DC Motors
Differentially compound D.C. motors can find applications requiring

Low starting torque
High starting torque
Variable speed
Frequent on-off cycles

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DC Motors
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens

This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
This will make armature to take heavy current, possibly burning it
Motor will run at very slow speed
Nothing will happen to the motor

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