Electric Motors Lubrication guide; Lubrication of electric motors

 Electric Motor Bearing Lubrication

Proper lubrication of moving part is very essential so as  lubrication of electric motor bearings is essential to maintaining them in peak operating condition which will leads to reducing unnecessary motor downtime.

Grease Lubrication

Motor bearings greasing is done because grease has properties as a lubricant of its simplicity of application and unique characteristics.

The primary functions of an electric motor bearing grease are to:

• Reduce friction and prevent wear

• Protect bearings against corrosion

• Act as a seal to prevent entry of contaminants

Grease is a semi-solid lubricant composed of following ingredients

(i)             Base oil

(ii)            Thickener and

(iii)           Additives.

 These components are combined in complex chemical reactions under controlled temperatures and pressures.

 The base oil used in greases may be

(i)             Mineral

(ii)            Synthetic.

Mineral oils are adequate for most electric motor bearing applications. However, synthetic base oils may be required for extreme temperature applications or where longer re-greasing intervals are desired.

Main function of  the thickener is that it serves as a carrier for the oil and prevents it from leaking out of the application. Some common thickeners include metallic soaps that can be composed of calcium, lithium, sodium, aluminum or barium and complex metallic soaps such as lithium-complex. A thickener increasingly employed in electric motor bearing lubrication is polyurea, Unirex N3.

Polyrex EM greases utilizes a polyurea thickener.

As with many lubricating oils, additives are frequently used to impart special properties to the grease.

Commonly used additives include, corrosion inhibitors, anti-wear or extreme pressure agents, oxidation and corrosion inhibitors, pour point depressants, lubricity agents, and dyes or pigments.

Choosing the Right Electric Motor Grease

The following criteria may be used as typical indicators of a good electric motor grease:

(i)              Viscosity:

 The typical mineral oil viscosity in an electric motor grease is in the range of 500 to 600 SUS at 100°F .Oil viscosity should be appropriate for the load and speed of the application at operating temperature. This will help to insure maximum protection and component life. Your electric motor builder may provide a specific recommendation.

(ii)             Consistency:

A grease’s consistency or firmness is stated in terms of its NLGI (National Lubricating Grease Institute) grade, which ranges from 000 to 6. The consistency of a grease should be appropriate to the application, as it affects pumpability and ability to reach the areas to be lubricated. A NLGI 2 grade grease is the most commonly used in electric motor applications.

(iii)            Oxidation Resistance:

 Electric motor greases should have outstanding resistance to oxidation. This extends the life of bearings running at high speeds and high temperatures. ASTM D 3336 High Temperature Grease Life test results give a good indication when operating under extreme conditions. Choose a grease with a high ASTM D 3336 oxidation life.

(iv)               Anti-Wear:

Unless a motor is mounted so there is a thrust load on the bearings, it is generally advisable to use a grease without extreme pressure (EP) additives. EP additives can shorten the life of the grease and should not be recommended where they are not needed. On the other hand, bearings designed to handle heavy thrust loads may require a grease with an EP additive.

(v)            Dropping Point:

The dropping point gives an indication of the temperature at which the grease will melt or the oil will separate from the thickener. Due to the high temperatures that can be reached in an electric motor bearing, a grease with a high dropping point is frequently desirable. Lithium complex greases and polyurea-thickened greases both have dropping points of approximately 500°F or higher.

(vi)            Shear Stability:

 ASTM D 217 Cone Penetration of Lubricating Grease test measures the consistency of the grease after it has been worked 100,000 strokes. An electric motor bearing grease should soften no more than 1 to 1.5 NLGI grades in this test. An electric motor bearing grease that softens more than that may leak out of the bearing with age.

Adding Grease to Electric Motor Bearings

Greasing of the motor bearings is done through points provided at motor bearing ends. It is important to know when to do greasing of motor and what quantity will be required for greasing of motor as lower amount of grease and extra amount of grease will leads failure of motors.

Re-greasing Intervals

Electric motors utilizing double shielded or double sealed bearings also known as double Z bearings, which are typically of the lubricated-for-life design, usually do not require re-greasing.

On the other hand, all others, those being open or single shielded or sealed bearings, should be re-lubricated periodically to replace grease that has deteriorated, leaked away, or become contaminated. Generally, operating conditions will dictate the re-lubrication interval required.

All greases deteriorate at some rate, even under moderate operating conditions. The principal causes are oxidation, excessive oil bleeding, and mechanical working. At high temperatures, oil evaporation may also be a factor. Oxidation eventually increases the oil viscosity and hardens the soap. Some oil bleeding is desirable, but too much reduces the ability of the grease to maintain an effective lubrication film. Mechanical working, or shearing, may change grease properties such as consistency, making the grease less suited to the application. Excessive oil evaporation may harden the grease. Deterioration often ends in hard, dry, deposits that can neither lubricate bearings nor protect them against contaminants.

Operating and other factors that influence relubrication frequency include: temperature, continuity of service, quantity of grease in housing, size and speed of bearing, vibration, exposure to contaminants, effectiveness of seals, and the grease’s suitability for the particular service.

1. High grease temperatures increase the oxidation rate, doubling it for every 18°F (10°C) rise above 120°F (49°C). High temperature also tends to increase the rate of bleeding and evaporation of the oil. Additionally, grease tends to soften as temperatures increase and may become fluid enough to leak out of housings. Other things being equal, operating at high temperatures will require more frequent relubrication, or the use of a high temperature grease.

2. Continuity of service means hours of service per day or other time unit. A grease continuously subjected to deteriorating factors will need replacement more often than the grease in a bearing used only occasionally.

3. A large quantity of grease in a properly designed housing will last longer than a small quantity in a proportionally smaller housing. The small quantity will be reworked more often than an equal portion of the large quantity and will not benefit from reserve capacity (including more oil and additives). Under moderate conditions, however, a small quantity of grease in a factory lubricated sealed or shielded bearing may last a long time, perhaps several years.

4. The Dn value of a bearing (bore diameter in mm x speed in rpm) is proportional to the linear speed of the rolling

elements and may be used as a guide to determine relubrication frequency. In bearings operating in the Dn range of 150,000 to 200,000 or more, grease in the path of the elements is severely worked and heated. Such bearings require more frequent relubrication even with correctly selected grease that does not slump excessively. Some bearing manufacturers use Ndm (speed in rpm x pitch diameter of the bearing) instead of Dn. This method produces somewhat higher reference values, but considers the effect of rolling element size and the bearing’s cross section dimensions.

5. Vibration causes grease to feed more freely into the rolling elements’ path, where it is worked and heated excessively. This reduces grease life, especially in high speed bearings. Churning and shearing in bearings “mills down” some greases, which become fluid enough to leak excessively. Either factor means more frequent relubrication.

6. More frequent relubrication usually will be required if the grease is marginal in any major characteristic — oxidation, bleeding, pumpability, antiwear and antirust properties, or mechanical stability.

It is not a simple matter to decide when and how often to relubricate. Generally, the decision reflects experience and the machine builder’s and grease supplier’s recommendations.

Relubrication intervals for most rolling element bearings range from two weeks to two years although for many it is once a year during scheduled maintenance shutdowns. At the lower extreme, bearings running at or near their speed limits may require relubrication as often as every six to eight hours.

It is important to regrease on an appropriate schedule so that the old grease remains soft enough for purging. Bearing or equipment manufacturers recommend relubrication intervals based on operating conditions and type of grease. Typically, light to medium duty electric motors, that run continuously, will require at least annual relubrication. Reduce the relubrication interval by half for every 10°C above the nominally recommended temperatures.

Two commonly used methods for determining the correct  relubrication frequency follow.

1. The first utilizes the following equation:

Frequency (hours) = {[14,000,000/(shaft rpm)(Bearing ID)^1/2

mm] — [(4)(Bearing ID) mm]}{F bearing type}{F temperature} {F contamination}

 where,

F bearing type = 1.0 for spherical or thrust bearing, 5.0 for cylindrical bearing, 10.0 for ball bearing

F temperature = 1.0 for under 160°F, divide by two for everyc20°F above 160°F

F contamination = 0.1 to 1.0 depending on the level of contamination—motor bearings normally 1.0

2. The second method utilizes the following graph for determining relubrication frequencies:

Determining the Correct Amount of Grease

Determining the correct amount of grease for an electric motor bearing is one of the most important steps in initial greasing and in regreasing of the bearings. An insufficient amount of grease could lead to bearing failure due to lack of lubrication. On the other hand, over-lubrication can also lead to bearing failure and cause problems due to migration of the lubricant in to the windings. One of the two methods following is frequently used for determining the quantity of grease to be added to a bearing:

1. 1/2 to 2/3 of the free space in the bearing — when operating speed is less than 50% of the limiting speed of the bearing.

1/3 to 1/2 of the free space — when the speed is more than 50% of the limiting speed of the bearing.

2. Another method of determining the appropriate quantity of grease to fill the bearing is determined by the following equation. This is a simple method of calculating the amount of grease needed for a standard application.

Quantity of grease (g) = Outer bearing diameter (mm) X bearing width (mm) X 0.005, or

Quantity (oz) = 0.114 X (bearing OD) in X (bearing width) in

It is common practice to pack the bearings as well as the bearing housing with grease. In addition to holding the bearing in place, the bearing housing also acts as a grease reservoir. The following may be used as a guide to filling the housing with grease.\

• 30% to 50% fill

Typically used. For very high speeds the lower limit should be used in order to reduce churning and overheating of the grease. Overpacked bearings tend to overheat, and to overheat even more at higher speeds.

• 50% to 75% fill

For slow speeds, or in the absence of other methods of regreasing, fill the housing 50% to 75% with grease. After the housings are packed and the motor started, the rolling elements will push the excess grease from between the races into the housing, leaving only the thin lubricant film needed to minimize friction and wear.

• Full pack

 A particularly dirty environment may call for the housing to be completely filled, but the bearing itself will only contain enough grease for lubrication. The pressure relief method will also produce a full pack.

One full pack method begins with the bearing filled with grease and the housing 75% full, leaving just enough space to receive the excess grease pushed out by the rolling elements. If the housing were actually packed full, the grease between the rolling elements could not escape and would be severely worked.

Inverter working principle; How Inverter works; AC Inverters

Inverters are now integral part of every household. As they serve the better and cheap source of supply in case of power cuts. Earlier days Diesel generators were most widely used for household in case of power cuts.

There is always curiosity that how an inverter works.

Working Principle:-

In inverter Alternating supply is first converted into DC supply then again into alternating supply that is why it’s name is inverter.

There is obvious question in mind that why there is need for conversion into DC??

Answer for the same is that for inverter working Battery is required which is needed to be charged through DC when power source is available and when power supply wasn't available that DC power supply which is stored by Battery is reconverted into AC supply through it’s inverter action.

Also when power supply is available then there is no need for Inverter action in that case all points which were on inverter will be charged through power supply. Means that inverter will get bypassed for doing that phase which is coming from power supply source is directly connected to inverter o/p socket.

Wiring of points through Inverter:-

To get inverter supply at points one single wire is taken from inverter O/p and will connected at points phase points which are to be connected through inverter. Neutral is taken from the source.

Now confusion arises why there is no neutral required from inverter O/P?

Answer for the same is that Neutral from Power supply source is never disconnected even if there wasn't any power. That is why neutral is not required.

This doesn't mean that you can’t take neutral from inverter O/p. You can take the same but that will leads to extra cost of neutral wiring also.

Inverter Connections:-

An inverter consists of following components:-

1.      Inverter

2.      Battery

Below diagram will shows you how to do wiring of an Inverter:-

Due attention of positive and negative terminals must be taken before connection of battery to inverter. As wrong connections may leads to short circuit.

Inverters of various sizes available in the market from 300 VA to KW’s depending upon requirements and backup required. More batteries required if more backup required. 

Earth Pit Resistance measurement method; Fall of Potential method

Earthing is used to protect both human and equipment's from abnormal currents.

These abnormal currents will get dissipated safely when properly conducted to earth via the electrode.

There are three components to the resistance:-

1.     Resistance of the electrode materials

2.     Contact resistance between the electrode and the soil surrounding it

3.     Resistance of the surrounding earth.

The contact resistance between earth and the electrode is minimal if the electrode materials Cleaned properly and unpainted.  Even if steel get rusted even then rusted steel ground rods have little contact resistance because the iron oxide readily soaks up water and has less resistance than most soils. It has been found that the resistance of the surrounding earth will be the largest of the three components as described above.

A proper earthing system generally works on the system that an earth electrode system buried in the earth radiates current in all directions which will get dissipated at some distance away depending on the soil’s resistance to current flow which is also known as soil resistivity.

Earthing system consists of multiple electrodes buried at distance and are connected in parallel and a grid is formed so as to minimize grid resistance and whenever fault occurs that fault current will flow through grid and ultimately get dissipated.

 

Generally an earth electrode can be thought of as being surrounding by shells of earth, each of the same thickness as shown below. The shell closest to the electrode has the smallest surface area and offers the greatest resistance as resistance is inversely proportional to area. The next shell has larger area then nearest shell so it has lower resistance, and so on. A distance eventually will be reached where the additional earth shells do not add significantly to the resistance.

Earth electrode resistance is measured to remote earth, which is the earth outside the electrode’s influence. A larger electrode system requires greater distance before its influence decreases to a negligible level.

Measuring Earth pit Resistance

Earth pit resistance is measured by using earth pit tester. Which are shown below:-

There is following process by which earth pit resistance can be measured. There are four terminals in earth pit tester described as ;

C1 & C2 known as current terminals, P1 & P2 known as potential terminals.

One current terminal (C1) is connected to the earth electrode under test and the other (C2) to a probe driven in the earth some distance away. The test set injects a current into the earth between the two current terminals. One potential terminal (P1) also is connected to the earth electrode but the other potential terminal (P2) is connected to a separate probe driven in the earth between the electrode and the current probe (C2). The potential probes detect the voltage due to the current injected in the earth by the current terminals. The test set measures both the current and the voltage and internally calculates and then displays the resistance

Resistance= Voltage/ Current

When measuring the resistance of earth electrode systems generally fall of potential method is used.

Fall of Potential Method:-

This method is most widely used to measure earth pit resistance. Procedure for the same is discussed below:-

The basic procedure for the Fall-of-Potential method is to first connect the test set terminals C1 and P1 to the earth electrode under test, connect the test set C2 terminal to a current probe located some distance from the earth electrode and finally connect the test set P2 terminal to a potential probe located a variable distance between. The two probes normally are located in a straight line. At each potential probe location, the resistance is recorded (a form is provided in

1. Connect C1 and P1 terminals on the test set to the earth electrode as shown in fig below

2. Drive a probe into the earth 100 to 200 feet from the center of the electrode and connect to terminal C2. This probe should be driven to a depth of 6 – 12 inches.

3. Drive another probe into the earth midway between the electrodes and probe C2 and connect to terminal P2. This probe should be driven to a depth 6 – 12 inches.

4. Record the resistance measurement.

5. Move the potential probe 10 feet farther away from the electrode and make a second measurement.

6. Move the potential probe 10 feet closer to the electrode and make a third measurement.

7. If the three measurements agree with each other within a few percent of their average, then the average of the three measurements may be used as the electrode resistance.

8. If the three measurements disagree by more than a few percent from their average, then additional measurement procedures are required.

Digital Multimeter working principle; DMM working

Digital multimeters are most widely used in every industry as it used for measurement of Voltage, Current, Resistance, Capacitance and various other parameters. DMMs have been available for very several years. Yet it is still challenging to locate advice about how a digital multimeter works.

The operation of a digital multimeter is comparatively uncomplicated, although there are obviously differences in how digital mulimeters work if they're from different makers.Despite this, there are several similarities and some general principles of how digital multimeters work.

Fundamentals of how a DMM functions

The key process occurring within a digital multimeter for any measurement is that of voltage measurement. All other measurements are derived from this basic measurement.

So the best technique for understanding how a digital multimeter functions is in understanding this procedure.

There are many kinds to digital converter, ADC. Nonetheless the one that is most widely used DMMs in digital multimeters, is currently referred to as SAR or the successive approximation register. Those used in test equipment normally have 16 bits or perhaps more dependent upon the program, although some SAR ADCs may just have resolution amounts of 12 bits. Commonly with speeds per second resolution levels of 16 bits are generally used, for DMMs. These levels of speed are more than adequate for most DMM applications, where high degrees of speed aren't generally needed.

Consecutive approximation register ADC used in most DMMs

Most DMMs were used in by serial approximation register ADC

As the name implies, the successive approximation register ADC functions by successively homing in on the financial value of the voltage that is incoming.

The first stage of the procedure is for the sample and hold circuit to sample the voltage at the input of the DMM and to hold it steady.

With a steady input voltage the register begins at half its total scale value. This would typically need the most significant bit, MSB set to "1" and all the remaining ones set to "0". Assuming the input voltage could be anywhere in the range, the mid-range indicates that the ADC is set in the middle and this provides a more rapid settling time. As it only needs to transfer a maximum instead of possibly 100%.

The input voltage's output will begin at 1000. The comparator output will be low and that'll drive the register to a amount of 0100 if the voltage is less than half the maximum ability. If the voltage is above this, the register will go until it homes in on the nearest value.

It may be seen that SAR converters, need one approximating cycle for each output bit, i.e. an n-bit ADC will require n cycles.

DMM operation

To be able to completely understand how a digital multimeter operates although the analogue forms the essential component within the instrument, it is vital to look at a few of the other functions around the ADC.

Although the ADC will take very many samples the overall digital multimeter will not display or return every sample chosen. The samples are buffered and averaged to reach high precision and resolution. This will overcome the effects of modest variations for example sound, etc., sound created by the analogue first periods of the DMM being an important variable that must be overcome to achieve the greatest precision.

How a digital multimeter works

Operation flow diagram of a DMM for operation is shown as below

Measurement time

One of the key areas of understanding how a digital multimeter works is related to the measurement time. In addition to the fundamental measurement there are several other functions that are required and these require time. Consequently the measurement time of an electronic multimeter, DMM, may not always seem uncomplicated.

The overall measurement time is composed from several phases where different actions happen:

Switch time:

The switch time is the time needed for the instrument to settle after the input signal has been switched. Including the time to settle after a measurement type has been changed, e.g. from voltage to resistance, etc. In addition, it contains time to settle after the range has been shifted. If auto-ranging is included the meter will need if there is a range change required to settle.

Settling time:

A time that is particular will be demanded for the value to be measured to settle, once it has been applied to the input. This will overcome any input signal capacitance levels when high impedance evaluations are made, or ordinarily for instrument and the circuit to settle.

For AC measurements, the frequency of functioning must be taken into account because the minimum signal measurement time relies on the minimal frequency required of the measurement.

Auto-zero time: 

When autorange is chosen, or range changes are made, it is vital to zero the meter to ensure correctness. Once the correct range is selected, the auto-zero is functionality for that range.

ADC calibration time:

In some DMMs there is a calibration occasionally performed. This must be accounted for, especially where measurements are required under automatic or computer management.

It's always useful to understand how a digital multimeter functions in order to be able to make the greatest use and the most precise measurements. However it should be remembered that different multimeters from different manufacturers may work in different ways. Hence it is always helpful to consult with the manufacturer's instructions to comprehend how a digital multimeter works that are particular.

Surge Arresters; Surge arrester works principle; Surge Suppersors

We have discussed about Lightning arrester now lets discuss about surge arrester.

Although they both have same principle of working. In this article we will discuss about brief details about arresters. First you must know about what arrester is ??

Answer to this question is that The arrester provides a low-impedance path to earth from transient voltage or a lightning strike and after that restores to an ordinary operating conditions.

For simplicity you may consider a surge arrester similar to your relief valve on hot water heater or a boiler. High pressure will be released by it until there is a standard operating state achieved. The safety valve is prepared for another operation, when the pressure is returned to standard.

Whenever there exist a high voltage (greater than the standard line voltage) on the line, the arrester drains off the extra voltage and promptly furnishes a route to ground and therefore limits. The arrester then prevent any additional flow of current as clear from the name surge arrester used to address high voltage spikes. Surge arresters are used for in electronic circuits to isolate the electronic circuit from power circuit.

The arrester has two functions;

1.       It must provide a point in the circuit at which an over-voltage pulse can pass to ground and

2.       Second, to prevent any follow-up current from flowing to ground.

There are three types of surge arresters.

They are:

1. Expulsion type

2. Valve type arrester

3. Gapless metal-oxide type

Different types of protective devices are:

1.       Earthing screen

2.       Overhead ground wires

3.       Lightning arresters

1.       The Earthing Screen:-

Substation & the power station can be shielded against direct lightning blows by supplying earthing screens. On incidence of direct stroke earthing screen supplies a low resistance path where lightning spikes are conducted to ground.

2.       Overhead Ground wire:

It's the best way of providing protection to transmission lines. It provides damping effect on any noise as the lines acts as a short circuited secondary traveling along it. You might have seen HT lines along with overhead ground wire.

Limitations of Overhead Ground wire

(i)      It needs added price.

(ii)     There exists a chance falling across the line conductors, thus causing a short circuit error and of its breakage.

(iii)    Ground wires and the earthing display neglect to provide protection.

SURGE PROTECTOR TYPES:-

Type 1 Surge Protectors

Type 1 surge protectors are made to be installed where there is a direct lightning strike hazard high, particularly when the building has outside lightning protection system (LPS or lightning rod).

In this scenario IEC 61643-11 standards need the Course I test to be used to surge protectors: the injection of 10/350 microsec nerve impulse current in order characterizes this evaluation to model the immediate lightning strike impact. So these Type 1 surge protectors must be particularly strong to run this high energy pulsation current.

Type 2 surge protectors

These are used at the beginning of installation. i.e. either in main switch board or close to sensitive terminals. These guards are examined following the Class II evaluation from IEC61643- 11 based on 8/20 microsec pulsation current injection.

Type 3 surge protectors

In the event of remote gear or really sensitive, secondary phase is needed: these low energy SPDs could be Type 3 or Type 2. Type 3 SPDs are analyzed with a mixture waveform (1,2/50 microsec - 8/20 microsec) .

Types of Surge Arresters according to Class

1. Substation Class

Substation class arresters are commonly used in substations or electrical power stations and other high voltage constructions and places.

These arresters shield against overvoltages and both lightning, than it was created to manage when the electrical device has current.

These arresters are made to shield gear above the 20 MVA range.

2. Intermediate Class

Like substation group arresters, intermediate type arresters shield against spikes from overvoltages and lightning, but were created to be applied in moderate voltage gear places, including transformers, electric utility stations, substations or other substation equipment.

These arresters are designed to be used on gear in the range 1-20 MVA.

3. Distribution Class

Distribution group arresters are mostly discovered both dry-type and liquid-filled.

These arresters are less or discovered on gear.

These arresters are occasionally discovered on open paths that have direct connections to machines that were rotating.

These used in range of 100 KVA

4.       Secondary Class

These arresters cause overages that are high voltage to earth, though they don't short all the over voltage from a spike. Secondary category arresters offer the least number of protection and generally don't protect anything with a microprocessor, or solid state technology.

Lightning Arrester Working Priciple; How Lightning Arrester works

Lightning arrester is nothing more than a spark air gap with one side connected to a line conductor and the other side connected to earth. When the line-to-ground voltage reached the spark-over level, the voltage surge would be discharged to earth.

The modern metal oxide arrester provides both excellent protective characteristics and temporary overvoltage capability. The metal oxide disks maintain a stable characteristic and sufficient non-linearity and do not require series gaps

Current level in a Lightning Stroke,
Current levels in lighting stokes is as below:-
1 percent'of strokes exceed 200 000 A
10 percent of Strokes Exceed 80 000 A
50 percent of Strokes Exceed 28 000 A
90 percent of Strokes Exceed 8 000 A
99 percent of Strokes Exceed 3 000 A

The current in the majority of earth flashes is from the negatively charged cells and the flash current is, thus, a negative Row from cloud to earth there will be lighting strokes from positive charged cell but they are very few ones.

Sometime lighting stokes took place in span of 50 ms to 100 ms.

Voltage rise due to lightning
There will be few 100 million of volts in every lighting stroke.  These strokes can  generate heat of upto 54000 degree fahrenheit.

 The lightning stroke begins by the detailed descent in the cloud of a leader stroke step dancing some tens of meters. When the last measure brings the point of the leader adequately close to ground, the ground to join the point of down leader is left by an upward streamer.
This upward streamer's initiation is determined by an essential field being surpass at the world emission point and is a function of the charge - any improvement of the field and coming leader due to the earth's geometry. The amount of the streamer that is upward will be greater for charges that are greater and thus high flashes that are current will begin from high constructions that the field improvement is not low.
SIDE EFFECTS
Electrical Effects
It may additionally create a high potential gradient dangerous to creatures and men. In exactly the same general way the inductance must be considered due to the steep leading edge of the lightning pulsation.
The resulting voltage drop is so, the mixture of the inductive and resistive voltage elements.
Side Flashing
The stage of strike the protective system may be increased to adjoining metal' into a high potential with regard. There exists thus, a danger of flashover in the protective system any other metal on or in the construction. If such flashover occurs, part is released through internal setups, including wiring and conduits, and thus this flashover represents a danger to the occupants and fabric of the construction.
Thermal effects
As far as lightning protection is affected by it, the effects are confined to the temperature rise of the conductor whereby the current passes. Although the current is high, its duration is brief, and the thermal effect on the protective system is usually negligible. (This discounts the fusing or welding effects on damaged conductors ") In general, the cross-sectional area of a lightning conductor is chosen primarily to meet the demands of mechanical strength, meaning it's big enough to keep the rise in temperature to 1degC in case of copper conductor. The substitution of steel results in a rise of less than 10 degree C.
Mechanical Effects
Where a high current is discharged along parallel conductors at close proximity, or along one conductor with sudden bends, considerable mechanical forces are generated. Secure mechanical fittings arc, thus, crucial. A different mechanical effect used by a lightning Bash is primarily due to the abrupt rise in air temperature along which the charge is propagated in the channel to 30000 K and the ensuing volatile expansion of the adjoining atmosphere. That is because, when that of an arc route replaces the conductivity of the metal, the energy increases about one hundredfold.

Likewise, with a secondary flash inside the building, the shock wave can lead to damage to the building material.

Voltage spikes can be created by lightning in several of these manners. It can hit at the overhead power line or a primary power line that's blocks from your residence. Lightning can hit at division circuitry wiring in your house's walls.
Lightning can hit an item near your residence for example the earth or a tree itself and cause a spike.
Normal on and off changing actions of big electric motors or pieces of gear can also cause voltage spikes.
They are able to happen with little if any warning.

What is Lightning arrester??
A Device Used on Power Systems above 1000V to Protect other Equipment from Lightning and Switching Surges.
•It Does not Absorb the Lightning
•It Does not Stop the Lightning
•It Does Divert the Lightning to Ground
•It Does Clamp (limit) the Voltage produced by the Lightning
•It Only protects equipment electrically in parallel with it.


Below figure shows how a lightning arrester works.

Yellow line shows lightning path when arrester is installed.

Arrester Internal Structure:-

Above diagram shows internal of Lightning arrester which consists of MOV'S i.e. Metal oxide varistors .

The MOV Disk is a Semiconductor that is sensitive to Voltage. At normal Voltages the MOV disk is an insulator and will not conduct current. But at higher voltages caused by lightning it becomes a conductor.

Methodology to Suppress Voltage Spike and Lighting:
When there is a voltage spike created, it needs to equalize itself and it needs to do it as fast as possible. These matters appear to have little patience. The spikes will do whatever is necessary neutralize or to equalize themselves, even though it means short circuiting all your electronic equipment.

The way of supplying maximum protection for gear is fairly straightforward.
That is not, generally, a task that is difficult.

Step one is not complex.

Create a fantastic grounding system for the home electrical system. A large proportion of houses don't have a great grounding system. Many houses have /or a metallic subterranean water pipe which are part and one grounding pole. Typically, that is not adequate. The reason is not fairly difficult to describe. I doubt the drain could manage all the water. Your grounding system would respond to some huge voltage spike in exactly the same manner. As the water leaps out from the sink, the electricity looks for areas to go and jumps in the grounding system. They're a simple target.

Voltage spikes are interested in being directed to the grounding system, and they would like to enter the earth when they do. It's possible for you to accomplish this by driving grounding rods that are numerous around your house into virgin land. These poles should be UL approved and joined by a constant heavy solid copper wire that is welded to each grounding pole. This solid copper cable terminates at the last grounding pole and starts on the grounding pub interior of your electric panel. Avoid using clamps. The connection can corrode or become creating incredible resistance. This will become a roadblock to the electricity attempting to enter the earth around your house.

The should be found in land which easily takes electricity. Clay lands that are damp have become desirable. Lands with gravel, or rugged, sandy typically have high resistance variables. Electricity has a rough time dissipating into the. Resistance readings should take the range.

The second part of home spike protection would be to install a lightning arrester interior of your electrical service panel. These apparatus can be tremendously successful in intercepting substantial voltage spikes which go in the electric power lines. The voltage spikes are captured by these devices and 'bleed' them away to the grounding cable which we only spoke of. If for some reason you don't have enough ground poles, the arrester cannot, or a big enough grounding wire do its occupation. It must have the ability to send the spike immediately to the earth beyond your home. One is made by nearly every maker . Have a skilled electrician install this capability for you, if you don't have it.

The ultimate part of the protection strategy would be to install 'point of use' spike suppression devices. Frequently you'll see these named 'transient voltage surge suppressors'. They may be capable of just quitting the left over voltage spike which got past the lightning arrester and the grounding system. Themselves must be applied in conjunction with the lightning arresters and the grounding system.

The' point' spike suppression devices can be found in various degrees of quality. Some are not much worse than others. What sets the apart are several matters. Most of the time, you look to find out how speedy the's time is. That is frequently called clamping speed. Ensure the apparatus has a 500 volt maximum suppression degree was rated by UL. Check to see if it's an indicator, either sound or visual, which allows you to understand if it's not working. The units that are better offer both, in the event you install the apparatus out of sight. Check to see whether it offers various modes regarding protection. There's a difference! Check to see if it tracks the standard sine waves of routine household current. Irregularities can be caused by spikes . Ultimately, assess the joule rating. Try to find a device that has a joule rating or higher. Electric supply houses frequently are the ideal spot to look for these apparatus that are high quality.

Some devices also can shield your telephone gear at once. That is essential for those people that have computer modems. Huge voltage spikes can run into phone lines at the same time. These spikes can enter your computer! Do not forget to shield this line. Additionally, be certain the phone ground wire is tied to the updated electric grounding system.

Car AC working principle; Car Air conditioner

Air conditioning as names 'states' the conditioning of air. Air conditioner not only cools down the air , but also reduces humidity, or the moisture content. All air conditioners work exactly the same manner whether they're installed in a a vehicle, or in a building. Freezer or the refrigerator is an air conditioner too. Air conditioning is an area inside it's own right, but we'll adhere to the principal points or an automobile's air conditioning and the main parts used and a number of hints to keep the air-con system running properly.

There's energy used in removing moisture and the heat from the air in the automobile, and petrol is consumed by this because of the additional engine load.

The main principles of air conditioning are Evaporation and Condensation, then Compression and Expansion. To physicists and the engineer they talk of thermodynamics - but it 'll be explained by us in our own manner here: 

Below is schematic diagram for explaining how actually air conditioner works; 

Evaporation: 

You might have noticed that if you rub a little surgical spirits on the back of the hand, then your hand will feel cold. It is evaporation.  As the spirit evaporates, it takes away heat in the surface of your skin.

Condensation:

Maybe you have noticed when somebody walks in in the cold into a take away wearing spectacles, their glasses steam up? It's condensation.

Heat of Compression: 

Perhaps you have noticed when you pump up a bike tyre with a hand pump, that the end of the pump gets hot? This is known as compression also you have noticed that in deodorants also liquid filled in bottle is compressed. 

Compaction:

At some stage all gases will finally become liquid. An example of that will be a deodorant can - it is liquid (because you'll be able to hear it when you shake it) but is a gas when it hits your underarm and comes out. The pressure is higher, so the propellant interior is not gaseous.

Cooling by Expansion: 

Going back to the deodorant, you'll notice also how cold it feels that is because the propellant has only grown in volume quickly.

Anyway, enough about surgical spirits and takeaways, armpits, but those are the fundamental ideas that are not difficult enough to clarify.

Flexible hoses and tough tubing connect all the real elements of the air conditioning in your auto. Evaporation and condensation, expansion and compaction are the physics of why it works.

The refrigerant then condense at a higher pressure, and can evaporate at a low temperature. In the bad old days, R-12 was the refrigerant used in practically all cars. It was broadly available, however it was discovered to be a subscriber to the hole in the ozone layer of the earth's as it was a chlorofluorocarbon (CFC).

Here is how all the various parts of a car's air conditioning works:

Compressor: 

The compressor is the ac system, powered by a drive belt linked to the crankshaft of the engine's work horse. The compressor pumps refrigerant vapour under high pressure to the condenser, when the aircon system is turned on.

Condenser: 

The condenser is a device used to change the high pressure refrigerant vapor to a liquid. It is mounted in front of the engine's radiator, and it looks much like a radiator. The vapour is condensed because of the high pressure that is driving it in, which generates a fantastic deal. The heat is in turn removed by air flowing through the condenser on the outside from the condenser.

Receiver: 

The refrigerant that is now liquid moves to the receiver-dryer. It is a small reservoir vessel and removes any moisture that may have leaked into the refrigerant. Havoc is caused by moisture in the system, with ice crystals causing mechanical damage and blockages.

Expansion Valve:

The refrigerant that is pressurised flows in the receiver- drier to the expansion valve. The valve removes pressure from the liquid refrigerant so that it might expand and become refrigerant vapour in the evaporator. Air Conditioning

Evaporator: 

The evaporator is another device that looks similar to an automobile radiator. It's tubes and fins and is normally mounted behind the fascia. The cold low-pressure refrigerant vaporizes and absorbs heat from the atmosphere in the passenger compartment, as it is passed into the evaporator. The blower fan pushes air over the evaporator's exterior , so chilly air is circulated inside the automobile. On the 'air-side' of the evaporator, the moisture in the air is reduced, and the 'condensate' is collected and drained away.

Compressor:

The compressor then draws in the low-pressure refrigerant vapor to begin another refrigeration cycle. The refrigeration cycle then runs constantly, and is regulated by the setting of the expansion valve.

The whole process is reasonably straightforward when described like this. All air conditioning systems work with the same principle, even if the precise parts used may vary slightly between car manufacturers.

Hopefully that clarifies a little as to how that small 'A/C' button works on your own automobile, if you want it clarified a little more in depth afterward if you roll up your sleeves we can demonstrate the parts in your car next time you bring it in for a check or service here at AirconCars.