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

Armature voltage control
Mechanical loading system
Field control
Shunt armature control

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DC Motors
If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor

Of higher H.P. should be selected
Of lower H.P. should be selected
Can be used for 50°C ambient temperature also
Is to be de-rated by a factor recommended by manufacturer and select the next higher H.P. motor

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