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Worksheetselectrical machine lab
Total questions: 15
Worksheet time: 15mins
- In DC motor speeds above the rated speed are usually increased by changing which of the following winding current:
field winding
armature winding
either field or armature winding
none of these
In DC generator which of the following device plays an important role to provide dc current:
brushes
commutator
equalizer colis
dummy coils
The direction of rotation of DC series motor can be reversed by interchanging which terminals:
Armature
supply
either armature or field
field
Starter is used in DC motor for which of the following purpose:
improving back emf
improving starting torque
improving efficiency
reducing starting current
Which of the following DC Motor is best suited for speed control applications such as in rolling mills and paper mills:
DC shunt motor
DC series motor
DC compound motor
DC differential compound motor
Armature of the dc machine is laminated to reduce which of the following:
hysteresis loss
eddy current loss
both eddy current loss and hysteresis loss
copper loss
The rotating part of the dc machine is known as:
rotor
field
armature
stator
The current flowing through the armature of the dc motor is:
none of these
pulsating
DC
AC
The main advantage of dc motors compared to ac motors are:
high starting torque
frequency control
less maintenance
low cost
The power rating that is indicated on name plate of any motor is:
gross power
output power of shaft
power drawn in kVA
net power
Which type of power supply is given to Generator Field winding:
pulsating DC supply
AC supply
DC supply
none of these
If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be:
the same as rated voltage
low
high
zero
For what type of applications the lap winding is used in DC generators:
high current applications
high power applications
high voltage applications
high frequency applications
The armature core is mounted on ……………… of the DC generator:
slots
shaft
yoke
pole shoe
A 120 V DC Generator is run at full speed without any excitation. The open circuit voltage will be:
about 15V
zero
about 1V
120V
