Power plants alternating emf is generated by rotating

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Discussion Overview

The discussion revolves around the generation of alternating electromotive force (emf) in power plants, particularly focusing on the relationship between the angular velocity of turbines and the stability of output frequency and current. Participants explore the challenges of maintaining constant turbine speed, especially in hydro power plants, and the mechanisms that allow for consistent power supply despite variations in load.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the feasibility of maintaining a constant angular velocity of turbines in hydro power plants while supplying a constant rated current.
  • Another participant asserts that the emf generated is independent of turbine speed, noting that turbine speed primarily affects frequency.
  • A participant inquires about how the output frequency is maintained constant despite variations in turbine speed.
  • It is proposed that the grid's constant frequency helps maintain turbine speed, as multiple generators share the load, stabilizing frequency across the system.
  • Concerns are raised about the frequency dropping if a power plant operates independently and the real power demand exceeds supply.
  • One participant mentions that large turbines have significant inertia, making it easier to maintain a stable angular velocity, while smaller turbines may experience speed drops under sudden load changes.
  • Governors on turbines are highlighted as mechanisms that adjust energy input and torque in response to load changes.
  • It is noted that large turbines typically operate on a grid as base load units, while smaller gas turbines serve as peaking units that can quickly ramp up to meet increased demand.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between turbine speed, emf generation, and frequency stability. There is no consensus on the ease of maintaining constant angular velocity or the implications of operating independently from the grid.

Contextual Notes

The discussion includes assumptions about the stability of large turbines versus smaller ones, the role of governors, and the impact of grid connectivity on frequency and power supply. Specific mathematical relationships or definitions are not fully explored.

Who May Find This Useful

This discussion may be of interest to those studying power generation, electrical engineering, or the operational dynamics of power plants, particularly in the context of turbine mechanics and grid stability.

prudhvi mohan
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In power plants alternating emf is generated by rotating loop in magnetic field which is directly proportional to angular velocity of turbine.I think it is highly impossible to maintain angular velocity of turbine constant(especially in hydro power plants).Then how are they supplying a constant rated current?
 
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The EMF generated is independent of the turbine speed, all that turbine speed gives is frequency.
 


but then how output frequency is held constant ?
 


The grids constant frequency keeps turbine speed constant independent of torque on the tubine. 1000+ other generators share the same load and thus keeps a stable frequency.

If the power plant is not connected to a "infinite bus/grid" but operating alone, the frequency will drop if demanded real power exceeds supplied power.

Keeping a constant angular velocity (within acceptable limits) isn't that hard, big machines with large inertia is pretty stable. Small machines with less inertia can for a few seconds have a speed drop if a sudden power demand is connected. Hydro electric plants are ideal for this, since they can regulate the governor setpoint pretty fast, steam turbines on the other hand have slower regulator speed.
 


prudhvi mohan said:
In power plants alternating emf is generated by rotating loop in magnetic field which is directly proportional to angular velocity of turbine.I think it is highly impossible to maintain angular velocity of turbine constant(especially in hydro power plants).Then how are they supplying a constant rated current?
Turbines have governors to adjust the input of energy/torque according to the load.

Large turbines are usually base loaded on a grid, which as smaller gas turbines are used as peaking units because they are ramped up quickly in response to increased load.
 

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