The numbers
of equalizing rings in the DC Generator are = Numbers of armature conductors /
Numbers of pair of poles
What is
meaning of winding has been developed for 100% equalization connection?
If all the armature conductors are connected to the equalizer rings, it is called as 100% equalization connection.
Why the
equalizing connection is not used in the wave wound machines?
Equalization
connection
The
equalizing connection is not used in the wave winding because there are two
parallel paths in the wave winding resulting no unbalance of current in that
path. If there is inequality of flux, they will affect each parallel path
equally.
What is
happened when two DC shunt Generator is parallel with incorrect polarity?
When two DC
Generators are paralleled with incorrect polarity, short circuit occurs. This
will damage brushes and commutator and tripping of the Generators.
What is
meaning of ‘floating’ condition in the two parallel operated DC Shunt
Generator?
Floating
When two
Generators are paralleled with each other, the induced emfs of the both
Generators are same. This will result the current cannot be flow between them.
This condition is known as ‘floating condition’.
How one
Generator is taken out of service in the two parallel operated DC shunt
Generator?
Two
parallel DC shunt generator
The field
of the DC Generator which is taken out of service is weakened and that of the
other Generator is increased till the ammeter of the Generator shows zero. The
circuit breaker and the switch are open thus removing the DC Generator out of
service.
Which
Generator delivers more current than that of other one if the DC Shunt
Generator A has more drooping characteristics than that of DC Shunt Generator
B?
The DC
shunt Generator A delivers less current than that of DC shunt Generator B.
The
parallel operation of two compound Generators is possible or not? Why?
The
parallel operation of the two compound Generators is unstable for constant load
condition.
Let it is
assumed that compound Generator A carries slightly higher load than that of
compound Generator B due to some reason. Due to current passing through series
field winding of compound Generator A, its field strengthens resulting raises the
generated emf. The Generator A takes even more load. The load on the Generator
B drop as the system load is constant. Therefore, the generated emf of the
compound Generator B reduces result further drop in load. This process is
cumulative resulting Generator A will take entire load and Generator B acts as
a motor. The circuit
breaker of one Generator will open. This will result the parallel operation of
the Generator stop.
What is
magnetizing characteristic of the DC Generator?
The
magnetizing characteristics of the DC Generator show the relation between no
load armature emf and field current.
Which type
of DC Generator does not requires equalizing ring for parallel operation?
Under
compound DC Generator
Which
characteristic of DC Generator helps to decide stability for a particular
application?
External
characteristics of DC Generator: Terminal voltage (v) versus load current (I)
Explain:
‘The open circuit characteristics of the self excited Generator is straight
line at low value of flux density’
Open circuit
characteristic
The
reluctance of the iron path is negligible at low value of flux density
resulting the total reluctance is only air gap reluctance which is constant. Therefore,
the generated emf is directly proportional to field current at low value of
flux density.
‘The
generated emf is directly proportional to field current’ comment on above
statement
Generated
emf – Field current
The
generated emf is directly proportional to the field current is true only for
low value of flux density. The value of permeability is small at high value of
flux density therefore the reluctance of the iron path becomes appreciable. Due
to above reason the relation between generated emf and field current is not
straight line.
Is there
any emf is generated at zero field current in the self excited DC Generator?
Some emf is
always generated at zero field current in the self excited DC Generator due to
residual magnetism of poles.
Which
parameter greatly affects the initial slope of the generated emf – field
current?
Air – gap
width
Explain the term: Critical resistance
Critical
resistance
The slope
of the open circuit characteristics of the DC shunt Generator is called as
critical resistance.
Describe
the condition of building up DC Shunt Generator.
Condition
of building up DC Shunt Generator
There must
be some residual magnetism in the poles. The shunt field coil should be
correctly connected to armature coil. The shunt filed resistance should be less
than the critical resistance if it is excited an open circuit.
How to obtain
driving torque in the DC Generator?
The driving
torque is nothing but prime mover therefore it is diesel engine, steam turbine
or water turbine.
What is
direction of rotor and electromagnetic torque in the case of (a) Generator (b)
Motor?
Generator
The
direction of rotor and electromagnetic torque are in the opposite direction.
Motor
The
direction of the rotor and electromagnetic torque are in the same direction.
Why the
electromagnetic torque in the (a) Generator is opposite to that of the rotor
direction. (b) Motor is same as that of direction of the rotor?
Generator
The field
flux in the Generator concentrated at the trailing pole tips whereas it weakens
at leading pole tips so the generated electromagnetic torque is opposite
direction to that of the direction of the rotor.
Motor
The field
flux in the motor concentrated at the leading pole tips whereas it weakens at
trailing pole tips so the generated electromagnetic torque is same direction as
that of the direction of the rotor.
You may also like :
No comments:
Post a Comment