DC Motors
For constant torque drive which speed control method is preferred?

Shunt armature control
Armature voltage control
Field control
Mechanical loading system

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DC Motors
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens

Motor will come to stop
This will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
Nothing will happen to motor
This will make armature to take heavy current, possibly burning it

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