Hello, readers welcome to the new post. In this tutorial, we discuss What is SALIENT POLE THEORY of SYNCHRONOUS MACHINES. Synchronous machines are types of machines that operate at synchronous speed. There are two main types of these machines first one is a synchronous generator and the second one is a synchronous motor.
In this post, we observe the behavior of salient pole theory and its fact at the synchronous machines. So let get started
- The equivalent circuitry of the synchronous generator is operated for machines having a cylindrical rotor not for machines having salient pole rotor.
- Similarly, the expression used for torque and power of generators is worked for the cylindrical rotor.
- The issue to the normal equivalent circuitry for induction motor is that it left the fact of reluctance torque at the generator.
- For an understanding of reluctance, torque see the below diagram having salient pole rotor without zero windings in 3 phase stator
- If the stator field is generated can see in the below figure. it will be generated filed in the rotor.
- It is easy to generate flux about the rotor axis then to create about an axis the flux produced in the rotor will align to the axis of the rotor.
- As the angle between the stator field and rotor field the torque will be produced in the rotor that will align to the field stator.
- The magnitude of torque is proportional to sine of 2θ
EQUIVALENT CIRCUIT OF SALIENT-POLE SYNCHRONOUS GENERATOR
- There are 4 main components sed to make the equivalent circuitry of salient pole synchronous generator.
- Internal Generated Voltage
- Armature reaction
- Self inductance at Stator coil
- Stator winding resistance
- The ist 2nd and 4th components are non varied in the saline pole theory of generator. While armature reaction should be updated to define the behavior which is easy to make flux in a certain direction
- This changing of the armature reaction factor is done through the use of the below diagram.
- The below figure indicates 2 salient pole rotor rotating in an anticlockwise direction in 2 pole stator.
- The rotor flux of this motor known as BR and directed to upward.
- the equation for induced voltage is given here.
- The voltage in the conductor at the top portion of the stator is positively directed outward and voltage in a conductor is less part of the stator in the page.
- The plane of extreme induced voltage exist directed in the rotor pole for a given time
- If lagging or inductive load is linked at points of the generator.in results, current will passes that extreme lies the extreme voltage.
- Figure C- 2b.
- The stator current will generate mmf which lagging ninety degrees to the plane of extreme stator current
- Figure C- 2c
- the MMF generates stator field Bs which is aligned to the stator MMF
- Though it is easy to generate field in direction of rotor which it generates in direction at ninntry degree to rotor.
- So now we parted the stator MMF in elements parallel to ninety degre to rotor.
- Every of these MMF generates field but flux is generated per ampere turn about the axis is generated ninty degrees to the axis
- The resultant stator field can be seen here.
- Here every element of the stator field generating voltages in the stator coil through armature reaction.
- The armature reaction voltages can seen here.
- C- 2e .
- The net voltage stator can be seen here
- In this equation, Ed is a six element of armature reaction voltage and Eq is a quadrate axis element of armature reaction.
- (see Figure C- 3)
- In case of cylindrical rotor observation, every armature reaction voltage is directed proportional to stator current and lagging the ninety degrees of stator current.
- So every armature reaction voltage is given here.
Ed = -jxdId
Eq = -jxqIq
- Voltage about stator is givne here.
Vθ = EA- jxdId – jxqIq
- the armature resistance and self reactance should be added. As armature reaction self reactance XA is not dependent on the angle of rotor.
- The armature reaction resistance voltage loss is like to the armature resistance multiple of armature current IA.
- So total equation for phase voltage in case of salient pole machine is given here.
salinat pole equation
- Observe that the phasor diagram needed the aramture current to solved in elements parallel to the internally generated voltage.
- The angle among the internal generated voltage and armature current is δ+θ