Electrical Standards From IEC 60134 to IEC 60298

IEC 60134à Absolute maximum and design ratings of tube and semiconductor devices

IEC 60137à Bushings for alternating voltages above 1000V

IEC 60146à Semiconductor Converters

IEC 60169à Radio-frequency connectors

IEC 60183à Guide to the selection of high voltage cables

IEC 60204à Safety of machinery

IEC 60214à On-load tap changers

IEC 60228à Conductors of insulated cables

IEC 60233à Tests on Hollow Insulators for use in Electrical Equipment

IEC 60238à Edison screw lampholders

IEC 60245à Rubber-Insulated Cables

IEC 60255à Electrical Relays

IEC 60268à Sound system equipment

IEC 60269à Low voltage fuses

IEC 60270à High-Voltage Test Techniques - Partial Discharge Measurements

IEC 60287à Calculation of permissible current in cables at steady state rating

IEC 60092-350à Shipboard Power cables-General construction and Test Requirements

IEC 60296à Mineral Insulating oils for transformers & switchgear

IEC 60297à 19-inch rack

IEC 60298à high voltage switchgear in metallic enclosure

IEC Standards in Electrical Systems from IEC 60027 to IEC 60099

IEC 60027 à Letter symbols to be used in electrical technology...

IEC 60034 à Rotating electrical machinery

IEC 60038 àIEC Standard Voltages

IEC 60044 àInstrument transformers

IEC 60050à International Electrotechnical Vocabulary

IEC 60062 àMarking codes for resistors and capacitors

IEC 60063 àPreferred number series for resistors and capacitors

IEC 60065à Audio, video and similar electronic apparatus - Safety requirements

IEC 60068àEnvironmental Testing

IEC 60071à Insulation Co-ordination

IEC 60073à Basic Safety principles for man-machine interface, marking and identification

IEC 60076à Power Transformers

IEC 60079à Parts 1-14 Electrical Installations in Hazardous Areas

IEC 60085à Electrical insulation

IEC 60086à Primary batteries

IEC 60094à Magnetic tape sound recording and reproducing systems

IEC 60096à Radio-frequency cables

IEC 60098à Rumble measurement on Vinyl Disc Turntables

IEC 60099à Surge arresters

Induction Motors Duty Cycles

Type of Duty

The following shall be the duty types:

Sl -Continuous duty
The motor works at a constant load for enough time to reach temperature equilibrium.

S2 -Short time duty
The motor works at a constant load, but not long enough to reach temperature equilibrium. The rest periods are long enough for the motor to reach ambient temperature

S3 -Intermittent periodic duty
Sequential, identical run and rest cycles with constant load. Temperature equilibrium is never reached. Starting current has little effect on temperature rise

S4 -Intermittent periodic duty with starting
Sequential, identical start, run and rest cycles with constant load. Temperature equilibrium is not reached, but starting current affects temperature rise.

S5 -Intermittent periodic duty with starting and electric braking
Sequential, identical cycles of starting, running at constant load and running with no load. No rest periods.

S6 -Continuous duty with intermittent periodic loading
Sequential, identical cycles of running with constant load and running with no load. No rest periods.

S7- Continuous duty with starting and electric braking
Sequential identical cycles of starting, running at constant load and electric braking. No rest periods

S8 -Continuous duly with periodic speed changes
Sequential, identical duty cycles run at constant load and given speed, then run at other constant loads and speeds. No rest periods.

American Wire Gauge; AWG calculations

AMERICAN WIRE GAUGE

By definition, No. 36 AWG is 0.0050 inches in diameter, 
and No. 0000 is 0.4600 inches in diameter. 
The ratio of these diameters is 92, 
and there are 40 gauge sizes from No. 36 to No. 0000, or 39 steps.

Using this common ratio, wire gauge sizes vary according to the following formula: 

The diameter of a No. n AWG wire is the gauge can be calculated from the diameter using and the cross-section area is

. Sizes with multiple zeros are successively larger than No. 0 and can be denoted using "number of zeros/0", for example 4/0 for 0000. For an m/0 AWG wire, use n = −(m−1) = 1−m in the above formulas. For instance, for No. 0000 or 4/0, use n = −3.

The ASTM B 258-02 standard defines the ratio between successive sizes to be the 39th root of 92, or approximately 1.1229322. ASTM B 258-02 also dictates that wire diameters should be tabulated with no more than 4 significant figures, with a resolution of no more than 0.0001 inches (0.1 mils) for wires larger than No. 44 AWG, and 0.00001 inches (0.01 mils) for wires No. 45 AWG and smaller.

Table of AWG wire sizes

The table below shows various data including both the resistance of the various wire gauges and the allowable current (ampacity) based on plastic insulation. The diameter information in the table applies to solid wires. Stranded wires are calculated by calculating the equivalent cross sectional copper area. The table below assumes DC, or AC frequencies equal to or less than 60 Hz, and does not take skin effect into account. Turns of wire is on a best-case scenario when winding tightly packed coils with no insulation.

In the North American electrical industry, conductors larger than 4/0 AWG are generally identified by the area in thousands of circular mils (kcmil), where 1 kcmil = 0.5067 mm². A circular mil is the area of a wire one mil in diameter. One million circular mils is the area of a cylinder with 1000 mil = 1 inch diameter. An older abbreviation for one thousand circular mils is MCM.The "Approxismate stranded metric equivalents" column lists commonly available cables in the format "number of strands / diameter of individual strand (mm)" which is the common nomenclature describing cable construction within an overall cross-sectional area. Some common cables are midway between two AWG sizes. Cables sold in Europe are normally labeled according to the combined cross section of all strands in mm², which can be compared directly with the Area column.

Outside North America, wire sizes for electrical purposes are usually given as the cross sectional area in square millimeters.International standard  manufacturing sizes for conductors in electrical cables are defined in IEC 60228.

Note that the area in mm² may differ somewhat from the numbers given in the table, depending on number of strands etc.

AWG chart is as shown below:-

 Rules of Thumb

The sixth power of this ratio is very close to 2, which leads to the following rules of thumb:

• When the diameter of a wire is doubled, the AWG will decrease by 6. (e.g. No. 2 AWG is about twice the diameter of No. 8 AWG.)
• When the area of a wire is doubled, the AWG will decrease by 3. (e.g. Two No. 14 AWG wires have about the same cross-sectional area as a single No. 11 AWG wire.)

Additionally, a decrease of ten gauge numbers, for example from No. 10 to 1/0, multiplies the area and weight by approximately 10 and reduces the resistance by approximately 10.

Full Load Speed of Induction Motor

Slip  and Full-load speed of Motor

The speed at which rated full-load torque is delivered at rated power output is full-load speed. It is

generally given as "RPM" on the nameplate. This speed is sometimes called "slip" speed or actual rotor speed rather than synchronous speed. Synchronous speed is the speed at which the motor would run if it were fixed to the ac power line frequency; that is, if it turned at the same speed as the rotating magnetic field created by the combination of winding pattern and power line frequency. An induction motor's speed is always less than synchronous speed and it drops off as load increases. For example, for 1800 rpm synchronous speed, an induction motor might have a full-load speed of 1748 rpm, this drop in RPM is due to slip of an induction motor.

Slip speed is difference between synchronous speed and actual rotor speed.

In induction motors Slip is directly proportional to torque of motor, so greater will be the slip greater will be torque generated in motor. So greater will be the induced emf.

When motor is running at no-load then it requires small torque to overcome mechanical, iron and other losses, therefore slip is small. 

Now when the motor is put on load greater torque will be required so slip will increase and correspondingly motor speed get reduced. So slip adjustes itself as per load requirements.


As the size of motor increases this slip keeps on reducing

e.g. for 0.5 KW motor slip is 5%
for 5 KW motor slip is 3 %
for 15 KW motor slip is 2.5 %
For 50 KW motor slip is 1.7%
and for 250 KW motor slip is 0.8%

As soon as motor started slip is 100% and it is keep on reducing as soon as speed increases and is minimum when motor is running at full speed. You can also say that as soon as slip decreased frequency decreases.

Also motor inductive reactance is dependent on slip as inductive reactance is maximum when motor is at standstill, as at that moment slip is maximum.

The inductive reactance will change with the slip since the rotor impedance is the phase sum of the constant resistance and the variable inductive reactance.

When the motor starts rotating the inductive reactance is high and impedance is mostly inductive. The rotor has a low lagging power factor. When the speed increases the inductive reactance goes down equaling the resistance.

There have been conflicting opinions and claims regarding the effect of replacing a "standard efficiency" motor with an "energy-efficient" motor on a centrifugal-type load.

Centrifugal pumps and fans impose what is often called a "cubed-exponential load" on the driver.

For such a pump or fan, torque varies approximately as the square of speed. Because, by definition, power varies directly with torque and with speed, for a centrifugal-type load, power varies approximately as the cube of speed - a small speed change produces a much larger change in power requirement. For example, a 1% increase in speed would bring a 3% increase in load: (1.01)3 = 1.03 Some engineers claim that an energy-efficient motor manifests most of its efficiency improvement at a lower slip speed; that is, as an increase - typically about 1% - in output speed. Because the 1% speed gain equates to a 3% horsepower requirement, they reason, the replacement energy-efficient motor may have to be 1 HP-size larger than the standard motor.

The contention does not fully account for the fact that the power reduction from using an energy-efficient motor is greater than the extra power required by the load - hence, there is a net energy

savings and the motor will run cooler, potentially extending insulation life.

Lighting System Designing Zones

There are following lighting Zones in Designing lighting system of any area:-

Zone Recommended Uses or Areas Zoning Considerations

LZ-0

Lighting Zone 0 should be applied to areas in which permanent lighting is not expected and when used, is limited in the amount of lighting and the period of operation.

LZ-0 typically includes undeveloped areas of open spaces, Parks , Outside area of any industry . Special review should be required for any permanent lighting in this zone.

LZ-1

Lighting Zone 1 pertains to areas that desire low lighting levels.

These typically residential communities with low Population, rural town centers, business parks, and other commercial or industrial/storage areas typically with limited night time activity.

This zone also Includes agricultural zone districts; rural residential zone districts; business parks; open space include preserves in developed areas.

LZ-2

Lighting Zone 2 pertains to areas with moderate lighting levels.

These typically include Highly Populated residential uses, institutional residential uses, schools, churches, hospitals, hotels/motels, commercial and/or businesses areas, playing fields and.

LZ-3

Lighting Zone 3 pertains to areas with moderately high lighting levels.

These typically include commercial corridors, high intensity suburban commercial areas, town centers, mixed use areas, industrial uses and shipping and rail yards with high night time activity, regional shopping malls, car dealerships, gas stations, Petrol Pumps and other nighttime active exterior retail areas.

LZ-4

Lighting zone 4 pertains to areas of very high ambient lighting levels. LZ-4 should only be used for special cases and is not appropriate for most cities. LZ-4 may be used for extremely unusual installations such as high density entertainment districts, and

heavy industrial uses.

Tube lights and its sizes; Tube light diameters

Tube lights are part of every industry and household. LED tube-lights are also coming in same sizes that of traditional lights.

Diameter of tube-light is described in 1/8 of the inch. So a T8 tube light is 1 inch diameter tube-light. This is obtained by simply multiplying 1/8 by numeric letter of description of tube light.  

Sizes of tube lights vary from T2 to T17.

Electronic ballasts, and T5 or T16 (⁵/₈" Ø or 15.875 mm Ø) for very small lamps which may even operate from a battery powered device.

Fluorescent tube diameter designation comparison
Tube diameter designations		Tube diameter measurements			Extra
Imperial-based	Metric-based	Inches Ø  (")		Millimeters Ø  (mm)	Socket	Notes
T4	N/A	4/8" Ø		12 mm Ø	G5 Bipin	Slim lamps, tube lengths may vary
T5	T16	5/8" Ø		15.875 mm Ø	G5	Supersedes T8, introduced in the 1990s
T8	T26	8/8" Ø	1" Ø	25.4 mm Ø	G13 bipin	From the 1930s. More common since the 1980s
T9	T29	9/8" Ø	11/8" Ø	28.575 mm Ø		Circular fluorescent tubes only
T12	T38	12/8" Ø	11/2" Ø	38.1 mm Ø	G13 bipin	Also from the 1930s. Not as efficient as new lamps
PG17	N/A	17/8" Ø	21/8" Ø	53.975 mm Ø		General Electric's

T8 tube-lights were most widely used in households were now days replaced with T5 tube-lights.

T5 Tube-Light length available is from 9 inch-21 inch and having power ranging from 2-15 watts.

T8 Tube lights length available are from 18 inch to 6 feet and power range is from 15 watt to 70 watts.

T12 Tube-lights length available are available from 18 inch to 8 feet and power range is from 15 W to 125 Watts.

1/8 of inch= 3.175 mm.

Applications of Tube-lights:-

(i)                T4 tube-lights are very compact and are having very easy installation, These are having very useful application in kitchen counters and worktops. Power consumption of these tube-lights is very low. Life of tube-lights is 9000 hours.

(ii)             T5 tube-lights are installed for efficiently lighting up Schools, factories, offices etc. Life of these tube lights is 20,000 hours. These lights have very low mercury content thus these have very minimum impact on environment. These lights uses specially designed blast which limits current into tube light. So prevents them from overloading. These blasts also enable them working above 20 kHz which gives instant start features to these tube lights.

(iii)           T8 tube-lights are most widely used tube lights and these are useful where there is need to see lot of details. These are useful in Stores, garages, offices, schools etc. These lights are having life more than 15,000 hours.

(iv)           T12 tube-lights are now vanishing out due to popularity of T8 lights. These are useful for lighting large areas such as offices and retail space.