Effect of current chopping in inductive circuits Current chopping (forced current interruption at a non-zero value) primarily causes which transient?

Introduction / Context:
Current chopping occurs when a current in an inductive path is interrupted rapidly before naturally decaying to zero. This is common in circuit breakers and some controlled converters, and understanding the resulting transient is crucial to insulation coordination and snubber design.

Given Data / Assumptions:

• Load includes inductance L, storing energy ½ * L * I^2.
• Interruption is fast compared to the circuit’s natural time constant.
• No ideal clamp present unless stated.

Concept / Approach:
Inductors oppose sudden change in current. For a rapid current drop, the inductor generates a voltage v_L = L * di/dt in whatever polarity is needed to keep current flowing. A large negative di/dt therefore produces a high magnitude voltage spike, risking insulation breakdown unless snubbers, varistors, or free-wheeling paths are provided.

Step-by-Step Solution:
Assume current I is chopped to a smaller value (even to zero) in a short time Δt.Then di/dt ≈ −I/Δt → large magnitude.Induced voltage v_L = L * di/dt → large over-voltage unless clamped.

Verification / Alternative check:
Oscillograms of chopped currents show voltage spikes coincident with interruption. Proper snubbers limit dv/dt and peak v.

Why Other Options Are Wrong:

• Over-current: chopping reduces current; the main risk is voltage rise.
• “Both” or “either”: without a resonant overshoot path, the primary concern is over-voltage.
• “No transient”: contradicts inductor behavior.

Common Pitfalls:

• Underestimating energy ½LI^2 released into stray capacitances, creating high dv/dt.
• Forgetting to add snubbers/free-wheel diodes in inductive paths.

Final Answer:
Over-voltage