🔍 Key Concepts

• Look at where the AC/DC thyristor controller connects in figure B compared with the old M‑G set in figure A. • Think about whether it is supplying the armature circuit or the field circuit of the DC motor. • Recall that an inverter changes DC to AC, while a rectifier changes AC to DC.

💭 Think About

• In figure B, trace the wiring from the 3‑phase supply through the controller to the DC motor: which part of the motor does it feed? • Which of the answer choices best describes a controlled rectifier that varies the DC voltage to control motor speed? • If there is already a separate "field rectifier" labeled in the diagram, would the thyristor controller also be called a field rectifier, or something else?

✅ Before You Answer

• Verify which device in the illustration is labeled Field Rectifier and which is labeled AC/DC Thyristor Controller. • Confirm that the controller’s output goes to the motor armature terminals, not the field winding. • Eliminate any option whose function is to convert DC to AC rather than AC to DC.