Type B Chopper | Power Electronics | Lecture 70

Understanding Type B Chopper Circuits

Overview of Type B Chopper

• The video introduces the concept of a Type B Chopper, emphasizing its application in realistic scenarios involving RLE loads, particularly with DC motors that exhibit resistance, inductance, and back EMF.

Energy Flow in Type B Chopper

• In a Type B Chopper, energy is transferred from the load (motor acting as a generator) back to the source. This unique operation is crucial for understanding how power flows in this circuit configuration.

Operation During Turn On

• When the chopper is energized by a gate pulse, it acts as a short circuit. The back EMF from the motor influences current flow direction and results in an output voltage of zero due to short-circuit conditions.

Current Direction and Voltage Observations

• The output voltage remains at zero while current flows negatively through the load. This indicates that when current moves away from the load, it is considered negative based on conventional definitions.

Behavior During Turn Off

• During turn-off periods, inductors resist sudden changes in current. They reverse polarity to maintain current flow direction while allowing back EMF to supply power to the load.

Output Voltage Dynamics

• The output voltage during operation can be expressed as V_out = e + V_L (back EMF plus voltage across the inductor), indicating that it remains positive or zero throughout operation.

Waveform Analysis

• Analyzing waveforms reveals that during T_on (turn-on period), output voltage starts at zero and then rises to e + V_L when turned off. This creates a square wave pattern above source voltage levels.

Current Flow Characteristics

• The load current consistently flows negatively from load to source. Initially discharging through resistor R during T_on leads into charging phases where inductors increase their stored energy.

Importance of Type B Chopper Configuration

• A key takeaway is that this configuration allows motors to operate solely as generators under specific conditions, effectively converting mechanical energy into electrical energy within forward braking mode.

Conclusion and Further Engagement

• The video concludes by inviting viewers to ask questions about Type B Choppers and encourages engagement through likes and subscriptions for further updates on related topics.