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1. In a synchronous generator, the waveform of the generated voltage is synchronized and directly corresponds to the rotor speed. Separate DC excitation system is required in an alternator or synchronous generator while an Induction generator takes reactive power from the power system for field excitation.1. In a
Permanent magnet synchronous generator – Wikipedia
, the waveform of the generated voltage is synchronized and directly corresponds to the rotor speed. Separate DC excitation system is required in an alternator or synchronous generator while an Induction generator takes reactive power from the power system for field excitation.
What is difference between induction generator and synchronous generator?
An induction generator produces electrical power when its rotor is turned faster than the synchronous speed. The motor normally turns slightly slower than the synchronous speed; the difference between synchronous and operating speed is called “slip” and is usually expressed as per cent of the synchronous speed.
What is the difference between synchronous and asynchronous generator?
A synchronous generator is called “synchronous” because the waveform of the generated voltage is synchronized with the rotation of the generator. An asynchronous generator is essentially the same machine as an asynchronous or induction motor.
What is the difference between synchronous and induction machine?
The electromagnetic motor which converts electrical energy into mechanical work at variable speed is called as a ‘Induction Motor’. Synchronous motor runs at the synchronous speed. Induction motor runs at the non-synchronous speed. The synchronous motor works on the principle of the ‘Magnetic Locking’.
What is meant by synchronous generator?
[′siŋ·krə·nəs ′jen·ə‚rād·ər] (electricity) A machine that generates an alternating voltage when its armature or field is rotated by a motor, an engine, or other means. The output frequency is exactly proportional to the speed at which the generator is driven.
What is the principle of synchronous generator?
The principle of operation of synchronous generator is electromagnetic induction. If there exits a relative motion between the flux and conductors, then an emf is induced in the conductors.
Why capacitor is used in induction generator?
The function of the capacitor bank is to provide the lagging reactive power to the induction generator as well as load. There is generation of small terminal voltage oa (as in figure given below) across the stator terminal due the residual magnetism when the rotor of the induction machine runs at the required speed.
Why synchronous motors are not self starting?
Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator. Once the rotor nears the synchronous speed, the field winding is excited, and the motor pulls into synchronization.
Why do we use synchronous generator?
Synchronous generators are the majority source of commercial electrical energy. They are commonly used to convert the mechanical power output of steam turbines, gas turbines, reciprocating engines and hydro turbines into electrical power for the grid. The load supplied by the generator determines the voltage.
What are the two types of synchronous generators?
Types of synchronous machines Hydrogenerators : The generators which are driven by hydraulic turbines are called hydrogenerators. These are run at lower speeds less than 1000 rpm. Turbogenerators: These are the generators driven by steam turbines. Engine driven Generators: These are driven by IC engines.
What is the main disadvantage of synchronous motors?
Disadvantages or Demerits: Synchronous motors requires dc excitation which must be supplied from external sources. Synchronous motors are inherently not self starting motors and needs some arrangement for its starting and synchronizing. The cost per kW output is generally higher than that of induction motors.
Why it is called induction motor?
This type of engine is also known as an induction motor. The asynchronous motor is based on the currents induced in the rotor from the rotating magnetic field of the stator. That’s why it’s called an induction machine.
What are the types of induction generator?
Generally, there are two types of induction generators widely used in wind power systems – Squirrel-Cage Induction Generator (SCIG) and Doubly-Fed Induction Generator (DFIG).
Why is excitation always DC?
To keep it short we can conclude that to get steady state torque and to synchronize the rotor we use dc excitation. If you use AC excitation, flux will be alternating. For dynamically induced emf, you need a constant flux (provided by DC excitation) and a rotating coil. This is the basic principle of DC/AC generator.
Where are synchronous generators used?
Synchronous generators are commonly used for variable speed wind-turbine applications, due to their low rotational synchronous speeds that produce the voltage at grid frequency. Synchronous generators can be an appropriate selection for variable speed operation of wind turbines [166,167].
How does a synchronous generator start?
In a synchronous generator, a DC current is applied to the rotor winding producing a rotor magnetic field. The rotor is then turned by external means producing a rotating magnetic field, which induces a 3-phase voltage within the stator winding. The rotor of a synchronous machine is a large electromagnet.
What is a 3 phase synchronous generator?
A three-phase synchronous machine consists of an inner rotating cylinder called the rotor and an outer stationary housing called the stator as shown in Figure 5.2. A shaft runs through the rotor and it is balanced on bearings.
Can a synchronous motor be used as a generator?
Figure 1 shows a cross-sectional view of a salient-pole synchronous machine. The armature windings are shown as concentrated windings, but in reality, they would be distributed. Such machines can be operated either in Motor or Generator mode.
Is alternator a synchronous generator?
Since the currents in the stator windings vary in step with the position of the rotor, an alternator is a synchronous generator. The rotor’s magnetic field may be produced by permanent magnets, or by a field coil electromagnet. Brushless AC generators are usually larger than those used in automotive applications.
What are the limitations of induction generator?
The principal disadvantages of an induction generator are listed below It is not suitable for separate, isolated operation. It consumes rather than supplies magnetizing KVAR. It cannot contribute to the maintenance of system voltage levels (this is left entirely to the synchronous generators or capacitors).
What is the power factor of induction generator?
in most induction generator applications, power factor correction in the form of capacitance will be required to raise the induction generator’s operating power factor up to the area of 0.90 to 0.95 lagging. (Power factor correction information is available from companies that sup- ply industrial capacitor banks.).
Is it necessary to use capacitor banks in induction generator?
The capacitors deliver reactive power to the stator windings making it able to set up a magnetic field. This magnetic field induces a voltage and hence a current in the rotor making voltage build up in stator windings. Without the capacitors the stator windings could never induce a magnetic field.
