What are the OCC characteristics of dc generator?
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What are the OCC characteristics of dc generator?
driven at rated speed. Because of presence of small residual flux in the field poles, DC Shunt Generator will have a small voltage at its terminal even though the switch S is open when driven at rated speed. Now suppose the switch S is closed.
Why the OCC of DC shunt generator not starts from the origin?
The curve does not start from the origin but from the point above the Y-axis, slightly above the origin. This is due to the residual magnetism in the poles of generator at low value of field current. draw the O.C.C. at any other constant speed N2.
How do you find critical field resistance from OCC?
The steps are,
- Drawn O.C.C. for given speed N1.
- Draw a line tangential to this O.C.C. say OA.
- Draw a line representing the given Rsh say OP.
- Select any field current say point R.
- Draw vertical line from R to intersect OA at S and OP at T.
- Then the critical speed NC is,
How do you calculate critical speed from OCC?
Draw the given O.C.C and a line tangent to O.C.C. Draw a line ordinate intersecting the field resistance line and a tangent to O.C.C. Multiply the speed by the ratio of intercepts of ordinate drawn between field resistance line and the tangent line to O.C.C. Thus, the result will be the critical speed.
What is shunt wound motor?
shunt-wound in Electrical Engineering A shunt-wound motor or generator has the field and armature circuits connected in parallel. Current in the field windings of a shunt-wound generator is independent of the load current, because currents in parallel branches are independent of each other.
Why it is called OCC of the alternator?
With the armature terminals open, Ia=0, so Eg = Vt It is thus possible to construct a plot of Eg or Vt vs If graph. This plot is called open-circuit characteristic (OCC) of a generator. With this characteristic, it is possible to find the internal generated voltage of the generator for any given field current.
What is critical field resistance of DC shunt generator?
The critical field resistance is defined as the maximum field circuit resistance (for a given speed) with which the shunt generator would just excite. The shunt generator will build up voltage only if field circuit resistance is less than critical field resistance.
What are shunt DC motors?
A DC shunt motor (also known as a shunt wound DC motor) is a type of self-excited DC motor where the field windings are shunted to or are connected in parallel to the armature winding of the motor. Since they are connected in parallel, the armature and field windings are exposed to the same supply voltage.