🔍 Key Concepts

• DC compound motor behavior when shunt field flux is reduced • Relationship between flux, speed, and counter-electromotive force (CEMF) in DC motors • Effect of an open shunt field circuit on motor speed and safety

💭 Think About

• Think about how motor speed must change to keep the balance between applied voltage, armature current, and CEMF when the field flux gets weaker. • Consider what happens to the torque and current draw if the motor tries to maintain load with a much weaker magnetic field. • Ask yourself which response of the motor would be the most dangerous and why protection devices are used on DC motors.

✅ Before You Answer

• Verify whether reducing field flux tends to make a DC motor speed up or slow down. • Check what happens to CEMF when speed changes and how that affects armature current. • Consider whether an open shunt field is a condition that can cause rapid overspeed, requiring emergency protection.