
- This is because SCR2 can be turned on only after SCR1; is turned off otherwise there will be a short circuit on the input power supply.
- Distortion in the output waveform :For the output frequency much less than the resonant frequency the distortion in the load voltage waveform is high as the off time is larger than on time.
(The ON time is fixed = 2 π √L1C1
* to vary frequency the off time has to be varied).
- High rating of commutating components :As the commutating components have to carry the load current continuously and the capacitor has to supply the load current for one half cycle, the ratings of L1, and C1, are high.
- The peak amplitude and duration of output current depends on the load resulting in poor regulation for the inverter.Therefore the dc supply must have a large peak current rating and the input current contains a high percentage
- The power flow from the dc source is intermittent. Therefore the dc supply must have a large peak current rating and the input current contains a high percentage of harmonics.