In Ward-Leonard control the lower limit of speed is imposed by
all of the above
mechanical losses of motor and generator together
core losses of motor
residual magnetism of the generator
residual magnetism of the generator
During rheostat braking of D.C. series motors
motor is reversed in direction
motor is run at reduced speed
motor is run as a generator
None of the above
motor is run as a generator
Which method of braking is generally used in elevators ?
Plugging
None of the above
Rheostatic braking
Regenerative braking
Plugging
In variable speed motor
a weaker commutating field is needed at low speed than at high speed
same commutating field is needed at low speed than at high speed
a stronger commutating field is needed at low speed than at high speed
none of the above is correct
a weaker commutating field is needed at low speed than at high speed
Where D.C. motor of H.P. 12 or more requires frequent starting stopping reversing and speed control
all above can be used
drum type controller is used
three point starter is used
four point starter is used
drum type controller is used
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens
this will make armature to take heavy current possibly burning it
this will result in excessive speed possibly destroying armature due to excessive centrifugal stresses
nothing will happen to motor
motor will come to stop
this will make armature to take heavy current possibly burning it
D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the
any of the above
compound motor
shunt motor
series motor
series motor
Flywheel is used with D.C. compound motor to reduce the peak demand by the motor compound motor will have to be
level compounded
under compounded
cumulatively compounded
differentially compounded
cumulatively compounded
D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this
compound motor
any of the above
shunt motor
series motor
compound motor
Which one of the following is not the function of pole shoes in a D.C. machine ?
To reduce eddy current loss
To spread out flux for better uniformity
To support the field coils
To reduce the reluctance of the magnetic path
To reduce eddy current loss
पोस्ट अच्छी लगी हो तो प्लीज नीचे दिए गए लिंक पर क्लिक कर शेयर जरुर करें
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