What is an induction generator? An induction generator is a rotating electrical machine that produces power without the use of slip rings. It does this by producing a rotating field that induces currents in the rotor windings.
The currents in the rotor windings produce a torque on the shaft that drives the generator.
Similar stator winding configurations on both synchronous and induction generators allow them to be powered by rotating magnetic fields and provide three-phase (or single-phase) voltage outputs.
The rotors of these two machines, however, are very different from one another since an induction generator’s rotor normally has one of two configurations: a “squirrel cage” or a “wound rotor.”
Because it is inexpensive, reliable, and easily accessible in a wide range of electrical sizes from partial horsepower machines to multi-megawatt capacities, the construction of an induction generator is based on a very popular squirrel-cage induction motor type machine, making them ideal for use in both commercial and domestic renewable energy wind power applications.
The induction generator may be linked directly to the utility grid and is immediately powered by the turbines’ rotor blades at variable wind speeds, in contrast to the synchronous generator, which must be “synchronized” with the electrical grid before it can generate electricity.
Many wind power turbines employ induction motors to increase the efficiency, performance, and dependability of their generators while lowering the cost and reliability of the system.
The induction machine is also known as an “Asynchronous Machines,” meaning that when used as a motor, it rotates below synchronous speed and as a generator, it rotates above synchronous speed.
Thus, an induction generator generates AC power when rotated more quickly than its typical working or no-load speed.
No rectifiers or inverters are required since an induction generator produces energy at the same frequency and voltage as the primary utility grid, synchronizing with it directly.
The main utility grid receives the necessary power from the IG directly, but the utility grid’s power supply must be made reactive.
It is also feasible for an induction generator to operate independently or off the grid, but this has the drawback that additional capacitors must be attached to the generator’s windings in order for it to self-excite.
The three-phase induction machines, however, are excellent choices for producing hydroelectricity and even wind energy.
When used as generators, these induction machines feature a fixed stator and a rotating rotor similar to synchronous generators.
A classic rotor design is the squirrel-cage construction, where conducting bars are mounted within the rotor’s body and then they are joined to one another at their ends by shorting rings as illustrated. This method is used to create the rotor’s magnetic field.
The Construction of Induction Generators
As was already indicated, one of the key benefits of an asynchronous machine is that it may function as a generator without the need for any additional wiring and that when linked to a three-phase mains supply, it provides the greatest voltage control.
However, when an idle asynchronous generator is linked to an alternating current grid, the frequency of the induced voltage, which is equal to the frequency of the applied voltage, will be inducted into the rotor winding as to a transformer.
But when the conducting bars in the squirrel cage rotors are short-circuited together, a magnetic field is produced inside the rotor, which causes the machine to revolve.
While doing so, the magnetic field of the rotor cage follows that of the stator and increases in speed until it reaches the synchronous speed determined by the frequency of the grid supply.
The relative speed difference between the spinning stator field and the rotor cage will therefore be less the quicker the rotor turns; as a consequence, the voltage will be induced in the revolving stator field’s winding.
Even though the rotor rotates considerably more slowly than the specified synchronous speed, this will occur when it reaches the synchronous speed and becomes sluggish because the magnetic field around the rotor is insufficient, which causes the rotor to lose friction when it is in idle mode.
Here, it is evident that an induction machine would never reach its synchronous speed range because, if it did, there would be no current to feed into the rotor’s squirrel cage and no torque to cause the magnetic field to lose strength.
The revolving magnetic fields of the rotor and the stator have different rational speeds. Induction machines frequently refer to this as “slip.” For the torque to occur at the rotor shaft, slip is essential.
- nS = f/p (difference in speed between stators synchronous speed)
- nR = (rotors real speed in rpm)
- S = an induction machine’s fractional slips.
The induction machine’s fractional slip is thus stated as: S =(nS-nR)/S
The asynchronous nature of induction generator operation is shown by the aforementioned slip.
When the load connected to the asynchronous generator is heavier, it is also referred to as the slip; this is because the much larger loads require much stronger magnetic fields.
It follows that the operating speeds of induction motors must never be forced to synchronous speed.
While the asynchronous speed should never be more than the induction generators’ speeds.
How Does an Induction Generator Work in Wind Turbines?
An induction generator is a type of electrical generator that is used in wind turbines.
It is a three-phase machine that uses the interaction between a magnetic field and a current-carrying conductor to generate power.
The induction generator typically consists of two parts: a rotor and a stator.
The Rotor:
The rotor looks like a hollow cylinder. It is the moving part of the circuit.
The rotor is attached to the wind turbine and it contains the magnets.
It often has many copper or aluminium bars connecting the two ends of an aluminium ring at each end.
The Stator:
The stator is stationary and it contains the windings that produce the magnetic field.
When the wind turbine starts rotating, the rotor begins to spin around the stator.
This causes the magnets to move past the windings and create a current. This current is then used to generate power.
Working of Induction Generator
Electrical current is fed into the stator, creating a magnetic field inside the armature coils. At this point, the generator begins to function as a motor and pulls the rotor along behind it.
Blades of the wind turbine create kinetic energy, due to which the rotor and the magnetic field in the stator also start to rotate.
Inside the armature coils, this revolving magnetic field produces an alternating electromagnetic force (EMF).
The electrons inside the coils are disturbed by the varying magnetic field, which causes them to constantly change orientations. At this time, the machine starts to produce electricity.
The alternating current is finally sent from the armature coils to the grid and then via transmission lines to the electrical outlets in buildings.
Benefits of Using Induction Generators in Wind Turbines
Wind turbines are a great way to produce renewable energy, and many wind farms are starting to use induction generators.
Here are three benefits of using induction generators in wind turbines:
- Induction generators are more efficient than other types of generators.
- They are more reliable and have a longer lifespan.
- They are quieter and cause less vibration than other types of generators.
Advantages and Disadvantages of Using Induction Generators
As with all types of generators, there are advantages and drawbacks to using induction generators.
Advantages
- On the plus side, these generators are known to be reliable and cost-effective, making them a great choice for many applications.
- They are also easy to maintain and have few moving parts, so they don’t require much in the way of maintenance.
- Furthermore, it has a compact footprint per kW of output power, which leads to high energy density.
Disadvantages
The induction generator has been used in wind turbines for a number of years now. However, there are a few disadvantages to using this type of generator.
- On the downside, induction generators can be less efficient than other types of generators due to their lower rotor speed, which can result in higher losses from copper and iron.
- Additionally, they do not have a self-starting capability, meaning that they need some form of external energy sources like an energy storage system, or an additional generator for a start-up.
- The induction generator needs to be connected to the grid in order to function. If there is an issue with the grid, such as a power outage, the wind turbine will stop working. This can be a problem if you are relying on the turbine to generate power for your home or business.
How to Maintain and Troubleshoot Induction Generator Systems in Wind Turbines
When you’re looking to purchase or maintain an induction generator system in your wind turbine, it’s important to be aware of the different factors that can affect its performance.
Here are a few tips on how to troubleshoot and maintain your system:
- Be sure to keep the generator and its components clean. This will help reduce the amount of wear and tear on the system and improve its performance.
- Check the wiring and connections regularly, and fix any problems as soon as you can. This will help avoid any electrical problems down the road.
- Make sure you have a good supply of spare parts on hand, in case of any unforeseen issues.
- Regularly monitor the system for any signs of trouble, and take corrective action as soon as possible.
By following these simple tips, you can help ensure that your induction generator system remains in good working order and that your wind turbine continues to generate renewable energy for your home or business.
Examples of Induction Generators Used in Wind Turbines
There are several types of generators used in wind turbines, and induction generators are some of the most widely used ones. But why?
Well, induction generators have a number of advantages that make them great for this application, such as being lightweight, efficient, and easy to maintain.
Not only that but they can also be used in situations with varying speeds and torque.
That’s because they don’t require exact mechanical synchronization to operate—which means they don’t need complex control systems or external components like gears or belts.
This makes it easier to install them in a variety of environments.
In addition, induction generators can be designed to convert mechanical energy more efficiently than other types of machines—which is why many manufacturers use them when building wind turbines.
They’re also highly reliable and can operate for a long time without needing repairs or maintenance.
