V Curve- Excitation vs Armature current
V curve is the graph showing the relation of armature current as a function of field current in synchronous machines. The purpose of the curve is to show the variation in the magnitude of the armature current as the excitation voltage of the machine is varied.
Inverted V Curve- Excitation vs Power Factor
The synchronous motor “V Curves” shown above illustrate the effect of excitation (field amps) on the armature (stator) amps and on system power factor. There are separate “V” Curves for No-Load and Full-Load and sometimes the motor manufacturer publishes curves for 25%, 50%, and 75% load. Note that the Armature Amperage and Power Factor “V” Curves are actually inverted “V’s”.
Assume it is desired to determine the field excitation which will produce unity power factor operation at full motor load. Project across from the unity power factor (100%) operating point on the Y-Axis to the peak of the inverted Power Factor “V” Curve (blue line). From this intersection, project down (red line) from the full-load unity power factor (100%) operating point to determine the required field current on the X-Axis.
In this example the required DC field current is shown to be just over 10 amps. Note at unity power factor operation the armature (stator) full-load amps is at the minimum value.
Increasing the field amps above the value required for unity power factor operation will cause the machine to run with a leading power factor, while field weakening caused the motor power factor to become lagging. When the motor runs either leading or lagging, the armature (stator) amps increases above the unity power factor value.
More Electrical Question
V curve is the graph showing the relation of armature current as a function of field current in synchronous machines. The purpose of the curve is to show the variation in the magnitude of the armature current as the excitation voltage of the machine is varied.
Inverted V Curve- Excitation vs Power Factor
The synchronous motor “V Curves” shown above illustrate the effect of excitation (field amps) on the armature (stator) amps and on system power factor. There are separate “V” Curves for No-Load and Full-Load and sometimes the motor manufacturer publishes curves for 25%, 50%, and 75% load. Note that the Armature Amperage and Power Factor “V” Curves are actually inverted “V’s”.
Assume it is desired to determine the field excitation which will produce unity power factor operation at full motor load. Project across from the unity power factor (100%) operating point on the Y-Axis to the peak of the inverted Power Factor “V” Curve (blue line). From this intersection, project down (red line) from the full-load unity power factor (100%) operating point to determine the required field current on the X-Axis.
In this example the required DC field current is shown to be just over 10 amps. Note at unity power factor operation the armature (stator) full-load amps is at the minimum value.
Increasing the field amps above the value required for unity power factor operation will cause the machine to run with a leading power factor, while field weakening caused the motor power factor to become lagging. When the motor runs either leading or lagging, the armature (stator) amps increases above the unity power factor value.
More Electrical Question
Good Info.
ReplyDeletewhy the unity power factor line ain't linear?
ReplyDeletestil it should be clear to understand for all
ReplyDeleteKiran-what type doubt you have?
ReplyDeleteit is clear and easily understandable
ReplyDeleteThanks :)
ReplyDeleteReally thank U yaar.....Tomorrow I have to submit my assignment and you helped me a lot...
ReplyDeletegood info
ReplyDeletejaffa
ReplyDelete