The Speed Of Rotation On Electric Machines

The Speed Of Rotation On Electric Machines

Synchronous generators are by definition synchronous,  meaning that the electrical frequency produced is locked in or synchronous with the mechanical rate of rotation or the generator.

The rate or rotation of the magnetic field 

nsyn = ns = ( 120 * fc ) / p

fc → electrical frequency, in Hz

nsyn → ns → synchronous speed, rpm

p → H of poles

if the speed of rotor n, for synchronous machine 

nsyn = ns = nm

The Internal Generated Voltage 

The magnitude of the voltage induced in a give stator phase 

Ea = 2 * 𝜋 * Nc * ⲫ * f

Ea = K * ⲫ * ⍹ 

if ⍹  is expressed in electrical radians per second 

K = Nc /2 

if ⍹ is expressed in mechanical radians per second

K = Nc * p /2 

The Speed Of Rotation On Electric Machines, Magnetization curve or open circuit characteristics of the machine
Magnetization curve or open circuit characteristics of the machine

The Equivalent circuit of a synchronous generator 

Ea is the internet generates voltage 

Vⲫ is the terminal voltage of the generator 
There are a number of factors that cause the difference between Ea and Vⲫ

  1. The distortion of the air gap magnetic field by the current flowing in the stator, called armature reaction – AR 
  2. The self inductance of the armature coils 
  3. The resistance of the armature coils 
  4. The effect of salient pole rotor shapes 

Vⲫ = Ea – jXs*Ia – Ra*Ia

Ra -> winding resistance 

Xs -> synchronous reactance

Xs = XAR + XAl 

XAR → inductance due to AR

XAl →self inductance 

The Speed Of Rotation On Electric Machines

The Speed Of Rotation On Electric Machines, The lull  equivalent circuit of a three phase synchronous generator
The lull  equivalent circuit of a three phase synchronous generator

there phase can be either  Y – Δ

Y → VTLL = 3 *Vⲫ

Δ → VTLL = Vⲫ

SYNCHRONOUS GENERATORS ON ELECTRİC MACHİNES

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