As shown in figure "A" of the illustration,...

🔍 Key Concepts

• Ward-Leonard (M-G set) DC motor control – which part of the system actually changes to vary speed? • Relationship of DC motor speed to armature voltage and field flux (field voltage/current):

N \propto V_{arm} / \phi

. • In the figure, note which winding has the labeled Speed Control device and which winding is fed from the Field Rectifier without an adjustable element.

💭 Think About

• Trace the circuit from the speed control symbol in figure A: does it end up affecting the generator/armature circuit or the motor field circuit? • Ask yourself: if the field rectifier output goes directly to a field winding with no variable resistor in series, is that field being kept essentially constant or varied for speed control? • Use the DC motor speed formula: if one of the two factors (armature voltage or field flux) is clearly being adjusted in the drawing, what does that imply about the other factor during speed control?

✅ Before You Answer

• Identify exactly which coil in figure A is the motor field and how it is supplied from the Field Rectifier. • Confirm whether the Speed Control device is wired in the generator field/armature supply path or in the motor field circuit. • Decide, based on the wiring, which quantity is held essentially constant during normal speed control: armature voltage or field voltage.

As shown in figure "A" of the illustration, by what means is the DC motor speed controlled? See illustration EL-0101.

by varying the applied armature voltage and maintaining a constant applied field voltage

by varying the applied armature voltage and varying the applied field voltage

by maintaining a constant applied armature voltage and varying the applied field voltage

by maintaining a constant applied armature voltage and maintaining a constant applied field voltage

🔍 Key Concepts

N \propto V_{arm} / \phi

. • In the figure, note which winding has the labeled Speed Control device and which winding is fed from the Field Rectifier without an adjustable element.

💭 Think About

✅ Before You Answer