Power flow in the basic series inverter In the basic series inverter circuit (series RLC with commutating capacitor and two SCRs), the DC source supplies the load during which part(s) of the current cycle?

Introduction / Context:
The basic series inverter converts DC to an AC-like current by alternately firing two SCRs, forcing a series RLC circuit to resonate. Understanding when the source actually delivers energy helps in component rating and efficiency analysis.

Given Data / Assumptions:

• Series inverter with DC source, two SCRs (in opposite legs), commutating capacitor, and series RLC load.
• Idealized operation with proper commutation and sustained oscillatory current per half-cycle.

Concept / Approach:
When SCR1 conducts, the source applies one polarity to the RLC, producing a quasi-sinusoidal current (positive half-cycle). When SCR2 conducts, the bridge reverses the applied polarity, and the source again feeds the load (negative half-cycle). Although reactive elements exchange energy, the topology draws energy from the source during both conduction intervals.

Step-by-Step Solution:
Trigger SCR1 → source supplies RLC in one polarity → current rises and decays through resonance.Commutation via the capacitor turns SCR1 off and enables SCR2.Trigger SCR2 → source now supplies in opposite polarity → negative half-cycle load current is produced.

Verification / Alternative check:
Instantaneous input power waveforms show positive power pulses to the load in both half-cycles, despite reactive power cycling within R and C/L.

Why Other Options Are Wrong:
Only positive or only part cycles: Do not reflect the bidirectional application of the DC source via alternate SCRs in a full cycle.

Common Pitfalls:
Confusing energy return intervals (via commutation capacitors) with the absence of source delivery; in practice, each half-cycle involves source contribution when the respective SCR conducts.

Final Answer:
both in positive and negative half cycles