If you can't explain it simply, then you don't know it well enough. — Albert Einstein


Why inverter generators are quiet compared to normal generators

From many of the generator types in the market, most household owners prefer to use either conventional generators or portable inverter generators. There are many benefits of choosing inverter generators over others, but in between them, the major difference is the noise.

Inverter generators are quieter than conventional generators, but why? even though they have the same fossil fuel engine to generate the power. The answer to that question is the difference in their design parameters as well as in their working mechanisms.

Keep reading to know the reasons for the noise from the generators in the first place and how the design and the working of inverter generators are advantageous to reduce the noise level of the generator.

Why do generators produce noise in the first place?

The answer to that question is because it involves the rotating and moving mechanical parts, which are the main reason for the noise.

The main part of any generator is the engine. The engine runs by burning the fuel, which transfers the power to the pistons inside the engines, which will be responsible for a rotational motion inside the alternator, and the electricity is generated.

The burning of fuel inside the engine are small explosions that make the most of the noise. Companies take some measures to reduce it to some extent, but they can’t totally diminish it, and the matter gets worse when the generator is an open frame generator.

Moreover, a generator will need to maintain a constant speed of 3600 RPM to keep the supply frequency to 60 Hz. And for that, the engine constantly runs and burns the same amount of fuel to maintain that speed to maintain the frequency.

Besides the internal combustion engine, the friction between the moving parts also produces a significant amount of noise.

Why are Inverter generators so quiet?

inverter generator

There are many differences between the conventional generator and the inverter generator in terms of their design and working. It makes the inverter generator quieter.

The first thing is the engine; the engine used in the inverter generators is smaller and a bit quieter than those used in conventional generators. Besides, they don’t need to run continuously to maintain the frequency of the output voltage.

how inverter generator works

The working of the inverter generator ensures the constant frequency. The engine runs the alternator to generate the AC electricity, which is converted to DC and then again AC. The whole process is controlled with the help of a microprocessor.

When the load is less, the microcontroller will reduce the speed of the engine, and so the noise is also reduced, while the frequency remains the same.

The reduced noise is one of the biggest points of inverter generators. All the inverter generators are equipped with advanced noise-reducing technologies and very good mufflers.

Other than that, the casing made out for the generator is from the noise absorbing and quality material.

Can conventional generators be as quiet as inverter generators?

No, you can’t make the conventional generators as quiet as the inverter generators. There are major differences in their working mechanisms, as we discussed.

Still, you can reduce the noise of the conventional generator to quite an extent with the use of some external means, but it will be more than the inverter generators.

Even if you enclose the whole generator in the casing, then you will need the air vents and the exhaust vents. And simply stating, exhaust pipes are the second most noisy part of the generator.


Inverter generators are the best option in the market in terms of noise level and portability. They run very smoothly and offer fuel economy. The engines designed for the inverter generators are inherently quieter than for the conventional generators. Moreover, they are equipped with other accessories to reduce the noise even more.

They are best for home use and for camping use as well. Their initial prices are high, but you get the power with the silence so you can enjoy nature.


Difference between Generators and Alternators

The terms alternator and generator will sound the same to you if you are not a technical person. But, let me tell you, they are not. They are different machines despite the fact that both of them have the same function, to generate useful electricity.

If you want to know what an alternator and generator, how they work, and their differences then we have all of that in this post.

Before we begin, just understand that electricity and magnetism are both related. You can produce one with the help of the other one.

You can produce electricity either by rotating the conductor inside the static magnetic field or by rotating the magnetic field around the static conductor.

Both alternator and generator use these principles to generate electricity.

How an Alternator Works?

alternator or synchronous generator

The alternator is also known as a synchronous generator. Whether it is a generator or an alternator, the fundamental principle to generate electricity remains the same. They both work on the principle of faraday’s law of electromagnetic induction.

The law states that a relative motion between the magnetic field and the conductor will generate the electricity in the conductor.

The same goes for the alternator as well, but unlike generators, it will only give out the AC electricity. The construction of an alternator is simple; the rotor contains the exciting winding, whereas the stator will have the armature winding.

The rotor is the one that rotates, and the exciting winding generates the magnetic field. So, a magnetic field in the alternator rotates while the armature winding stays stationary. An armature winding is a term used to denote the winding in which the electricity is induced.

The reason for the armature winding to be stationary is few. First, the voltage induced in alternators will be higher, so the insulation will be much easier compared to the rotating winding.

Also, If the armature winding will be on the rotor, then there will be a high voltage drop at the brushes, and also, there will be a problem of sparking.

The excitation winding is powered by the DC, and it will be easier to connect the current through the brushes if the winding is on the rotor.

The alternator is a device that generates AC electricity from mechanical energy, and they only provide this energy when it is needed so the operation will be efficient.

How a Generator Works?

generator construction

The generator also works on the same principle of Faraday's law of electromagnetic induction. The alternator only supplies the AC electricity, but the generator provides the DC or AC electricity.

For a generator, the placement of the armature and the excitation winding is opposite to the alternator. The armature winding is situated on the rotor, and the excitation winding is on the stator.

The electricity gets induced in the armature winding on the rotor. On the stator, for magnetic flux, it will either be the permanent magnets or windings are used. The armature winding will be rectangular, and both of its ends will terminate to the brushes.

The rotor inside the generator will rotate with the help of some external mechanical force, and the electricity will get induced in the windings. It will be taken out from the brushes.

The generators produce electricity continuously. It can also be used to recharge the completely drained batteries when they are completely drained, without any problems. Their ability to generate constant power makes them a strong choice as home backup solutions or to power the power tools at the job site.

DC and AC electricity: What is it?

ac and dc electricity

We know that the generator can supply the AC or DC electricity, whereas the alternator can only supply the AC electricity. In this section, let’s discuss what AC and DC electricity are.

AC electricity

You may be knowing that the flow of electrons inside the conductor is referred to as the electric current.

For AC electricity, the flow of electrons will be back and forth, and this means the current is alternating in nature. This is the type of current most of the appliances in the house works on. But the voltage and the frequency of the electricity should be as per the standards.

This periodic change in the current direction is demonstrated in the form of the sine waveform, which is also known as the AC waveform.

The reason for this kind of power generator is because of the magnetic poles inside the generator and alternator. When one side of winding passes from under one of the poles, the electric current will be in one direction.

When the same side comes under another pole, the direction of the current reverses, this keeps going on as the winding keeps rotating and the AC is generated.

DC electricity

The DC means the Direct Current. The DC is the one in which the flow of electrons will be only in one direction. And the magnitude of the current stays the same; it doesn’t change with time.

As there is no oscillation, we can say that the frequency of the DC is zero. The use of DC is mainly to power electronics due to its constant flow of electrons.

The generated current inside the alternator or the generator will always be AC, and you can’t generate DC from them. This AC for the generator is converted to DC with the use of either the brushes or the rectifier.

The process of conversion of AC to DC is known as rectification.

Key Differences between the generator and an alternator

Please note that the alternators used in cars are different from the alternators (also known as a synchronous generator), which are used in a power station to produce electricity in bulk. The alternators used in the vehicles are to charge the batteries. Another thing you should note is to never charge the fully drained batteries with the alternator, and it is hazardous.

Both the generator and alternator have their own advantages and disadvantages.

The alternator has the stationary armature winding because -

  • Stationary winding can easily be insulated for high voltages and doesn't deal with any centrifugal forces
  • Hence Armature winding can be constructed more rigidly to avoid any mechanical stress
  • Elimination of brushes to collect the output current from the rotor.
  • The 3-phase output of armature winding can directly load without slip rings and brushes.
  • Since the DC current to supply field winding is lower, only two slip rings are required, which are of very light construction.
Note that any alternators rated above 5 kVA employ the stationary armature and revolving field winding (rotating magnetic field).

Alternators are capable of generating electricity at the specified frequency.

When prime mover speed is lower, the salient rotor is used in an alternator. So as the number of poles increases, the RPM will decrease.This same concept is used in water turbines where the prime mover speed is very low. But all commercial generators or portable generators use a cylindrical design with a two-pole arrangement to cope with high rotation speeds.

Output Current

Alternators can only supply the AC electricity while the generators can provide the AC as well as DC currents.


Another major difference between them is the constructional one. For an alternator, the magnetic field rotates with the rotor as the field winding will be placed on the rotor. While for the generator the field stays stationary and the armature rotates on the rotor, the field winding will be situated on the stator.


The alternators used in power stations are usually large and they accommodate large areas. On the other hand, the portable generators rated below 10Kw are not that large and won’t require that much space.

The power output

In alternators you can change the voltage output by adjusting field current which is achieved through an automatic voltage regulator. The latest inverter generator can regulate their speed to produce less power without sacrificing the desired frequency.


For an alternator, there is no need for a polarization. But, the generator will need to be polarized after it is installed.

Use of them

Alternators and generators, due to their differences, used for different purposes. Alternators are used in power stations and the generators are used where electricity needs are small.


That’s it. Most of the important things related to alternator and generator we have covered in this article. They look the same and have the same function to generate electricity. But they differ from each other in many things.

Their construction is different, one of them can supply the DC power and one of them can’t. These differences led them to be useful and suitable for different applications. You can’t use one instead of another.


7 Motor Parts and Their Common Faults

Understanding common motor problems is an important aspect when it comes to understanding engineered products or machinery. This comes in handy in many unfavorable situations, so one can define the appropriate solution and protective measure for such faults and mishaps. This also makes it important to understand various important terms related to assessing the parts and the working structure of your motors even during onsite testing of motors.

cut away view of an electric motor
Cut Away View of an Electric Motor (Credit: Wikimedia commons)

Here we have noted down

Some common motor problems caused by certain parts


This mechanical component in your motor is basically used to transmit torque and rotation. Shaft misalignment is the most common problem when it comes to this particular part. This will destroy your bearings before their complete working life. Analyze your motors through a vibration measurement procedure and check the force and the load that your motor is put through when they are running to avoid wear and tear.


Rotor elements can likewise help decide the reason for untimely gear disappointment. A fan's exhibition can be influenced by typical wear. On the off chance that appropriate protection support isn't executed, rotors may turn out to be slim and ultimately break.


On the off chance that you sense that your motor comes up short on the force it once had, or it's increasingly hard to begin, test your source coils. It is doubtlessly going to bite the dust. While you test it, you may need to likewise test your pick-up coil, as it could be failing as well. The actual stator may be dead and isn't sending any current to the battery. Never forget to replace your stators connectors. A bad connection generates heat, and heat fries the connector, making a short circuit that may burn your stator and other electrical parts.

Bearing Issues

In the three-phase machine, two sets of bearings are installed within the engine lodging, for supporting the machine shaft. They comprise an external and inward ring which is called races and a bunch of moving components which are called bearings. The bearing balls, both external and internal ring are damaged because of which the motor completely jams or gets struck. Bearing issues can also be checked by vibration measurement.

Insulation Brakdown

The most regular disappointment in electrical hardware is the degradation and breakdown (flashover) of the insulation. Natural protection material comprises enamels, resins, varnishes, or polymers that are applied to the steel surface to give high inter-laminar (between windings) resistance as found on most air-cooled apparatus and some oil-submerged transformers.

Hipot test

Another form of Electric Motor Testing is A hipot (high potential) test, additionally called a dielectric strength test, which checks for shortcomings in the link or wire protection. To play out this test, you apply flow between the electrical circuits and the edge. Note that particular overvoltage levels applied are subject to the motor and its predetermined voltage.

During this type of electric motor testing, you measure the overflow of current and figure the comparing mega-ohms even during onsite testing of motors. Zones with lower or higher than recommended mega-ohm readings have damaged protection.

Motor winding resistance

The objective of an machine winding test is a disconnected test used to find winding issues. You ought to play out this test at whatever point you see breaks or burns, or if you've noticed a burning smell coming from the machine. You will begin by clearing off the windings with shop air and investigating them. Then, set the multi-meter to midrange and design it to gauge resistance in ohms, at that point contact the leads together to confirm that the reading is 0 ohms.


Power System Stability

Power System Stability is the ability of a power system network to regain its equilibrium state even after being subjected to a disturbance. The main objective one must understand in power transmission is that the maximum amount of real power is aimed to be transferred to the load. Achieving this is practically not possible due to frequent load variation (either increase or decrease), but with various methods and analysis operating the system in the most stable region can be implemented and that is where this area of study comes into the picture.

Understanding the type of instability introduced into the system, the network is brought back to its equilibrium operating condition to achieve maximum power transfer. Let us first understand the main parameters that need to be taken into account to ensure a stable network.

We know the equation to determine the real power transferred in a transmission line:

Pe =  
EV sin𝛿


Pe = Magnitude of real power transferred
E = Excitation voltage
V = Terminal Voltage
𝛿 = Load angle/ Power angle (the angle between the Excitation voltage phasor and the terminal voltage phasor)
X = The total reactance

Therefore the relation can be plotted as follows:

Power Angle Curve

This is defined as the power angle curve.

If we notice, as the load angle increases the power transferred also increases and reaches the maximum at 90°. But, when it further increases the power transferred decreases significantly.

Thus, the load angle should be maintained in such a way that the power should not be decreased.

A change in load results in a number of issues:
  1. Change in frequency
  2. Change in load angle
  3. Change in rotational characteristics (especially speed of the machine)

Thus, a variation in load makes the system lose its synchronism and that is brought back with the help of Load Frequency Control.

The system stability can be classified depending on the type of disturbances it incurs in the system. They may be classified into:

  1. Steady State Stability
  2. Transient Stability
  3. Dynamic Stability

Steady State Stability

The ability of the machine (synchronous machine) to deliver maximum real power to the loads by maintaining equilibrium even when it experiences a small and gradual variation of load. Small load variations may occur when the frequency of oscillations made by the rotor is less than the natural frequency of the system (basically the change in rotational characteristics of the synchronous machines may fall under this category).

Transient Stability

Transient Stability is the ability of the machine to deliver maximum real power to loads when it experiences a sudden and large variation of load. This type of variation of the load is due to the occurrence of three-phase fault that lasts for a few cycles. The types of three-phase faults may be:


Dynamic Stability

The ability of the system to remain stable against smaller disturbances that do not last more than a few seconds. These smaller disturbances may occur due to random small variations in load or power generation levels. If these disturbances are cleared in few seconds, the system is said to be dyanamically stable.


There are a few assumptions taken and need to be kept in mind while analyzing the stability of a power system network.

  1. Effect of the shunt capacitance is neglected
  2. The resistance is neglected
  3. Mechanical input to the alternator is assumed to be constant (angular velocity is constant, running at synchronous speed)
  4. Effect of damper winding is neglected

Author: Vaishnav Chathayil is pursuing his B.Tech. in Electrical and Electronics engineering at National Institute of Technology, Calicut.

Power System Security


The sole objective of any power system network is to transmit power within its acceptable limit. The network should also work or stay under its limits event under any contingency. Contingencies may be of any type:

  1. Generator outage
  2. Line outage

Thus, irrespective of the issue evolved in a network, the power transfer between generating units and its loads must be “secure”.
The following article deals with what power system security means and how a power system network is classified into various states of operation.

What does Power System Security mean?

Power System Security may be defined as: The ability of a power system network to withstand contingencies(changes) and remain in its secure state or operate within its acceptable limits.

Various parameters may be taken into consideration and each have their own constraints. Violation of any such constraints may deviate the network’s secure operation. The constraints to be met for a secure operation are:

Inequality Constraints:
Pgimin ≤ Pgi ≤ Pgimax
Vimin ≤ Vi ≤ Vimax
Qgimin ≤ Qgi ≤ Qgimax
fmin ≤ f ≤ fmax
Pgi - real power generated from ith unit
Vi - voltage magnitude
Qgi - reactive power generated from ith unit
f - frequency

Equality Constraints:

Total Generated Power from all the units = Power demand + Power loss

If these constraints are met irrespective of any disturbance or change in the system, then the network is in secure operation.

Functions of Power System Security

The two functions that are taken care of under power system security are:
  1. Security Control: Make sure all the parameters are within their limits.
  2. Security Assessment: Detects the change in the parameters and identifies in which state the system is operating in.

System State Classification

Dyliacco’s classification:

In 1968, Dyliacco was the first one to introduce the classification of states in power system security. The operating states were classified into:
  1. Preventive State: this state basically highlights the secure operation of the system. It states that the system is working under its parameter limits and is also capable of withstanding the contingencies that occurs. Thus the operator on analyzing the situation should take preventive measures in advance and let the system not deviate from its state even during the contingency.
  2. Emergency State: This state indicates that the system constraints has been violated, I.e., it is not operating in its limits.
  3. Restorative State: In this state power transfer does not take in some parts due to outage I.e., contingency occurs in some parts of the system. Thus necessary action is to be taken to deviate it back to the normal state.

Dyliacco’s classification Power System Security

L.H. Fink and K Carlsen’s classification:

In 1978, the next type of state classification was suggested by Fink and Carlsen. In their classification the operating states are of 5 types:
  1. Preventive
  2. Alert
  3. Emergency
  4. Extreme
  5. Restorative

The following state transition diagram can be used to explain the flow that take place.

Normal00The system is secure and all constraints are met
Alert0 0 When the constraints are on the verge of violation,I.e., the operator is notified to foresee contingency
Emergency0 1 When inequality limits are violated
Extreme1 1 When both equality and inequality limits are violated
Restorative1 0 The inequality limit violation has been sorted but the load demand is yet to be satisfied.

*EC= 0 (equality constraint is met)
IC=0 (when inequality constraint is met)
Each becomes 1 when both are not met

In the extreme state it is the situation where blackouts occur and restoring it back to normal state may take hours or even days. Thus maximum the operator tries to deviate it from that state.

L.H. Fink and K Carlsen’s classification Power System Security


A governor in general refers to:

A device that is used to sense the quantity (that is proportional to speed) and regulates the speed of a machine.

There are many types of governors used in many applications. One of which we will be focusing in this article is the Fly ball Governor.

Turbine Governing System:

Turbine Governing System
Turbing Governing System (Credit: Vaishnav Chathayil)

Where, H.P. Oil refers to High Pressure Oil
NOTE: Point E is always fixed.
The turbine governing system consists of the following parts:
  1. SPEED CHANGER: This part of the system is used to provide a constant power setting to the turbine in order to get a constant output under steady state condition.
    It has a lever that can be lowered or raised. Changing the position of the lever changes the position of the Steam Inlet valve.
    NOTE: Changing the position of the lever does not alter the position of the fly balls.
  2. GOVERNOR MECHANISM: In this governing system a Fly ball Governor is used. It is also called a centrifugal Governor. This part of the system senses the change in frequency.
  3. HYDRAULIC AMPLIFIER: It has two main sub parts:
    • Pilot Valve
    • Piston Arrangement
    The amplifier also has an inlet through which High Pressure Oil is let in.
  4. LINKAGE MECHANISM: This is the most important part of the system as, based its movement the piston changes and also it controls the position of the Steam Inlet Valve.

Working of Turbine Governing System

The working of this system can be considered in two cases:
  • CASE 1: When the point B is fixed
  • CASE 2: When the point A is fixed
Let us see in detail what happens in each case.


Depending on the demand (load) the lever at the speed changer is varied. Let us see the case when the load high as a result more steam need to be let in to increase the mechanical input to the generator. The lever lowered and point A moves downward. Notice that B is fixed, the downward movement of A leads to an upward movement of C and D as well. Point D is in turn connected to the pilot valves. Now, when D moves upwards, the upper pilot valve opens and let the High pressure in to push piston in the Hydraulic Amplifier downward.

The piston is connected to the Steam Valve on the upper end, and it opens thus letting in the steam. Hence, the needed mechanical input is provided to meet the demand.


Now the power system is under steady state condition. But, it is seen that the load decreases. This results in a change in frequency in the system. We know that when there is an increases in load the frequency increases and this change is sensed by the governor in the governing system.

The fly ball governor works in such a way that:
  1. If there is an increase in frequency (indicates increase in shaft speed) the fly balls move outward.
  2. A decrease in frequency (indicates decrease in shaft speed) the fly balls move inward.

Consider a case when the load is reduced then it results in increase in frequency which results in the outward movement of the fly balls. On moving outwards the point B is pushed downwards that further results in pulling the points C and D downward. Now, when D moves downwards, the lower pilot valve opens and lets the High pressure in to push piston in the Hydraulic Amplifier upward thus closing the Steam Valve and reducing steam input.

Hence, reducing the surplus mechanical input provided.


Change in load Speed Fly ball Point B Point C & D Inside Hydraulic Amplifier Input Steam Valve
Increases Decreases Move outward Downwards Downwards Upper valve moves upwards Open
Decreases Increases Move inward Upwards Upwards Lower valve moves upwards Close
Thus, this is how the steam input to the turbine is controlled during the variation of loads.


Loads are variable parameters and they never remain constant. Based on the demands their intake varies. As a result, the power generated by the alternator needs to meet these demands.

Load Frequency control is a method that helps in maintaining the frequency of the network at its rated value i.e., 50Hz in India. This article deals with the process that goes about when the load varies in various cases.

Let us take an example,
Consider the initial state to be as follows,

Load connected to the bus = 200MW
Power generated = 200MW

Now it is observed that the,
Which means it leads to the stable operation of the system.

Now the frequency will also be at its rated value. Moreover, the machine (Synchronous Generator) will run at its synchronous speed.

But, as we mentioned earlier the load of the system is never a constant. Thus there are two possibilities,


Now let us see the detailed effects of each case.


Consider the demand increases and the load connected to the bus changes to 300MW. Now the values are,

Load connected to the bus = 300MW
Power generated = 200MW
Now it is observed that the
As a result the following occurs:
  1. When it is observed that 100MW is required from the load side, the energy that is needed is supplied by the stored kinetic energy of the machine. The K.E. is produced by the rotating parts of the machine:
    Kinetic energy of  synchronous generator
    K.E-Kinetic Energy (J/joules)
    I-Moment of Inertia (is a constant)
    ω - Angular velocity (rad/sec)
    Thus, 100MW is supplied by the stored K.E and its value decreases.
  2. As observed in the equation 1, the,
    K.E.∝ ω2
    Thus, when K.E. decreases, the speed of the machine also decreases.
  3. The speed of the machine and its frequency are related by the relation,
    speed of synchronous machine

    Thus, when the speed decreases, it, in turn, reduces the frequency and if the new frequency is fnew, then,
    fnew < 50 Hz
    Which not acceptable for a stable operation.


Consider the demand decreases and the load connected to the bus changes to 150MW. Now the values are,

Load connected to the bus = 150MW
Power generated = 200MW
Now it is observed that the,

As a result the following occurs:
  1. When it is observed that 50MW is produced in surplus the generator side, the energy that is needed is absorbed is added to the stored kinetic energy of the machine.
    The reason is, there needs to be a balance in energy (due to the Law of Conservation of energy).
    Thus, 50MW is added to the stored K.E and its value increases.
  2. As observed from the equation 1, when K.E. increases, the speed of the machine also increases.
  3. From equation 2, when the speed increases, it in turn increases the frequency and if the new frequency is fnew, then,
    fnew > 50 Hz
    Which is also not acceptable for stable operation.
Now, we have observed that,

Change in load ⇒ Change in Power Generated ⇒ Change in rotor speed ⇒ Change in Frequency

The change in frequency can be sensed using a device called a Governor. The Governor detects the change in frequency and then insists to change the Steam valve position.

This is done because by adjusting the valve position based on the change in frequency, we can change the steam input to the turbine. As the turbine is mechanically coupled to the Synchronous Generator, by adjusting the speed of the turbine it in turn adjust the mechanical input to the rotor.


Change in load Change in frequency Steam valve position Steam input Mechanical input to generator Power generated by the generator
Increases Decreased Open more Increased Increased Increased
Decreases Increased Close more Decreased Decreased Decreased

Now adjusting the mechanical input to the rotor, it also adjusts the Power Generated and this is how the change in load is met and the frequency is adjusted back to its rated value.

[Also Read: Synchronization of Alternator]
